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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
+ "http://www.w3.org/TR/html4/loose.dtd">
+ <html>
+ <head><title>A Tour Through TREE_RCU's Data Structures [LWN.net]</title>
+ <meta HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
+
+ <p>January 27, 2016</p>
+ <p>This article was contributed by Paul E. McKenney</p>
+
+<h3>Introduction</h3>
+
+This document describes RCU's major data structures and their relationship
+to each other.
+
+<ol>
+<li> <a href="#Data-Structure Relationships">
+ Data-Structure Relationships</a>
+<li> <a href="#The rcu_state Structure">
+ The <tt>rcu_state</tt> Structure</a>
+<li> <a href="#The rcu_node Structure">
+ The <tt>rcu_node</tt> Structure</a>
+<li> <a href="#The rcu_data Structure">
+ The <tt>rcu_data</tt> Structure</a>
+<li> <a href="#The rcu_dynticks Structure">
+ The <tt>rcu_dynticks</tt> Structure</a>
+<li> <a href="#The rcu_head Structure">
+ The <tt>rcu_head</tt> Structure</a>
+<li> <a href="#RCU-Specific Fields in the task_struct Structure">
+ RCU-Specific Fields in the <tt>task_struct</tt> Structure</a>
+<li> <a href="#Accessor Functions">
+ Accessor Functions</a>
+</ol>
+
+At the end we have the
+<a href="#Answers to Quick Quizzes">answers to the quick quizzes</a>.
+
+<h3><a name="Data-Structure Relationships">Data-Structure Relationships</a></h3>
+
+<p>RCU is for all intents and purposes a large state machine, and its
+data structures maintain the state in such a way as to allow RCU readers
+to execute extremely quickly, while also processing the RCU grace periods
+requested by updaters in an efficient and extremely scalable fashion.
+The efficiency and scalability of RCU updaters is provided primarily
+by a combining tree, as shown below:
+
+</p><p><img src="BigTreeClassicRCU.svg" alt="BigTreeClassicRCU.svg" width="30%">
+
+</p><p>This diagram shows an enclosing <tt>rcu_state</tt> structure
+containing a tree of <tt>rcu_node</tt> structures.
+Each leaf node of the <tt>rcu_node</tt> tree has up to 16
+<tt>rcu_data</tt> structures associated with it, so that there
+are <tt>NR_CPUS</tt> number of <tt>rcu_data</tt> structures,
+one for each possible CPU.
+This structure is adjusted at boot time, if needed, to handle the
+common case where <tt>nr_cpu_ids</tt> is much less than
+<tt>NR_CPUs</tt>.
+For example, a number of Linux distributions set <tt>NR_CPUs=4096</tt>,
+which results in a three-level <tt>rcu_node</tt> tree.
+If the actual hardware has only 16 CPUs, RCU will adjust itself
+at boot time, resulting in an <tt>rcu_node</tt> tree with only a single node.
+
+</p><p>The purpose of this combining tree is to allow per-CPU events
+such as quiescent states, dyntick-idle transitions,
+and CPU hotplug operations to be processed efficiently
+and scalably.
+Quiescent states are recorded by the per-CPU <tt>rcu_data</tt> structures,
+and other events are recorded by the leaf-level <tt>rcu_node</tt>
+structures.
+All of these events are combined at each level of the tree until finally
+grace periods are completed at the tree's root <tt>rcu_node</tt>
+structure.
+A grace period can be completed at the root once every CPU
+(or, in the case of <tt>CONFIG_PREEMPT_RCU</tt>, task)
+has passed through a quiescent state.
+Once a grace period has completed, record of that fact is propagated
+back down the tree.
+
+</p><p>As can be seen from the diagram, on a 64-bit system
+a two-level tree with 64 leaves can accommodate 1,024 CPUs, with a fanout
+of 64 at the root and a fanout of 16 at the leaves.
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Why isn't the fanout at the leaves also 64?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ Because there are more types of events that affect the leaf-level
+ <tt>rcu_node</tt> structures than further up the tree.
+ Therefore, if the leaf <tt>rcu_node</tt> structures have fanout of
+ 64, the contention on these structures' <tt>->structures</tt>
+ becomes excessive.
+ Experimentation on a wide variety of systems has shown that a fanout
+ of 16 works well for the leaves of the <tt>rcu_node</tt> tree.
+ </font>
+
+ <p><font color="ffffff">Of course, further experience with
+ systems having hundreds or thousands of CPUs may demonstrate
+ that the fanout for the non-leaf <tt>rcu_node</tt> structures
+ must also be reduced.
+ Such reduction can be easily carried out when and if it proves
+ necessary.
+ In the meantime, if you are using such a system and running into
+ contention problems on the non-leaf <tt>rcu_node</tt> structures,
+ you may use the <tt>CONFIG_RCU_FANOUT</tt> kernel configuration
+ parameter to reduce the non-leaf fanout as needed.
+ </font>
+
+ <p><font color="ffffff">Kernels built for systems with
+ strong NUMA characteristics might also need to adjust
+ <tt>CONFIG_RCU_FANOUT</tt> so that the domains of the
+ <tt>rcu_node</tt> structures align with hardware boundaries.
+ However, there has thus far been no need for this.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<p>If your system has more than 1,024 CPUs (or more than 512 CPUs on
+a 32-bit system), then RCU will automatically add more levels to the
+tree.
+For example, if you are crazy enough to build a 64-bit system with 65,536
+CPUs, RCU would configure the <tt>rcu_node</tt> tree as follows:
+
+</p><p><img src="HugeTreeClassicRCU.svg" alt="HugeTreeClassicRCU.svg" width="50%">
+
+</p><p>RCU currently permits up to a four-level tree, which on a 64-bit system
+accommodates up to 4,194,304 CPUs, though only a mere 524,288 CPUs for
+32-bit systems.
+On the other hand, you can set <tt>CONFIG_RCU_FANOUT</tt> to be
+as small as 2 if you wish, which would permit only 16 CPUs, which
+is useful for testing.
+
+</p><p>This multi-level combining tree allows us to get most of the
+performance and scalability
+benefits of partitioning, even though RCU grace-period detection is
+inherently a global operation.
+The trick here is that only the last CPU to report a quiescent state
+into a given <tt>rcu_node</tt> structure need advance to the <tt>rcu_node</tt>
+structure at the next level up the tree.
+This means that at the leaf-level <tt>rcu_node</tt> structure, only
+one access out of sixteen will progress up the tree.
+For the internal <tt>rcu_node</tt> structures, the situation is even
+more extreme: Only one access out of sixty-four will progress up
+the tree.
+Because the vast majority of the CPUs do not progress up the tree,
+the lock contention remains roughly constant up the tree.
+No matter how many CPUs there are in the system, at most 64 quiescent-state
+reports per grace period will progress all the way to the root
+<tt>rcu_node</tt> structure, thus ensuring that the lock contention
+on that root <tt>rcu_node</tt> structure remains acceptably low.
+
+</p><p>In effect, the combining tree acts like a big shock absorber,
+keeping lock contention under control at all tree levels regardless
+of the level of loading on the system.
+
+</p><p>The Linux kernel actually supports multiple flavors of RCU
+running concurrently, so RCU builds separate data structures for each
+flavor.
+For example, for <tt>CONFIG_TREE_RCU=y</tt> kernels, RCU provides
+rcu_sched and rcu_bh, as shown below:
+
+</p><p><img src="BigTreeClassicRCUBH.svg" alt="BigTreeClassicRCUBH.svg" width="33%">
+
+</p><p>Energy efficiency is increasingly important, and for that
+reason the Linux kernel provides <tt>CONFIG_NO_HZ_IDLE</tt>, which
+turns off the scheduling-clock interrupts on idle CPUs, which in
+turn allows those CPUs to attain deeper sleep states and to consume
+less energy.
+CPUs whose scheduling-clock interrupts have been turned off are
+said to be in <i>dyntick-idle mode</i>.
+RCU must handle dyntick-idle CPUs specially
+because RCU would otherwise wake up each CPU on every grace period,
+which would defeat the whole purpose of <tt>CONFIG_NO_HZ_IDLE</tt>.
+RCU uses the <tt>rcu_dynticks</tt> structure to track
+which CPUs are in dyntick idle mode, as shown below:
+
+</p><p><img src="BigTreeClassicRCUBHdyntick.svg" alt="BigTreeClassicRCUBHdyntick.svg" width="33%">
+
+</p><p>However, if a CPU is in dyntick-idle mode, it is in that mode
+for all flavors of RCU.
+Therefore, a single <tt>rcu_dynticks</tt> structure is allocated per
+CPU, and all of a given CPU's <tt>rcu_data</tt> structures share
+that <tt>rcu_dynticks</tt>, as shown in the figure.
+
+</p><p>Kernels built with <tt>CONFIG_PREEMPT_RCU</tt> support
+rcu_preempt in addition to rcu_sched and rcu_bh, as shown below:
+
+</p><p><img src="BigTreePreemptRCUBHdyntick.svg" alt="BigTreePreemptRCUBHdyntick.svg" width="35%">
+
+</p><p>RCU updaters wait for normal grace periods by registering
+RCU callbacks, either directly via <tt>call_rcu()</tt> and
+friends (namely <tt>call_rcu_bh()</tt> and <tt>call_rcu_sched()</tt>),
+there being a separate interface per flavor of RCU)
+or indirectly via <tt>synchronize_rcu()</tt> and friends.
+RCU callbacks are represented by <tt>rcu_head</tt> structures,
+which are queued on <tt>rcu_data</tt> structures while they are
+waiting for a grace period to elapse, as shown in the following figure:
+
+</p><p><img src="BigTreePreemptRCUBHdyntickCB.svg" alt="BigTreePreemptRCUBHdyntickCB.svg" width="40%">
+
+</p><p>This figure shows how <tt>TREE_RCU</tt>'s and
+<tt>PREEMPT_RCU</tt>'s major data structures are related.
+Lesser data structures will be introduced with the algorithms that
+make use of them.
+
+</p><p>Note that each of the data structures in the above figure has
+its own synchronization:
+
+<p><ol>
+<li> Each <tt>rcu_state</tt> structures has a lock and a mutex,
+ and some fields are protected by the corresponding root
+ <tt>rcu_node</tt> structure's lock.
+<li> Each <tt>rcu_node</tt> structure has a spinlock.
+<li> The fields in <tt>rcu_data</tt> are private to the corresponding
+ CPU, although a few can be read and written by other CPUs.
+<li> Similarly, the fields in <tt>rcu_dynticks</tt> are private
+ to the corresponding CPU, although a few can be read by
+ other CPUs.
+</ol>
+
+<p>It is important to note that different data structures can have
+very different ideas about the state of RCU at any given time.
+For but one example, awareness of the start or end of a given RCU
+grace period propagates slowly through the data structures.
+This slow propagation is absolutely necessary for RCU to have good
+read-side performance.
+If this balkanized implementation seems foreign to you, one useful
+trick is to consider each instance of these data structures to be
+a different person, each having the usual slightly different
+view of reality.
+
+</p><p>The general role of each of these data structures is as
+follows:
+
+</p><ol>
+<li> <tt>rcu_state</tt>:
+ This structure forms the interconnection between the
+ <tt>rcu_node</tt> and <tt>rcu_data</tt> structures,
+ tracks grace periods, serves as short-term repository
+ for callbacks orphaned by CPU-hotplug events,
+ maintains <tt>rcu_barrier()</tt> state,
+ tracks expedited grace-period state,
+ and maintains state used to force quiescent states when
+ grace periods extend too long,
+<li> <tt>rcu_node</tt>: This structure forms the combining
+ tree that propagates quiescent-state
+ information from the leaves to the root, and also propagates
+ grace-period information from the root to the leaves.
+ It provides local copies of the grace-period state in order
+ to allow this information to be accessed in a synchronized
+ manner without suffering the scalability limitations that
+ would otherwise be imposed by global locking.
+ In <tt>CONFIG_PREEMPT_RCU</tt> kernels, it manages the lists
+ of tasks that have blocked while in their current
+ RCU read-side critical section.
+ In <tt>CONFIG_PREEMPT_RCU</tt> with
+ <tt>CONFIG_RCU_BOOST</tt>, it manages the
+ per-<tt>rcu_node</tt> priority-boosting
+ kernel threads (kthreads) and state.
+ Finally, it records CPU-hotplug state in order to determine
+ which CPUs should be ignored during a given grace period.
+<li> <tt>rcu_data</tt>: This per-CPU structure is the
+ focus of quiescent-state detection and RCU callback queuing.
+ It also tracks its relationship to the corresponding leaf
+ <tt>rcu_node</tt> structure to allow more-efficient
+ propagation of quiescent states up the <tt>rcu_node</tt>
+ combining tree.
+ Like the <tt>rcu_node</tt> structure, it provides a local
+ copy of the grace-period information to allow for-free
+ synchronized
+ access to this information from the corresponding CPU.
+ Finally, this structure records past dyntick-idle state
+ for the corresponding CPU and also tracks statistics.
+<li> <tt>rcu_dynticks</tt>:
+ This per-CPU structure tracks the current dyntick-idle
+ state for the corresponding CPU.
+ Unlike the other three structures, the <tt>rcu_dynticks</tt>
+ structure is not replicated per RCU flavor.
+<li> <tt>rcu_head</tt>:
+ This structure represents RCU callbacks, and is the
+ only structure allocated and managed by RCU users.
+ The <tt>rcu_head</tt> structure is normally embedded
+ within the RCU-protected data structure.
+</ol>
+
+<p>If all you wanted from this article was a general notion of how
+RCU's data structures are related, you are done.
+Otherwise, each of the following sections give more details on
+the <tt>rcu_state</tt>, <tt>rcu_node</tt>, <tt>rcu_data</tt>,
+and <tt>rcu_dynticks</tt> data structures.
+
+<h3><a name="The rcu_state Structure">
+The <tt>rcu_state</tt> Structure</a></h3>
+
+<p>The <tt>rcu_state</tt> structure is the base structure that
+represents a flavor of RCU.
+This structure forms the interconnection between the
+<tt>rcu_node</tt> and <tt>rcu_data</tt> structures,
+tracks grace periods, contains the lock used to
+synchronize with CPU-hotplug events,
+and maintains state used to force quiescent states when
+grace periods extend too long,
+
+</p><p>A few of the <tt>rcu_state</tt> structure's fields are discussed,
+singly and in groups, in the following sections.
+The more specialized fields are covered in the discussion of their
+use.
+
+<h5>Relationship to rcu_node and rcu_data Structures</h5>
+
+This portion of the <tt>rcu_state</tt> structure is declared
+as follows:
+
+<pre>
+ 1 struct rcu_node node[NUM_RCU_NODES];
+ 2 struct rcu_node *level[NUM_RCU_LVLS + 1];
+ 3 struct rcu_data __percpu *rda;
+</pre>
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Wait a minute!
+ You said that the <tt>rcu_node</tt> structures formed a tree,
+ but they are declared as a flat array!
+ What gives?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ The tree is laid out in the array.
+ The first node In the array is the head, the next set of nodes in the
+ array are children of the head node, and so on until the last set of
+ nodes in the array are the leaves.
+ </font>
+
+ <p><font color="ffffff">See the following diagrams to see how
+ this works.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<p>The <tt>rcu_node</tt> tree is embedded into the
+<tt>->node[]</tt> array as shown in the following figure:
+
+</p><p><img src="TreeMapping.svg" alt="TreeMapping.svg" width="40%">
+
+</p><p>One interesting consequence of this mapping is that a
+breadth-first traversal of the tree is implemented as a simple
+linear scan of the array, which is in fact what the
+<tt>rcu_for_each_node_breadth_first()</tt> macro does.
+This macro is used at the beginning and ends of grace periods.
+
+</p><p>Each entry of the <tt>->level</tt> array references
+the first <tt>rcu_node</tt> structure on the corresponding level
+of the tree, for example, as shown below:
+
+</p><p><img src="TreeMappingLevel.svg" alt="TreeMappingLevel.svg" width="40%">
+
+</p><p>The zero<sup>th</sup> element of the array references the root
+<tt>rcu_node</tt> structure, the first element references the
+first child of the root <tt>rcu_node</tt>, and finally the second
+element references the first leaf <tt>rcu_node</tt> structure.
+
+</p><p>For whatever it is worth, if you draw the tree to be tree-shaped
+rather than array-shaped, it is easy to draw a planar representation:
+
+</p><p><img src="TreeLevel.svg" alt="TreeLevel.svg" width="60%">
+
+</p><p>Finally, the <tt>->rda</tt> field references a per-CPU
+pointer to the corresponding CPU's <tt>rcu_data</tt> structure.
+
+</p><p>All of these fields are constant once initialization is complete,
+and therefore need no protection.
+
+<h5>Grace-Period Tracking</h5>
+
+<p>This portion of the <tt>rcu_state</tt> structure is declared
+as follows:
+
+<pre>
+ 1 unsigned long gpnum;
+ 2 unsigned long completed;
+</pre>
+
+<p>RCU grace periods are numbered, and
+the <tt>->gpnum</tt> field contains the number of the grace
+period that started most recently.
+The <tt>->completed</tt> field contains the number of the
+grace period that completed most recently.
+If the two fields are equal, the RCU grace period that most recently
+started has already completed, and therefore the corresponding
+flavor of RCU is idle.
+If <tt>->gpnum</tt> is one greater than <tt>->completed</tt>,
+then <tt>->gpnum</tt> gives the number of the current RCU
+grace period, which has not yet completed.
+Any other combination of values indicates that something is broken.
+These two fields are protected by the root <tt>rcu_node</tt>'s
+<tt>->lock</tt> field.
+
+</p><p>There are <tt>->gpnum</tt> and <tt>->completed</tt> fields
+in the <tt>rcu_node</tt> and <tt>rcu_data</tt> structures
+as well.
+The fields in the <tt>rcu_state</tt> structure represent the
+most current values, and those of the other structures are compared
+in order to detect the start of a new grace period in a distributed
+fashion.
+The values flow from <tt>rcu_state</tt> to <tt>rcu_node</tt>
+(down the tree from the root to the leaves) to <tt>rcu_data</tt>.
+
+<h5>Miscellaneous</h5>
+
+<p>This portion of the <tt>rcu_state</tt> structure is declared
+as follows:
+
+<pre>
+ 1 unsigned long gp_max;
+ 2 char abbr;
+ 3 char *name;
+</pre>
+
+<p>The <tt>->gp_max</tt> field tracks the duration of the longest
+grace period in jiffies.
+It is protected by the root <tt>rcu_node</tt>'s <tt>->lock</tt>.
+
+<p>The <tt>->name</tt> field points to the name of the RCU flavor
+(for example, “rcu_sched”), and is constant.
+The <tt>->abbr</tt> field contains a one-character abbreviation,
+for example, “s” for RCU-sched.
+
+<h3><a name="The rcu_node Structure">
+The <tt>rcu_node</tt> Structure</a></h3>
+
+<p>The <tt>rcu_node</tt> structures form the combining
+tree that propagates quiescent-state
+information from the leaves to the root and also that propagates
+grace-period information from the root down to the leaves.
+They provides local copies of the grace-period state in order
+to allow this information to be accessed in a synchronized
+manner without suffering the scalability limitations that
+would otherwise be imposed by global locking.
+In <tt>CONFIG_PREEMPT_RCU</tt> kernels, they manage the lists
+of tasks that have blocked while in their current
+RCU read-side critical section.
+In <tt>CONFIG_PREEMPT_RCU</tt> with
+<tt>CONFIG_RCU_BOOST</tt>, they manage the
+per-<tt>rcu_node</tt> priority-boosting
+kernel threads (kthreads) and state.
+Finally, they record CPU-hotplug state in order to determine
+which CPUs should be ignored during a given grace period.
+
+</p><p>The <tt>rcu_node</tt> structure's fields are discussed,
+singly and in groups, in the following sections.
+
+<h5>Connection to Combining Tree</h5>
+
+<p>This portion of the <tt>rcu_node</tt> structure is declared
+as follows:
+
+<pre>
+ 1 struct rcu_node *parent;
+ 2 u8 level;
+ 3 u8 grpnum;
+ 4 unsigned long grpmask;
+ 5 int grplo;
+ 6 int grphi;
+</pre>
+
+<p>The <tt>->parent</tt> pointer references the <tt>rcu_node</tt>
+one level up in the tree, and is <tt>NULL</tt> for the root
+<tt>rcu_node</tt>.
+The RCU implementation makes heavy use of this field to push quiescent
+states up the tree.
+The <tt>->level</tt> field gives the level in the tree, with
+the root being at level zero, its children at level one, and so on.
+The <tt>->grpnum</tt> field gives this node's position within
+the children of its parent, so this number can range between 0 and 31
+on 32-bit systems and between 0 and 63 on 64-bit systems.
+The <tt>->level</tt> and <tt>->grpnum</tt> fields are
+used only during initialization and for tracing.
+The <tt>->grpmask</tt> field is the bitmask counterpart of
+<tt>->grpnum</tt>, and therefore always has exactly one bit set.
+This mask is used to clear the bit corresponding to this <tt>rcu_node</tt>
+structure in its parent's bitmasks, which are described later.
+Finally, the <tt>->grplo</tt> and <tt>->grphi</tt> fields
+contain the lowest and highest numbered CPU served by this
+<tt>rcu_node</tt> structure, respectively.
+
+</p><p>All of these fields are constant, and thus do not require any
+synchronization.
+
+<h5>Synchronization</h5>
+
+<p>This field of the <tt>rcu_node</tt> structure is declared
+as follows:
+
+<pre>
+ 1 raw_spinlock_t lock;
+</pre>
+
+<p>This field is used to protect the remaining fields in this structure,
+unless otherwise stated.
+That said, all of the fields in this structure can be accessed without
+locking for tracing purposes.
+Yes, this can result in confusing traces, but better some tracing confusion
+than to be heisenbugged out of existence.
+
+<h5>Grace-Period Tracking</h5>
+
+<p>This portion of the <tt>rcu_node</tt> structure is declared
+as follows:
+
+<pre>
+ 1 unsigned long gpnum;
+ 2 unsigned long completed;
+</pre>
+
+<p>These fields are the counterparts of the fields of the same name in
+the <tt>rcu_state</tt> structure.
+They each may lag up to one behind their <tt>rcu_state</tt>
+counterparts.
+If a given <tt>rcu_node</tt> structure's <tt>->gpnum</tt> and
+<tt>->complete</tt> fields are equal, then this <tt>rcu_node</tt>
+structure believes that RCU is idle.
+Otherwise, as with the <tt>rcu_state</tt> structure,
+the <tt>->gpnum</tt> field will be one greater than the
+<tt>->complete</tt> fields, with <tt>->gpnum</tt>
+indicating which grace period this <tt>rcu_node</tt> believes
+is still being waited for.
+
+</p><p>The <tt>>gpnum</tt> field of each <tt>rcu_node</tt>
+structure is updated at the beginning
+of each grace period, and the <tt>->completed</tt> fields are
+updated at the end of each grace period.
+
+<h5>Quiescent-State Tracking</h5>
+
+<p>These fields manage the propagation of quiescent states up the
+combining tree.
+
+</p><p>This portion of the <tt>rcu_node</tt> structure has fields
+as follows:
+
+<pre>
+ 1 unsigned long qsmask;
+ 2 unsigned long expmask;
+ 3 unsigned long qsmaskinit;
+ 4 unsigned long expmaskinit;
+</pre>
+
+<p>The <tt>->qsmask</tt> field tracks which of this
+<tt>rcu_node</tt> structure's children still need to report
+quiescent states for the current normal grace period.
+Such children will have a value of 1 in their corresponding bit.
+Note that the leaf <tt>rcu_node</tt> structures should be
+thought of as having <tt>rcu_data</tt> structures as their
+children.
+Similarly, the <tt>->expmask</tt> field tracks which
+of this <tt>rcu_node</tt> structure's children still need to report
+quiescent states for the current expedited grace period.
+An expedited grace period has
+the same conceptual properties as a normal grace period, but the
+expedited implementation accepts extreme CPU overhead to obtain
+much lower grace-period latency, for example, consuming a few
+tens of microseconds worth of CPU time to reduce grace-period
+duration from milliseconds to tens of microseconds.
+The <tt>->qsmaskinit</tt> field tracks which of this
+<tt>rcu_node</tt> structure's children cover for at least
+one online CPU.
+This mask is used to initialize <tt>->qsmask</tt>,
+and <tt>->expmaskinit</tt> is used to initialize
+<tt>->expmask</tt> and the beginning of the
+normal and expedited grace periods, respectively.
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Why are these bitmasks protected by locking?
+ Come on, haven't you heard of atomic instructions???
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ Lockless grace-period computation! Such a tantalizing possibility!
+ </font>
+
+ <p><font color="ffffff">But consider the following sequence of events:
+ </font>
+
+ <ol>
+ <li> <font color="ffffff">CPU 0 has been in dyntick-idle
+ mode for quite some time.
+ When it wakes up, it notices that the current RCU
+ grace period needs it to report in, so it sets a
+ flag where the scheduling clock interrupt will find it.
+ </font><p>
+ <li> <font color="ffffff">Meanwhile, CPU 1 is running
+ <tt>force_quiescent_state()</tt>,
+ and notices that CPU 0 has been in dyntick idle mode,
+ which qualifies as an extended quiescent state.
+ </font><p>
+ <li> <font color="ffffff">CPU 0's scheduling clock
+ interrupt fires in the
+ middle of an RCU read-side critical section, and notices
+ that the RCU core needs something, so commences RCU softirq
+ processing.
+ </font>
+ <p>
+ <li> <font color="ffffff">CPU 0's softirq handler
+ executes and is just about ready
+ to report its quiescent state up the <tt>rcu_node</tt>
+ tree.
+ </font><p>
+ <li> <font color="ffffff">But CPU 1 beats it to the punch,
+ completing the current
+ grace period and starting a new one.
+ </font><p>
+ <li> <font color="ffffff">CPU 0 now reports its quiescent
+ state for the wrong
+ grace period.
+ That grace period might now end before the RCU read-side
+ critical section.
+ If that happens, disaster will ensue.
+ </font>
+ </ol>
+
+ <p><font color="ffffff">So the locking is absolutely required in
+ order to coordinate
+ clearing of the bits with the grace-period numbers in
+ <tt>->gpnum</tt> and <tt>->completed</tt>.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<h5>Blocked-Task Management</h5>
+
+<p><tt>PREEMPT_RCU</tt> allows tasks to be preempted in the
+midst of their RCU read-side critical sections, and these tasks
+must be tracked explicitly.
+The details of exactly why and how they are tracked will be covered
+in a separate article on RCU read-side processing.
+For now, it is enough to know that the <tt>rcu_node</tt>
+structure tracks them.
+
+<pre>
+ 1 struct list_head blkd_tasks;
+ 2 struct list_head *gp_tasks;
+ 3 struct list_head *exp_tasks;
+ 4 bool wait_blkd_tasks;
+</pre>
+
+<p>The <tt>->blkd_tasks</tt> field is a list header for
+the list of blocked and preempted tasks.
+As tasks undergo context switches within RCU read-side critical
+sections, their <tt>task_struct</tt> structures are enqueued
+(via the <tt>task_struct</tt>'s <tt>->rcu_node_entry</tt>
+field) onto the head of the <tt>->blkd_tasks</tt> list for the
+leaf <tt>rcu_node</tt> structure corresponding to the CPU
+on which the outgoing context switch executed.
+As these tasks later exit their RCU read-side critical sections,
+they remove themselves from the list.
+This list is therefore in reverse time order, so that if one of the tasks
+is blocking the current grace period, all subsequent tasks must
+also be blocking that same grace period.
+Therefore, a single pointer into this list suffices to track
+all tasks blocking a given grace period.
+That pointer is stored in <tt>->gp_tasks</tt> for normal
+grace periods and in <tt>->exp_tasks</tt> for expedited
+grace periods.
+These last two fields are <tt>NULL</tt> if either there is
+no grace period in flight or if there are no blocked tasks
+preventing that grace period from completing.
+If either of these two pointers is referencing a task that
+removes itself from the <tt>->blkd_tasks</tt> list,
+then that task must advance the pointer to the next task on
+the list, or set the pointer to <tt>NULL</tt> if there
+are no subsequent tasks on the list.
+
+</p><p>For example, suppose that tasks T1, T2, and T3 are
+all hard-affinitied to the largest-numbered CPU in the system.
+Then if task T1 blocked in an RCU read-side
+critical section, then an expedited grace period started,
+then task T2 blocked in an RCU read-side critical section,
+then a normal grace period started, and finally task 3 blocked
+in an RCU read-side critical section, then the state of the
+last leaf <tt>rcu_node</tt> structure's blocked-task list
+would be as shown below:
+
+</p><p><img src="blkd_task.svg" alt="blkd_task.svg" width="60%">
+
+</p><p>Task T1 is blocking both grace periods, task T2 is
+blocking only the normal grace period, and task T3 is blocking
+neither grace period.
+Note that these tasks will not remove themselves from this list
+immediately upon resuming execution.
+They will instead remain on the list until they execute the outermost
+<tt>rcu_read_unlock()</tt> that ends their RCU read-side critical
+section.
+
+<p>
+The <tt>->wait_blkd_tasks</tt> field indicates whether or not
+the current grace period is waiting on a blocked task.
+
+<h5>Sizing the <tt>rcu_node</tt> Array</h5>
+
+<p>The <tt>rcu_node</tt> array is sized via a series of
+C-preprocessor expressions as follows:
+
+<pre>
+ 1 #ifdef CONFIG_RCU_FANOUT
+ 2 #define RCU_FANOUT CONFIG_RCU_FANOUT
+ 3 #else
+ 4 # ifdef CONFIG_64BIT
+ 5 # define RCU_FANOUT 64
+ 6 # else
+ 7 # define RCU_FANOUT 32
+ 8 # endif
+ 9 #endif
+10
+11 #ifdef CONFIG_RCU_FANOUT_LEAF
+12 #define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF
+13 #else
+14 # ifdef CONFIG_64BIT
+15 # define RCU_FANOUT_LEAF 64
+16 # else
+17 # define RCU_FANOUT_LEAF 32
+18 # endif
+19 #endif
+20
+21 #define RCU_FANOUT_1 (RCU_FANOUT_LEAF)
+22 #define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT)
+23 #define RCU_FANOUT_3 (RCU_FANOUT_2 * RCU_FANOUT)
+24 #define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT)
+25
+26 #if NR_CPUS <= RCU_FANOUT_1
+27 # define RCU_NUM_LVLS 1
+28 # define NUM_RCU_LVL_0 1
+29 # define NUM_RCU_NODES NUM_RCU_LVL_0
+30 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 }
+31 # define RCU_NODE_NAME_INIT { "rcu_node_0" }
+32 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" }
+33 # define RCU_EXP_NAME_INIT { "rcu_node_exp_0" }
+34 #elif NR_CPUS <= RCU_FANOUT_2
+35 # define RCU_NUM_LVLS 2
+36 # define NUM_RCU_LVL_0 1
+37 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
+38 # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1)
+39 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 }
+40 # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" }
+41 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" }
+42 # define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1" }
+43 #elif NR_CPUS <= RCU_FANOUT_3
+44 # define RCU_NUM_LVLS 3
+45 # define NUM_RCU_LVL_0 1
+46 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
+47 # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
+48 # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2)
+49 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 }
+50 # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" }
+51 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" }
+52 # define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2" }
+53 #elif NR_CPUS <= RCU_FANOUT_4
+54 # define RCU_NUM_LVLS 4
+55 # define NUM_RCU_LVL_0 1
+56 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3)
+57 # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
+58 # define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
+59 # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3)
+60 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 }
+61 # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" }
+62 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" }
+63 # define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2", "rcu_node_exp_3" }
+64 #else
+65 # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
+66 #endif
+</pre>
+
+<p>The maximum number of levels in the <tt>rcu_node</tt> structure
+is currently limited to four, as specified by lines 21-24
+and the structure of the subsequent “if” statement.
+For 32-bit systems, this allows 16*32*32*32=524,288 CPUs, which
+should be sufficient for the next few years at least.
+For 64-bit systems, 16*64*64*64=4,194,304 CPUs is allowed, which
+should see us through the next decade or so.
+This four-level tree also allows kernels built with
+<tt>CONFIG_RCU_FANOUT=8</tt> to support up to 4096 CPUs,
+which might be useful in very large systems having eight CPUs per
+socket (but please note that no one has yet shown any measurable
+performance degradation due to misaligned socket and <tt>rcu_node</tt>
+boundaries).
+In addition, building kernels with a full four levels of <tt>rcu_node</tt>
+tree permits better testing of RCU's combining-tree code.
+
+</p><p>The <tt>RCU_FANOUT</tt> symbol controls how many children
+are permitted at each non-leaf level of the <tt>rcu_node</tt> tree.
+If the <tt>CONFIG_RCU_FANOUT</tt> Kconfig option is not specified,
+it is set based on the word size of the system, which is also
+the Kconfig default.
+
+</p><p>The <tt>RCU_FANOUT_LEAF</tt> symbol controls how many CPUs are
+handled by each leaf <tt>rcu_node</tt> structure.
+Experience has shown that allowing a given leaf <tt>rcu_node</tt>
+structure to handle 64 CPUs, as permitted by the number of bits in
+the <tt>->qsmask</tt> field on a 64-bit system, results in
+excessive contention for the leaf <tt>rcu_node</tt> structures'
+<tt>->lock</tt> fields.
+The number of CPUs per leaf <tt>rcu_node</tt> structure is therefore
+limited to 16 given the default value of <tt>CONFIG_RCU_FANOUT_LEAF</tt>.
+If <tt>CONFIG_RCU_FANOUT_LEAF</tt> is unspecified, the value
+selected is based on the word size of the system, just as for
+<tt>CONFIG_RCU_FANOUT</tt>.
+Lines 11-19 perform this computation.
+
+</p><p>Lines 21-24 compute the maximum number of CPUs supported by
+a single-level (which contains a single <tt>rcu_node</tt> structure),
+two-level, three-level, and four-level <tt>rcu_node</tt> tree,
+respectively, given the fanout specified by <tt>RCU_FANOUT</tt>
+and <tt>RCU_FANOUT_LEAF</tt>.
+These numbers of CPUs are retained in the
+<tt>RCU_FANOUT_1</tt>,
+<tt>RCU_FANOUT_2</tt>,
+<tt>RCU_FANOUT_3</tt>, and
+<tt>RCU_FANOUT_4</tt>
+C-preprocessor variables, respectively.
+
+</p><p>These variables are used to control the C-preprocessor <tt>#if</tt>
+statement spanning lines 26-66 that computes the number of
+<tt>rcu_node</tt> structures required for each level of the tree,
+as well as the number of levels required.
+The number of levels is placed in the <tt>NUM_RCU_LVLS</tt>
+C-preprocessor variable by lines 27, 35, 44, and 54.
+The number of <tt>rcu_node</tt> structures for the topmost level
+of the tree is always exactly one, and this value is unconditionally
+placed into <tt>NUM_RCU_LVL_0</tt> by lines 28, 36, 45, and 55.
+The rest of the levels (if any) of the <tt>rcu_node</tt> tree
+are computed by dividing the maximum number of CPUs by the
+fanout supported by the number of levels from the current level down,
+rounding up. This computation is performed by lines 37,
+46-47, and 56-58.
+Lines 31-33, 40-42, 50-52, and 62-63 create initializers
+for lockdep lock-class names.
+Finally, lines 64-66 produce an error if the maximum number of
+CPUs is too large for the specified fanout.
+
+<h3><a name="The rcu_data Structure">
+The <tt>rcu_data</tt> Structure</a></h3>
+
+<p>The <tt>rcu_data</tt> maintains the per-CPU state for the
+corresponding flavor of RCU.
+The fields in this structure may be accessed only from the corresponding
+CPU (and from tracing) unless otherwise stated.
+This structure is the
+focus of quiescent-state detection and RCU callback queuing.
+It also tracks its relationship to the corresponding leaf
+<tt>rcu_node</tt> structure to allow more-efficient
+propagation of quiescent states up the <tt>rcu_node</tt>
+combining tree.
+Like the <tt>rcu_node</tt> structure, it provides a local
+copy of the grace-period information to allow for-free
+synchronized
+access to this information from the corresponding CPU.
+Finally, this structure records past dyntick-idle state
+for the corresponding CPU and also tracks statistics.
+
+</p><p>The <tt>rcu_data</tt> structure's fields are discussed,
+singly and in groups, in the following sections.
+
+<h5>Connection to Other Data Structures</h5>
+
+<p>This portion of the <tt>rcu_data</tt> structure is declared
+as follows:
+
+<pre>
+ 1 int cpu;
+ 2 struct rcu_state *rsp;
+ 3 struct rcu_node *mynode;
+ 4 struct rcu_dynticks *dynticks;
+ 5 unsigned long grpmask;
+ 6 bool beenonline;
+</pre>
+
+<p>The <tt>->cpu</tt> field contains the number of the
+corresponding CPU, the <tt>->rsp</tt> pointer references
+the corresponding <tt>rcu_state</tt> structure (and is most frequently
+used to locate the name of the corresponding flavor of RCU for tracing),
+and the <tt>->mynode</tt> field references the corresponding
+<tt>rcu_node</tt> structure.
+The <tt>->mynode</tt> is used to propagate quiescent states
+up the combining tree.
+<p>The <tt>->dynticks</tt> pointer references the
+<tt>rcu_dynticks</tt> structure corresponding to this
+CPU.
+Recall that a single per-CPU instance of the <tt>rcu_dynticks</tt>
+structure is shared among all flavors of RCU.
+These first four fields are constant and therefore require not
+synchronization.
+
+</p><p>The <tt>->grpmask</tt> field indicates the bit in
+the <tt>->mynode->qsmask</tt> corresponding to this
+<tt>rcu_data</tt> structure, and is also used when propagating
+quiescent states.
+The <tt>->beenonline</tt> flag is set whenever the corresponding
+CPU comes online, which means that the debugfs tracing need not dump
+out any <tt>rcu_data</tt> structure for which this flag is not set.
+
+<h5>Quiescent-State and Grace-Period Tracking</h5>
+
+<p>This portion of the <tt>rcu_data</tt> structure is declared
+as follows:
+
+<pre>
+ 1 unsigned long completed;
+ 2 unsigned long gpnum;
+ 3 bool cpu_no_qs;
+ 4 bool core_needs_qs;
+ 5 bool gpwrap;
+ 6 unsigned long rcu_qs_ctr_snap;
+</pre>
+
+<p>The <tt>completed</tt> and <tt>gpnum</tt>
+fields are the counterparts of the fields of the same name
+in the <tt>rcu_state</tt> and <tt>rcu_node</tt> structures.
+They may each lag up to one behind their <tt>rcu_node</tt>
+counterparts, but in <tt>CONFIG_NO_HZ_IDLE</tt> and
+<tt>CONFIG_NO_HZ_FULL</tt> kernels can lag
+arbitrarily far behind for CPUs in dyntick-idle mode (but these counters
+will catch up upon exit from dyntick-idle mode).
+If a given <tt>rcu_data</tt> structure's <tt>->gpnum</tt> and
+<tt>->complete</tt> fields are equal, then this <tt>rcu_data</tt>
+structure believes that RCU is idle.
+Otherwise, as with the <tt>rcu_state</tt> and <tt>rcu_node</tt>
+structure,
+the <tt>->gpnum</tt> field will be one greater than the
+<tt>->complete</tt> fields, with <tt>->gpnum</tt>
+indicating which grace period this <tt>rcu_data</tt> believes
+is still being waited for.
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ All this replication of the grace period numbers can only cause
+ massive confusion.
+ Why not just keep a global pair of counters and be done with it???
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ Because if there was only a single global pair of grace-period
+ numbers, there would need to be a single global lock to allow
+ safely accessing and updating them.
+ And if we are not going to have a single global lock, we need
+ to carefully manage the numbers on a per-node basis.
+ Recall from the answer to a previous Quick Quiz that the consequences
+ of applying a previously sampled quiescent state to the wrong
+ grace period are quite severe.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<p>The <tt>->cpu_no_qs</tt> flag indicates that the
+CPU has not yet passed through a quiescent state,
+while the <tt>->core_needs_qs</tt> flag indicates that the
+RCU core needs a quiescent state from the corresponding CPU.
+The <tt>->gpwrap</tt> field indicates that the corresponding
+CPU has remained idle for so long that the <tt>completed</tt>
+and <tt>gpnum</tt> counters are in danger of overflow, which
+will cause the CPU to disregard the values of its counters on
+its next exit from idle.
+Finally, the <tt>rcu_qs_ctr_snap</tt> field is used to detect
+cases where a given operation has resulted in a quiescent state
+for all flavors of RCU, for example, <tt>cond_resched_rcu_qs()</tt>.
+
+<h5>RCU Callback Handling</h5>
+
+<p>In the absence of CPU-hotplug events, RCU callbacks are invoked by
+the same CPU that registered them.
+This is strictly a cache-locality optimization: callbacks can and
+do get invoked on CPUs other than the one that registered them.
+After all, if the CPU that registered a given callback has gone
+offline before the callback can be invoked, there really is no other
+choice.
+
+</p><p>This portion of the <tt>rcu_data</tt> structure is declared
+as follows:
+
+<pre>
+ 1 struct rcu_head *nxtlist;
+ 2 struct rcu_head **nxttail[RCU_NEXT_SIZE];
+ 3 unsigned long nxtcompleted[RCU_NEXT_SIZE];
+ 4 long qlen_lazy;
+ 5 long qlen;
+ 6 long qlen_last_fqs_check;
+ 7 unsigned long n_force_qs_snap;
+ 8 unsigned long n_cbs_invoked;
+ 9 unsigned long n_cbs_orphaned;
+10 unsigned long n_cbs_adopted;
+11 long blimit;
+</pre>
+
+<p>The <tt>->nxtlist</tt> pointer and the
+<tt>->nxttail[]</tt> array form a four-segment list with
+older callbacks near the head and newer ones near the tail.
+Each segment contains callbacks with the corresponding relationship
+to the current grace period.
+The pointer out of the end of each of the four segments is referenced
+by the element of the <tt>->nxttail[]</tt> array indexed by
+<tt>RCU_DONE_TAIL</tt> (for callbacks handled by a prior grace period),
+<tt>RCU_WAIT_TAIL</tt> (for callbacks waiting on the current grace period),
+<tt>RCU_NEXT_READY_TAIL</tt> (for callbacks that will wait on the next
+grace period), and
+<tt>RCU_NEXT_TAIL</tt> (for callbacks that are not yet associated
+with a specific grace period)
+respectively, as shown in the following figure.
+
+</p><p><img src="nxtlist.svg" alt="nxtlist.svg" width="40%">
+
+</p><p>In this figure, the <tt>->nxtlist</tt> pointer references the
+first
+RCU callback in the list.
+The <tt>->nxttail[RCU_DONE_TAIL]</tt> array element references
+the <tt>->nxtlist</tt> pointer itself, indicating that none
+of the callbacks is ready to invoke.
+The <tt>->nxttail[RCU_WAIT_TAIL]</tt> array element references callback
+CB 2's <tt>->next</tt> pointer, which indicates that
+CB 1 and CB 2 are both waiting on the current grace period.
+The <tt>->nxttail[RCU_NEXT_READY_TAIL]</tt> array element
+references the same RCU callback that <tt>->nxttail[RCU_WAIT_TAIL]</tt>
+does, which indicates that there are no callbacks waiting on the next
+RCU grace period.
+The <tt>->nxttail[RCU_NEXT_TAIL]</tt> array element references
+CB 4's <tt>->next</tt> pointer, indicating that all the
+remaining RCU callbacks have not yet been assigned to an RCU grace
+period.
+Note that the <tt>->nxttail[RCU_NEXT_TAIL]</tt> array element
+always references the last RCU callback's <tt>->next</tt> pointer
+unless the callback list is empty, in which case it references
+the <tt>->nxtlist</tt> pointer.
+
+</p><p>CPUs advance their callbacks from the
+<tt>RCU_NEXT_TAIL</tt> to the <tt>RCU_NEXT_READY_TAIL</tt> to the
+<tt>RCU_WAIT_TAIL</tt> to the <tt>RCU_DONE_TAIL</tt> list segments
+as grace periods advance.
+The CPU advances the callbacks in its <tt>rcu_data</tt> structure
+whenever it notices that another RCU grace period has completed.
+The CPU detects the completion of an RCU grace period by noticing
+that the value of its <tt>rcu_data</tt> structure's
+<tt>->completed</tt> field differs from that of its leaf
+<tt>rcu_node</tt> structure.
+Recall that each <tt>rcu_node</tt> structure's
+<tt>->completed</tt> field is updated at the end of each
+grace period.
+
+</p><p>The <tt>->nxtcompleted[]</tt> array records grace-period
+numbers corresponding to the list segments.
+This allows CPUs that go idle for extended periods to determine
+which of their callbacks are ready to be invoked after reawakening.
+
+</p><p>The <tt>->qlen</tt> counter contains the number of
+callbacks in <tt>->nxtlist</tt>, and the
+<tt>->qlen_lazy</tt> contains the number of those callbacks that
+are known to only free memory, and whose invocation can therefore
+be safely deferred.
+The <tt>->qlen_last_fqs_check</tt> and
+<tt>->n_force_qs_snap</tt> coordinate the forcing of quiescent
+states from <tt>call_rcu()</tt> and friends when callback
+lists grow excessively long.
+
+</p><p>The <tt>->n_cbs_invoked</tt>,
+<tt>->n_cbs_orphaned</tt>, and <tt>->n_cbs_adopted</tt>
+fields count the number of callbacks invoked,
+sent to other CPUs when this CPU goes offline,
+and received from other CPUs when those other CPUs go offline.
+Finally, the <tt>->blimit</tt> counter is the maximum number of
+RCU callbacks that may be invoked at a given time.
+
+<h5>Dyntick-Idle Handling</h5>
+
+<p>This portion of the <tt>rcu_data</tt> structure is declared
+as follows:
+
+<pre>
+ 1 int dynticks_snap;
+ 2 unsigned long dynticks_fqs;
+</pre>
+
+The <tt>->dynticks_snap</tt> field is used to take a snapshot
+of the corresponding CPU's dyntick-idle state when forcing
+quiescent states, and is therefore accessed from other CPUs.
+Finally, the <tt>->dynticks_fqs</tt> field is used to
+count the number of times this CPU is determined to be in
+dyntick-idle state, and is used for tracing and debugging purposes.
+
+<h3><a name="The rcu_dynticks Structure">
+The <tt>rcu_dynticks</tt> Structure</a></h3>
+
+<p>The <tt>rcu_dynticks</tt> maintains the per-CPU dyntick-idle state
+for the corresponding CPU.
+Unlike the other structures, <tt>rcu_dynticks</tt> is not
+replicated over the different flavors of RCU.
+The fields in this structure may be accessed only from the corresponding
+CPU (and from tracing) unless otherwise stated.
+Its fields are as follows:
+
+<pre>
+ 1 int dynticks_nesting;
+ 2 int dynticks_nmi_nesting;
+ 3 atomic_t dynticks;
+</pre>
+
+<p>The <tt>->dynticks_nesting</tt> field counts the
+nesting depth of normal interrupts.
+In addition, this counter is incremented when exiting dyntick-idle
+mode and decremented when entering it.
+This counter can therefore be thought of as counting the number
+of reasons why this CPU cannot be permitted to enter dyntick-idle
+mode, aside from non-maskable interrupts (NMIs).
+NMIs are counted by the <tt>->dynticks_nmi_nesting</tt>
+field, except that NMIs that interrupt non-dyntick-idle execution
+are not counted.
+
+</p><p>Finally, the <tt>->dynticks</tt> field counts the corresponding
+CPU's transitions to and from dyntick-idle mode, so that this counter
+has an even value when the CPU is in dyntick-idle mode and an odd
+value otherwise.
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Why not just count all NMIs?
+ Wouldn't that be simpler and less error prone?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ It seems simpler only until you think hard about how to go about
+ updating the <tt>rcu_dynticks</tt> structure's
+ <tt>->dynticks</tt> field.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<p>Additional fields are present for some special-purpose
+builds, and are discussed separately.
+
+<h3><a name="The rcu_head Structure">
+The <tt>rcu_head</tt> Structure</a></h3>
+
+<p>Each <tt>rcu_head</tt> structure represents an RCU callback.
+These structures are normally embedded within RCU-protected data
+structures whose algorithms use asynchronous grace periods.
+In contrast, when using algorithms that block waiting for RCU grace periods,
+RCU users need not provide <tt>rcu_head</tt> structures.
+
+</p><p>The <tt>rcu_head</tt> structure has fields as follows:
+
+<pre>
+ 1 struct rcu_head *next;
+ 2 void (*func)(struct rcu_head *head);
+</pre>
+
+<p>The <tt>->next</tt> field is used
+to link the <tt>rcu_head</tt> structures together in the
+lists within the <tt>rcu_data</tt> structures.
+The <tt>->func</tt> field is a pointer to the function
+to be called when the callback is ready to be invoked, and
+this function is passed a pointer to the <tt>rcu_head</tt>
+structure.
+However, <tt>kfree_rcu()</tt> uses the <tt>->func</tt>
+field to record the offset of the <tt>rcu_head</tt>
+structure within the enclosing RCU-protected data structure.
+
+</p><p>Both of these fields are used internally by RCU.
+From the viewpoint of RCU users, this structure is an
+opaque “cookie”.
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Given that the callback function <tt>->func</tt>
+ is passed a pointer to the <tt>rcu_head</tt> structure,
+ how is that function supposed to find the beginning of the
+ enclosing RCU-protected data structure?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ In actual practice, there is a separate callback function per
+ type of RCU-protected data structure.
+ The callback function can therefore use the <tt>container_of()</tt>
+ macro in the Linux kernel (or other pointer-manipulation facilities
+ in other software environments) to find the beginning of the
+ enclosing structure.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<h3><a name="RCU-Specific Fields in the task_struct Structure">
+RCU-Specific Fields in the <tt>task_struct</tt> Structure</a></h3>
+
+<p>The <tt>CONFIG_PREEMPT_RCU</tt> implementation uses some
+additional fields in the <tt>task_struct</tt> structure:
+
+<pre>
+ 1 #ifdef CONFIG_PREEMPT_RCU
+ 2 int rcu_read_lock_nesting;
+ 3 union rcu_special rcu_read_unlock_special;
+ 4 struct list_head rcu_node_entry;
+ 5 struct rcu_node *rcu_blocked_node;
+ 6 #endif /* #ifdef CONFIG_PREEMPT_RCU */
+ 7 #ifdef CONFIG_TASKS_RCU
+ 8 unsigned long rcu_tasks_nvcsw;
+ 9 bool rcu_tasks_holdout;
+10 struct list_head rcu_tasks_holdout_list;
+11 int rcu_tasks_idle_cpu;
+12 #endif /* #ifdef CONFIG_TASKS_RCU */
+</pre>
+
+<p>The <tt>->rcu_read_lock_nesting</tt> field records the
+nesting level for RCU read-side critical sections, and
+the <tt>->rcu_read_unlock_special</tt> field is a bitmask
+that records special conditions that require <tt>rcu_read_unlock()</tt>
+to do additional work.
+The <tt>->rcu_node_entry</tt> field is used to form lists of
+tasks that have blocked within preemptible-RCU read-side critical
+sections and the <tt>->rcu_blocked_node</tt> field references
+the <tt>rcu_node</tt> structure whose list this task is a member of,
+or <tt>NULL</tt> if it is not blocked within a preemptible-RCU
+read-side critical section.
+
+<p>The <tt>->rcu_tasks_nvcsw</tt> field tracks the number of
+voluntary context switches that this task had undergone at the
+beginning of the current tasks-RCU grace period,
+<tt>->rcu_tasks_holdout</tt> is set if the current tasks-RCU
+grace period is waiting on this task, <tt>->rcu_tasks_holdout_list</tt>
+is a list element enqueuing this task on the holdout list,
+and <tt>->rcu_tasks_idle_cpu</tt> tracks which CPU this
+idle task is running, but only if the task is currently running,
+that is, if the CPU is currently idle.
+
+<h3><a name="Accessor Functions">
+Accessor Functions</a></h3>
+
+<p>The following listing shows the
+<tt>rcu_get_root()</tt>, <tt>rcu_for_each_node_breadth_first</tt>,
+<tt>rcu_for_each_nonleaf_node_breadth_first()</tt>, and
+<tt>rcu_for_each_leaf_node()</tt> function and macros:
+
+<pre>
+ 1 static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
+ 2 {
+ 3 return &rsp->node[0];
+ 4 }
+ 5
+ 6 #define rcu_for_each_node_breadth_first(rsp, rnp) \
+ 7 for ((rnp) = &(rsp)->node[0]; \
+ 8 (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
+ 9
+ 10 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
+ 11 for ((rnp) = &(rsp)->node[0]; \
+ 12 (rnp) < (rsp)->level[NUM_RCU_LVLS - 1]; (rnp)++)
+ 13
+ 14 #define rcu_for_each_leaf_node(rsp, rnp) \
+ 15 for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \
+ 16 (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
+</pre>
+
+<p>The <tt>rcu_get_root()</tt> simply returns a pointer to the
+first element of the specified <tt>rcu_state</tt> structure's
+<tt>->node[]</tt> array, which is the root <tt>rcu_node</tt>
+structure.
+
+</p><p>As noted earlier, the <tt>rcu_for_each_node_breadth_first()</tt>
+macro takes advantage of the layout of the <tt>rcu_node</tt>
+structures in the <tt>rcu_state</tt> structure's
+<tt>->node[]</tt> array, performing a breadth-first traversal by
+simply traversing the array in order.
+The <tt>rcu_for_each_nonleaf_node_breadth_first()</tt> macro operates
+similarly, but traverses only the first part of the array, thus excluding
+the leaf <tt>rcu_node</tt> structures.
+Finally, the <tt>rcu_for_each_leaf_node()</tt> macro traverses only
+the last part of the array, thus traversing only the leaf
+<tt>rcu_node</tt> structures.
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ What do <tt>rcu_for_each_nonleaf_node_breadth_first()</tt> and
+ <tt>rcu_for_each_leaf_node()</tt> do if the <tt>rcu_node</tt> tree
+ contains only a single node?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ In the single-node case,
+ <tt>rcu_for_each_nonleaf_node_breadth_first()</tt> is a no-op
+ and <tt>rcu_for_each_leaf_node()</tt> traverses the single node.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<h3><a name="Summary">
+Summary</a></h3>
+
+So each flavor of RCU is represented by an <tt>rcu_state</tt> structure,
+which contains a combining tree of <tt>rcu_node</tt> and
+<tt>rcu_data</tt> structures.
+Finally, in <tt>CONFIG_NO_HZ_IDLE</tt> kernels, each CPU's dyntick-idle
+state is tracked by an <tt>rcu_dynticks</tt> structure.
+
+If you made it this far, you are well prepared to read the code
+walkthroughs in the other articles in this series.
+
+<h3><a name="Acknowledgments">
+Acknowledgments</a></h3>
+
+I owe thanks to Cyrill Gorcunov, Mathieu Desnoyers, Dhaval Giani, Paul
+Turner, Abhishek Srivastava, Matt Kowalczyk, and Serge Hallyn
+for helping me get this document into a more human-readable state.
+
+<h3><a name="Legal Statement">
+Legal Statement</a></h3>
+
+<p>This work represents the view of the author and does not necessarily
+represent the view of IBM.
+
+</p><p>Linux is a registered trademark of Linus Torvalds.
+
+</p><p>Other company, product, and service names may be trademarks or
+service marks of others.
+
+</body></html>
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- id="tspan3019">Inconsistent Data OK</tspan></text>
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- id="tspan3021">(RCU Works Great!!!)</tspan></text>
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- id="tspan3023">(RCU Works Well)</tspan></text>
- <!-- Text -->
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- style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
- id="tspan3025">Read-Mostly, Need Consistent Data</tspan></text>
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- style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
- id="tspan3027">Read-Write, Need Consistent Data</tspan></text>
- <!-- Text -->
- <text
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- style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
- sodipodi:linespacing="125%">Update-Mostly, Need Consistent Data</text>
- <!-- Text -->
- <text
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- font-style="normal"
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- id="text28"
- sodipodi:linespacing="125%"
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- style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
- id="tspan3029">(RCU Might Be OK...)</tspan></text>
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- <text
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- sodipodi:linespacing="125%">(1) Provide Existence Guarantees For Update-Friendly Mechanisms</text>
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- sodipodi:linespacing="125%">(2) Provide Wait-Free Read-Side Primitives for Real-Time Use)</text>
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- style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
- sodipodi:linespacing="125%">(RCU is Very Unlikely to be the Right Tool For The Job, But it Can:</text>
- </g>
-</svg>
-<!-- DO NOT HAND EDIT. -->
-<!-- Instead, edit Documentation/RCU/Design/Requirements/Requirements.htmlx and run 'sh htmlqqz.sh Documentation/RCU/Design/Requirements/Requirements' -->
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<p>
This is followed by a <a href="#Summary">summary</a>,
-which is in turn followed by the inevitable
-<a href="#Answers to Quick Quizzes">answers to the quick quizzes</a>.
+however, the answers to each quick quiz immediately follows the quiz.
+Select the big white space with your mouse to see the answer.
<h2><a name="Fundamental Requirements">Fundamental Requirements</a></h2>
</blockquote>
cannot happen.
-<p><a name="Quick Quiz 1"><b>Quick Quiz 1</b>:</a>
-Wait a minute!
-You said that updaters can make useful forward progress concurrently
-with readers, but pre-existing readers will block
-<tt>synchronize_rcu()</tt>!!!
-Just who are you trying to fool???
-<br><a href="#qq1answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Wait a minute!
+ You said that updaters can make useful forward progress concurrently
+ with readers, but pre-existing readers will block
+ <tt>synchronize_rcu()</tt>!!!
+ Just who are you trying to fool???
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ First, if updaters do not wish to be blocked by readers, they can use
+ <tt>call_rcu()</tt> or <tt>kfree_rcu()</tt>, which will
+ be discussed later.
+ Second, even when using <tt>synchronize_rcu()</tt>, the other
+ update-side code does run concurrently with readers, whether
+ pre-existing or not.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
This scenario resembles one of the first uses of RCU in
with <tt>recovery()</tt>, but with little or no synchronization
overhead in <tt>do_something_dlm()</tt>.
-<p><a name="Quick Quiz 2"><b>Quick Quiz 2</b>:</a>
-Why is the <tt>synchronize_rcu()</tt> on line 28 needed?
-<br><a href="#qq2answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Why is the <tt>synchronize_rcu()</tt> on line 28 needed?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ Without that extra grace period, memory reordering could result in
+ <tt>do_something_dlm()</tt> executing <tt>do_something()</tt>
+ concurrently with the last bits of <tt>recovery()</tt>.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
In order to avoid fatal problems such as deadlocks,
optimizations, for example, the use of <tt>gp</tt> as a scratch
location immediately preceding the assignment.
-<p><a name="Quick Quiz 3"><b>Quick Quiz 3</b>:</a>
-But <tt>rcu_assign_pointer()</tt> does nothing to prevent the
-two assignments to <tt>p->a</tt> and <tt>p->b</tt>
-from being reordered.
-Can't that also cause problems?
-<br><a href="#qq3answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ But <tt>rcu_assign_pointer()</tt> does nothing to prevent the
+ two assignments to <tt>p->a</tt> and <tt>p->b</tt>
+ from being reordered.
+ Can't that also cause problems?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ No, it cannot.
+ The readers cannot see either of these two fields until
+ the assignment to <tt>gp</tt>, by which time both fields are
+ fully initialized.
+ So reordering the assignments
+ to <tt>p->a</tt> and <tt>p->b</tt> cannot possibly
+ cause any problems.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
It is tempting to assume that the reader need not do anything special
code protected by the corresponding update-side lock.
</ol>
-<p><a name="Quick Quiz 4"><b>Quick Quiz 4</b>:</a>
-Without the <tt>rcu_dereference()</tt> or the
-<tt>rcu_access_pointer()</tt>, what destructive optimizations
-might the compiler make use of?
-<br><a href="#qq4answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Without the <tt>rcu_dereference()</tt> or the
+ <tt>rcu_access_pointer()</tt>, what destructive optimizations
+ might the compiler make use of?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ Let's start with what happens to <tt>do_something_gp()</tt>
+ if it fails to use <tt>rcu_dereference()</tt>.
+ It could reuse a value formerly fetched from this same pointer.
+ It could also fetch the pointer from <tt>gp</tt> in a byte-at-a-time
+ manner, resulting in <i>load tearing</i>, in turn resulting a bytewise
+ mash-up of two distince pointer values.
+ It might even use value-speculation optimizations, where it makes
+ a wrong guess, but by the time it gets around to checking the
+ value, an update has changed the pointer to match the wrong guess.
+ Too bad about any dereferences that returned pre-initialization garbage
+ in the meantime!
+ </font>
+
+ <p><font color="ffffff">
+ For <tt>remove_gp_synchronous()</tt>, as long as all modifications
+ to <tt>gp</tt> are carried out while holding <tt>gp_lock</tt>,
+ the above optimizations are harmless.
+ However,
+ with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt>,
+ <tt>sparse</tt> will complain if you
+ define <tt>gp</tt> with <tt>__rcu</tt> and then
+ access it without using
+ either <tt>rcu_access_pointer()</tt> or <tt>rcu_dereference()</tt>.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
In short, RCU's publish-subscribe guarantee is provided by the combination
<tt>synchronize_rcu()</tt> migrates in the meantime.
</ol>
-<p><a name="Quick Quiz 5"><b>Quick Quiz 5</b>:</a>
-Given that multiple CPUs can start RCU read-side critical sections
-at any time without any ordering whatsoever, how can RCU possibly tell whether
-or not a given RCU read-side critical section starts before a
-given instance of <tt>synchronize_rcu()</tt>?
-<br><a href="#qq5answer">Answer</a>
-
-<p><a name="Quick Quiz 6"><b>Quick Quiz 6</b>:</a>
-The first and second guarantees require unbelievably strict ordering!
-Are all these memory barriers <i> really</i> required?
-<br><a href="#qq6answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Given that multiple CPUs can start RCU read-side critical sections
+ at any time without any ordering whatsoever, how can RCU possibly
+ tell whether or not a given RCU read-side critical section starts
+ before a given instance of <tt>synchronize_rcu()</tt>?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ If RCU cannot tell whether or not a given
+ RCU read-side critical section starts before a
+ given instance of <tt>synchronize_rcu()</tt>,
+ then it must assume that the RCU read-side critical section
+ started first.
+ In other words, a given instance of <tt>synchronize_rcu()</tt>
+ can avoid waiting on a given RCU read-side critical section only
+ if it can prove that <tt>synchronize_rcu()</tt> started first.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ The first and second guarantees require unbelievably strict ordering!
+ Are all these memory barriers <i> really</i> required?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ Yes, they really are required.
+ To see why the first guarantee is required, consider the following
+ sequence of events:
+ </font>
+
+ <ol>
+ <li> <font color="ffffff">
+ CPU 1: <tt>rcu_read_lock()</tt>
+ </font>
+ <li> <font color="ffffff">
+ CPU 1: <tt>q = rcu_dereference(gp);
+ /* Very likely to return p. */</tt>
+ </font>
+ <li> <font color="ffffff">
+ CPU 0: <tt>list_del_rcu(p);</tt>
+ </font>
+ <li> <font color="ffffff">
+ CPU 0: <tt>synchronize_rcu()</tt> starts.
+ </font>
+ <li> <font color="ffffff">
+ CPU 1: <tt>do_something_with(q->a);
+ /* No smp_mb(), so might happen after kfree(). */</tt>
+ </font>
+ <li> <font color="ffffff">
+ CPU 1: <tt>rcu_read_unlock()</tt>
+ </font>
+ <li> <font color="ffffff">
+ CPU 0: <tt>synchronize_rcu()</tt> returns.
+ </font>
+ <li> <font color="ffffff">
+ CPU 0: <tt>kfree(p);</tt>
+ </font>
+ </ol>
+
+ <p><font color="ffffff">
+ Therefore, there absolutely must be a full memory barrier between the
+ end of the RCU read-side critical section and the end of the
+ grace period.
+ </font>
+
+ <p><font color="ffffff">
+ The sequence of events demonstrating the necessity of the second rule
+ is roughly similar:
+ </font>
+
+ <ol>
+ <li> <font color="ffffff">CPU 0: <tt>list_del_rcu(p);</tt>
+ </font>
+ <li> <font color="ffffff">CPU 0: <tt>synchronize_rcu()</tt> starts.
+ </font>
+ <li> <font color="ffffff">CPU 1: <tt>rcu_read_lock()</tt>
+ </font>
+ <li> <font color="ffffff">CPU 1: <tt>q = rcu_dereference(gp);
+ /* Might return p if no memory barrier. */</tt>
+ </font>
+ <li> <font color="ffffff">CPU 0: <tt>synchronize_rcu()</tt> returns.
+ </font>
+ <li> <font color="ffffff">CPU 0: <tt>kfree(p);</tt>
+ </font>
+ <li> <font color="ffffff">
+ CPU 1: <tt>do_something_with(q->a); /* Boom!!! */</tt>
+ </font>
+ <li> <font color="ffffff">CPU 1: <tt>rcu_read_unlock()</tt>
+ </font>
+ </ol>
+
+ <p><font color="ffffff">
+ And similarly, without a memory barrier between the beginning of the
+ grace period and the beginning of the RCU read-side critical section,
+ CPU 1 might end up accessing the freelist.
+ </font>
+
+ <p><font color="ffffff">
+ The “as if” rule of course applies, so that any
+ implementation that acts as if the appropriate memory barriers
+ were in place is a correct implementation.
+ That said, it is much easier to fool yourself into believing
+ that you have adhered to the as-if rule than it is to actually
+ adhere to it!
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ You claim that <tt>rcu_read_lock()</tt> and <tt>rcu_read_unlock()</tt>
+ generate absolutely no code in some kernel builds.
+ This means that the compiler might arbitrarily rearrange consecutive
+ RCU read-side critical sections.
+ Given such rearrangement, if a given RCU read-side critical section
+ is done, how can you be sure that all prior RCU read-side critical
+ sections are done?
+ Won't the compiler rearrangements make that impossible to determine?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ In cases where <tt>rcu_read_lock()</tt> and <tt>rcu_read_unlock()</tt>
+ generate absolutely no code, RCU infers quiescent states only at
+ special locations, for example, within the scheduler.
+ Because calls to <tt>schedule()</tt> had better prevent calling-code
+ accesses to shared variables from being rearranged across the call to
+ <tt>schedule()</tt>, if RCU detects the end of a given RCU read-side
+ critical section, it will necessarily detect the end of all prior
+ RCU read-side critical sections, no matter how aggressively the
+ compiler scrambles the code.
+ </font>
+
+ <p><font color="ffffff">
+ Again, this all assumes that the compiler cannot scramble code across
+ calls to the scheduler, out of interrupt handlers, into the idle loop,
+ into user-mode code, and so on.
+ But if your kernel build allows that sort of scrambling, you have broken
+ far more than just RCU!
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
Note that these memory-barrier requirements do not replace the fundamental
<tt>call_rcu()</tt> and <tt>kfree_rcu()</tt> API members
described later in this document.
-<p><a name="Quick Quiz 7"><b>Quick Quiz 7</b>:</a>
-But how does the upgrade-to-write operation exclude other readers?
-<br><a href="#qq7answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ But how does the upgrade-to-write operation exclude other readers?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ It doesn't, just like normal RCU updates, which also do not exclude
+ RCU readers.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
This guarantee allows lookup code to be shared between read-side
This is by design: Any significant ordering constraints would slow down
these fast-path APIs.
-<p><a name="Quick Quiz 8"><b>Quick Quiz 8</b>:</a>
-Can't the compiler also reorder this code?
-<br><a href="#qq8answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Can't the compiler also reorder this code?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ No, the volatile casts in <tt>READ_ONCE()</tt> and
+ <tt>WRITE_ONCE()</tt> prevent the compiler from reordering in
+ this particular case.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<h3><a name="Readers Do Not Exclude Updaters">Readers Do Not Exclude Updaters</a></h3>
starts, and <tt>synchronize_rcu()</tt> is under no
obligation to wait for these new readers.
-<p><a name="Quick Quiz 9"><b>Quick Quiz 9</b>:</a>
-Suppose that synchronize_rcu() did wait until all readers had completed.
-Would the updater be able to rely on this?
-<br><a href="#qq9answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Suppose that synchronize_rcu() did wait until <i>all</i>
+ readers had completed instead of waiting only on
+ pre-existing readers.
+ For how long would the updater be able to rely on there
+ being no readers?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ For no time at all.
+ Even if <tt>synchronize_rcu()</tt> were to wait until
+ all readers had completed, a new reader might start immediately after
+ <tt>synchronize_rcu()</tt> completed.
+ Therefore, the code following
+ <tt>synchronize_rcu()</tt> can <i>never</i> rely on there being
+ no readers.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<h3><a name="Grace Periods Don't Partition Read-Side Critical Sections">
Grace Periods Don't Partition Read-Side Critical Sections</a></h3>
As a result, an RCU read-side critical section cannot partition a pair
of RCU grace periods.
-<p><a name="Quick Quiz 10"><b>Quick Quiz 10</b>:</a>
-How long a sequence of grace periods, each separated by an RCU read-side
-critical section, would be required to partition the RCU read-side
-critical sections at the beginning and end of the chain?
-<br><a href="#qq10answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ How long a sequence of grace periods, each separated by an RCU
+ read-side critical section, would be required to partition the RCU
+ read-side critical sections at the beginning and end of the chain?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ In theory, an infinite number.
+ In practice, an unknown number that is sensitive to both implementation
+ details and timing considerations.
+ Therefore, even in practice, RCU users must abide by the
+ theoretical rather than the practical answer.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<h3><a name="Disabling Preemption Does Not Block Grace Periods">
Disabling Preemption Does Not Block Grace Periods</a></h3>
<h3><a name="Specialization">Specialization</a></h3>
<p>
-RCU is and always has been intended primarily for read-mostly situations, as
-illustrated by the following figure.
-This means that RCU's read-side primitives are optimized, often at the
+RCU is and always has been intended primarily for read-mostly situations,
+which means that RCU's read-side primitives are optimized, often at the
expense of its update-side primitives.
+Experience thus far is captured by the following list of situations:
-<p><img src="RCUApplicability.svg" alt="RCUApplicability.svg" width="70%"></p>
+<ol>
+<li> Read-mostly data, where stale and inconsistent data is not
+ a problem: RCU works great!
+<li> Read-mostly data, where data must be consistent:
+ RCU works well.
+<li> Read-write data, where data must be consistent:
+ RCU <i>might</i> work OK.
+ Or not.
+<li> Write-mostly data, where data must be consistent:
+ RCU is very unlikely to be the right tool for the job,
+ with the following exceptions, where RCU can provide:
+ <ol type=a>
+ <li> Existence guarantees for update-friendly mechanisms.
+ <li> Wait-free read-side primitives for real-time use.
+ </ol>
+</ol>
<p>
This focus on read-mostly situations means that RCU must interoperate
including spinlocks, sequence locks, atomic operations, reference
counters, and memory barriers.
-<p><a name="Quick Quiz 11"><b>Quick Quiz 11</b>:</a>
-What about sleeping locks?
-<br><a href="#qq11answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ What about sleeping locks?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ These are forbidden within Linux-kernel RCU read-side critical
+ sections because it is not legal to place a quiescent state
+ (in this case, voluntary context switch) within an RCU read-side
+ critical section.
+ However, sleeping locks may be used within userspace RCU read-side
+ critical sections, and also within Linux-kernel sleepable RCU
+ <a href="#Sleepable RCU"><font color="ffffff">(SRCU)</font></a>
+ read-side critical sections.
+ In addition, the -rt patchset turns spinlocks into a
+ sleeping locks so that the corresponding critical sections
+ can be preempted, which also means that these sleeplockified
+ spinlocks (but not other sleeping locks!) may be acquire within
+ -rt-Linux-kernel RCU read-side critical sections.
+ </font>
+
+ <p><font color="ffffff">
+ Note that it <i>is</i> legal for a normal RCU read-side
+ critical section to conditionally acquire a sleeping locks
+ (as in <tt>mutex_trylock()</tt>), but only as long as it does
+ not loop indefinitely attempting to conditionally acquire that
+ sleeping locks.
+ The key point is that things like <tt>mutex_trylock()</tt>
+ either return with the mutex held, or return an error indication if
+ the mutex was not immediately available.
+ Either way, <tt>mutex_trylock()</tt> returns immediately without
+ sleeping.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
It often comes as a surprise that many algorithms do not require a
One of our pair of veternarians might wait 30 seconds before pronouncing
the cat dead, while the other might insist on waiting a full minute.
The two veternarians would then disagree on the state of the cat during
-the final 30 seconds of the minute following the last heartbeat, as
-fancifully illustrated below:
-
-<p><img src="2013-08-is-it-dead.png" alt="2013-08-is-it-dead.png" width="431"></p>
+the final 30 seconds of the minute following the last heartbeat.
<p>
Interestingly enough, this same situation applies to hardware.
<tt>synchronize_rcu_expedited()</tt> would be legal,
including within preempt-disable code, <tt>local_bh_disable()</tt> code,
interrupt-disable code, and interrupt handlers.
-However, even <tt>call_rcu()</tt> is illegal within NMI handlers.
+However, even <tt>call_rcu()</tt> is illegal within NMI handlers
+and from idle and offline CPUs.
The callback function (<tt>remove_gp_cb()</tt> in this case) will be
executed within softirq (software interrupt) environment within the
Linux kernel,
Long-running operations should be relegated to separate threads or
(in the Linux kernel) workqueues.
-<p><a name="Quick Quiz 12"><b>Quick Quiz 12</b>:</a>
-Why does line 19 use <tt>rcu_access_pointer()</tt>?
-After all, <tt>call_rcu()</tt> on line 25 stores into the
-structure, which would interact badly with concurrent insertions.
-Doesn't this mean that <tt>rcu_dereference()</tt> is required?
-<br><a href="#qq12answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Why does line 19 use <tt>rcu_access_pointer()</tt>?
+ After all, <tt>call_rcu()</tt> on line 25 stores into the
+ structure, which would interact badly with concurrent insertions.
+ Doesn't this mean that <tt>rcu_dereference()</tt> is required?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ Presumably the <tt>->gp_lock</tt> acquired on line 18 excludes
+ any changes, including any insertions that <tt>rcu_dereference()</tt>
+ would protect against.
+ Therefore, any insertions will be delayed until after
+ <tt>->gp_lock</tt>
+ is released on line 25, which in turn means that
+ <tt>rcu_access_pointer()</tt> suffices.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
However, all that <tt>remove_gp_cb()</tt> is doing is
so the very few places that needed something like
<tt>synchronize_rcu()</tt> simply open-coded it.
-<p><a name="Quick Quiz 13"><b>Quick Quiz 13</b>:</a>
-Earlier it was claimed that <tt>call_rcu()</tt> and
-<tt>kfree_rcu()</tt> allowed updaters to avoid being blocked
-by readers.
-But how can that be correct, given that the invocation of the callback
-and the freeing of the memory (respectively) must still wait for
-a grace period to elapse?
-<br><a href="#qq13answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ Earlier it was claimed that <tt>call_rcu()</tt> and
+ <tt>kfree_rcu()</tt> allowed updaters to avoid being blocked
+ by readers.
+ But how can that be correct, given that the invocation of the callback
+ and the freeing of the memory (respectively) must still wait for
+ a grace period to elapse?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ We could define things this way, but keep in mind that this sort of
+ definition would say that updates in garbage-collected languages
+ cannot complete until the next time the garbage collector runs,
+ which does not seem at all reasonable.
+ The key point is that in most cases, an updater using either
+ <tt>call_rcu()</tt> or <tt>kfree_rcu()</tt> can proceed to the
+ next update as soon as it has invoked <tt>call_rcu()</tt> or
+ <tt>kfree_rcu()</tt>, without having to wait for a subsequent
+ grace period.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
But what if the updater must wait for the completion of code to be
Therefore, invoking <tt>synchronize_rcu()</tt> during scheduler
initialization can result in deadlock.
-<p><a name="Quick Quiz 14"><b>Quick Quiz 14</b>:</a>
-So what happens with <tt>synchronize_rcu()</tt> during
-scheduler initialization for <tt>CONFIG_PREEMPT=n</tt>
-kernels?
-<br><a href="#qq14answer">Answer</a>
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ So what happens with <tt>synchronize_rcu()</tt> during
+ scheduler initialization for <tt>CONFIG_PREEMPT=n</tt>
+ kernels?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ In <tt>CONFIG_PREEMPT=n</tt> kernel, <tt>synchronize_rcu()</tt>
+ maps directly to <tt>synchronize_sched()</tt>.
+ Therefore, <tt>synchronize_rcu()</tt> works normally throughout
+ boot in <tt>CONFIG_PREEMPT=n</tt> kernels.
+ However, your code must also work in <tt>CONFIG_PREEMPT=y</tt> kernels,
+ so it is still necessary to avoid invoking <tt>synchronize_rcu()</tt>
+ during scheduler initialization.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
<p>
I learned of these boot-time requirements as a result of a series of
This real-time requirement motivated the grace-period kthread, which
also simplified handling of a number of race conditions.
+<p>
+RCU must avoid degrading real-time response for CPU-bound threads, whether
+executing in usermode (which is one use case for
+<tt>CONFIG_NO_HZ_FULL=y</tt>) or in the kernel.
+That said, CPU-bound loops in the kernel must execute
+<tt>cond_resched_rcu_qs()</tt> at least once per few tens of milliseconds
+in order to avoid receiving an IPI from RCU.
+
<p>
Finally, RCU's status as a synchronization primitive means that
any RCU failure can result in arbitrary memory corruption that can be
<li> <a href="#Sched Flavor">Sched Flavor</a>
<li> <a href="#Sleepable RCU">Sleepable RCU</a>
<li> <a href="#Tasks RCU">Tasks RCU</a>
+<li> <a href="#Waiting for Multiple Grace Periods">
+ Waiting for Multiple Grace Periods</a>
</ol>
<h3><a name="Bottom-Half Flavor">Bottom-Half Flavor</a></h3>
<tt>synchronize_rcu_tasks()</tt>, and
<tt>rcu_barrier_tasks()</tt>.
+<h3><a name="Waiting for Multiple Grace Periods">
+Waiting for Multiple Grace Periods</a></h3>
+
+<p>
+Perhaps you have an RCU protected data structure that is accessed from
+RCU read-side critical sections, from softirq handlers, and from
+hardware interrupt handlers.
+That is three flavors of RCU, the normal flavor, the bottom-half flavor,
+and the sched flavor.
+How to wait for a compound grace period?
+
+<p>
+The best approach is usually to “just say no!” and
+insert <tt>rcu_read_lock()</tt> and <tt>rcu_read_unlock()</tt>
+around each RCU read-side critical section, regardless of what
+environment it happens to be in.
+But suppose that some of the RCU read-side critical sections are
+on extremely hot code paths, and that use of <tt>CONFIG_PREEMPT=n</tt>
+is not a viable option, so that <tt>rcu_read_lock()</tt> and
+<tt>rcu_read_unlock()</tt> are not free.
+What then?
+
+<p>
+You <i>could</i> wait on all three grace periods in succession, as follows:
+
+<blockquote>
+<pre>
+ 1 synchronize_rcu();
+ 2 synchronize_rcu_bh();
+ 3 synchronize_sched();
+</pre>
+</blockquote>
+
+<p>
+This works, but triples the update-side latency penalty.
+In cases where this is not acceptable, <tt>synchronize_rcu_mult()</tt>
+may be used to wait on all three flavors of grace period concurrently:
+
+<blockquote>
+<pre>
+ 1 synchronize_rcu_mult(call_rcu, call_rcu_bh, call_rcu_sched);
+</pre>
+</blockquote>
+
+<p>
+But what if it is necessary to also wait on SRCU?
+This can be done as follows:
+
+<blockquote>
+<pre>
+ 1 static void call_my_srcu(struct rcu_head *head,
+ 2 void (*func)(struct rcu_head *head))
+ 3 {
+ 4 call_srcu(&my_srcu, head, func);
+ 5 }
+ 6
+ 7 synchronize_rcu_mult(call_rcu, call_rcu_bh, call_rcu_sched, call_my_srcu);
+</pre>
+</blockquote>
+
+<p>
+If you needed to wait on multiple different flavors of SRCU
+(but why???), you would need to create a wrapper function resembling
+<tt>call_my_srcu()</tt> for each SRCU flavor.
+
+<table>
+<tr><th> </th></tr>
+<tr><th align="left">Quick Quiz:</th></tr>
+<tr><td>
+ But what if I need to wait for multiple RCU flavors, but I also need
+ the grace periods to be expedited?
+</td></tr>
+<tr><th align="left">Answer:</th></tr>
+<tr><td bgcolor="#ffffff"><font color="ffffff">
+ If you are using expedited grace periods, there should be less penalty
+ for waiting on them in succession.
+ But if that is nevertheless a problem, you can use workqueues
+ or multiple kthreads to wait on the various expedited grace
+ periods concurrently.
+</font></td></tr>
+<tr><td> </td></tr>
+</table>
+
+<p>
+Again, it is usually better to adjust the RCU read-side critical sections
+to use a single flavor of RCU, but when this is not feasible, you can use
+<tt>synchronize_rcu_mult()</tt>.
+
<h2><a name="Possible Future Changes">Possible Future Changes</a></h2>
<p>
under the terms of the Creative Commons Attribution-Share Alike 3.0
United States license.
-<h3><a name="Answers to Quick Quizzes">
-Answers to Quick Quizzes</a></h3>
-
-<a name="qq1answer"></a>
-<p><b>Quick Quiz 1</b>:
-Wait a minute!
-You said that updaters can make useful forward progress concurrently
-with readers, but pre-existing readers will block
-<tt>synchronize_rcu()</tt>!!!
-Just who are you trying to fool???
-
-
-</p><p><b>Answer</b>:
-First, if updaters do not wish to be blocked by readers, they can use
-<tt>call_rcu()</tt> or <tt>kfree_rcu()</tt>, which will
-be discussed later.
-Second, even when using <tt>synchronize_rcu()</tt>, the other
-update-side code does run concurrently with readers, whether pre-existing
-or not.
-
-
-</p><p><a href="#Quick%20Quiz%201"><b>Back to Quick Quiz 1</b>.</a>
-
-<a name="qq2answer"></a>
-<p><b>Quick Quiz 2</b>:
-Why is the <tt>synchronize_rcu()</tt> on line 28 needed?
-
-
-</p><p><b>Answer</b>:
-Without that extra grace period, memory reordering could result in
-<tt>do_something_dlm()</tt> executing <tt>do_something()</tt>
-concurrently with the last bits of <tt>recovery()</tt>.
-
-
-</p><p><a href="#Quick%20Quiz%202"><b>Back to Quick Quiz 2</b>.</a>
-
-<a name="qq3answer"></a>
-<p><b>Quick Quiz 3</b>:
-But <tt>rcu_assign_pointer()</tt> does nothing to prevent the
-two assignments to <tt>p->a</tt> and <tt>p->b</tt>
-from being reordered.
-Can't that also cause problems?
-
-
-</p><p><b>Answer</b>:
-No, it cannot.
-The readers cannot see either of these two fields until
-the assignment to <tt>gp</tt>, by which time both fields are
-fully initialized.
-So reordering the assignments
-to <tt>p->a</tt> and <tt>p->b</tt> cannot possibly
-cause any problems.
-
-
-</p><p><a href="#Quick%20Quiz%203"><b>Back to Quick Quiz 3</b>.</a>
-
-<a name="qq4answer"></a>
-<p><b>Quick Quiz 4</b>:
-Without the <tt>rcu_dereference()</tt> or the
-<tt>rcu_access_pointer()</tt>, what destructive optimizations
-might the compiler make use of?
-
-
-</p><p><b>Answer</b>:
-Let's start with what happens to <tt>do_something_gp()</tt>
-if it fails to use <tt>rcu_dereference()</tt>.
-It could reuse a value formerly fetched from this same pointer.
-It could also fetch the pointer from <tt>gp</tt> in a byte-at-a-time
-manner, resulting in <i>load tearing</i>, in turn resulting a bytewise
-mash-up of two distince pointer values.
-It might even use value-speculation optimizations, where it makes a wrong
-guess, but by the time it gets around to checking the value, an update
-has changed the pointer to match the wrong guess.
-Too bad about any dereferences that returned pre-initialization garbage
-in the meantime!
-
-<p>
-For <tt>remove_gp_synchronous()</tt>, as long as all modifications
-to <tt>gp</tt> are carried out while holding <tt>gp_lock</tt>,
-the above optimizations are harmless.
-However,
-with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt>,
-<tt>sparse</tt> will complain if you
-define <tt>gp</tt> with <tt>__rcu</tt> and then
-access it without using
-either <tt>rcu_access_pointer()</tt> or <tt>rcu_dereference()</tt>.
-
-
-</p><p><a href="#Quick%20Quiz%204"><b>Back to Quick Quiz 4</b>.</a>
-
-<a name="qq5answer"></a>
-<p><b>Quick Quiz 5</b>:
-Given that multiple CPUs can start RCU read-side critical sections
-at any time without any ordering whatsoever, how can RCU possibly tell whether
-or not a given RCU read-side critical section starts before a
-given instance of <tt>synchronize_rcu()</tt>?
-
-
-</p><p><b>Answer</b>:
-If RCU cannot tell whether or not a given
-RCU read-side critical section starts before a
-given instance of <tt>synchronize_rcu()</tt>,
-then it must assume that the RCU read-side critical section
-started first.
-In other words, a given instance of <tt>synchronize_rcu()</tt>
-can avoid waiting on a given RCU read-side critical section only
-if it can prove that <tt>synchronize_rcu()</tt> started first.
-
-
-</p><p><a href="#Quick%20Quiz%205"><b>Back to Quick Quiz 5</b>.</a>
-
-<a name="qq6answer"></a>
-<p><b>Quick Quiz 6</b>:
-The first and second guarantees require unbelievably strict ordering!
-Are all these memory barriers <i> really</i> required?
-
-
-</p><p><b>Answer</b>:
-Yes, they really are required.
-To see why the first guarantee is required, consider the following
-sequence of events:
-
-<ol>
-<li> CPU 1: <tt>rcu_read_lock()</tt>
-<li> CPU 1: <tt>q = rcu_dereference(gp);
- /* Very likely to return p. */</tt>
-<li> CPU 0: <tt>list_del_rcu(p);</tt>
-<li> CPU 0: <tt>synchronize_rcu()</tt> starts.
-<li> CPU 1: <tt>do_something_with(q->a);
- /* No smp_mb(), so might happen after kfree(). */</tt>
-<li> CPU 1: <tt>rcu_read_unlock()</tt>
-<li> CPU 0: <tt>synchronize_rcu()</tt> returns.
-<li> CPU 0: <tt>kfree(p);</tt>
-</ol>
-
-<p>
-Therefore, there absolutely must be a full memory barrier between the
-end of the RCU read-side critical section and the end of the
-grace period.
-
-<p>
-The sequence of events demonstrating the necessity of the second rule
-is roughly similar:
-
-<ol>
-<li> CPU 0: <tt>list_del_rcu(p);</tt>
-<li> CPU 0: <tt>synchronize_rcu()</tt> starts.
-<li> CPU 1: <tt>rcu_read_lock()</tt>
-<li> CPU 1: <tt>q = rcu_dereference(gp);
- /* Might return p if no memory barrier. */</tt>
-<li> CPU 0: <tt>synchronize_rcu()</tt> returns.
-<li> CPU 0: <tt>kfree(p);</tt>
-<li> CPU 1: <tt>do_something_with(q->a); /* Boom!!! */</tt>
-<li> CPU 1: <tt>rcu_read_unlock()</tt>
-</ol>
-
-<p>
-And similarly, without a memory barrier between the beginning of the
-grace period and the beginning of the RCU read-side critical section,
-CPU 1 might end up accessing the freelist.
-
-<p>
-The “as if” rule of course applies, so that any implementation
-that acts as if the appropriate memory barriers were in place is a
-correct implementation.
-That said, it is much easier to fool yourself into believing that you have
-adhered to the as-if rule than it is to actually adhere to it!
-
-
-</p><p><a href="#Quick%20Quiz%206"><b>Back to Quick Quiz 6</b>.</a>
-
-<a name="qq7answer"></a>
-<p><b>Quick Quiz 7</b>:
-But how does the upgrade-to-write operation exclude other readers?
-
-
-</p><p><b>Answer</b>:
-It doesn't, just like normal RCU updates, which also do not exclude
-RCU readers.
-
-
-</p><p><a href="#Quick%20Quiz%207"><b>Back to Quick Quiz 7</b>.</a>
-
-<a name="qq8answer"></a>
-<p><b>Quick Quiz 8</b>:
-Can't the compiler also reorder this code?
-
-
-</p><p><b>Answer</b>:
-No, the volatile casts in <tt>READ_ONCE()</tt> and
-<tt>WRITE_ONCE()</tt> prevent the compiler from reordering in
-this particular case.
-
-
-</p><p><a href="#Quick%20Quiz%208"><b>Back to Quick Quiz 8</b>.</a>
-
-<a name="qq9answer"></a>
-<p><b>Quick Quiz 9</b>:
-Suppose that synchronize_rcu() did wait until all readers had completed.
-Would the updater be able to rely on this?
-
-
-</p><p><b>Answer</b>:
-No.
-Even if <tt>synchronize_rcu()</tt> were to wait until
-all readers had completed, a new reader might start immediately after
-<tt>synchronize_rcu()</tt> completed.
-Therefore, the code following
-<tt>synchronize_rcu()</tt> cannot rely on there being no readers
-in any case.
-
-
-</p><p><a href="#Quick%20Quiz%209"><b>Back to Quick Quiz 9</b>.</a>
-
-<a name="qq10answer"></a>
-<p><b>Quick Quiz 10</b>:
-How long a sequence of grace periods, each separated by an RCU read-side
-critical section, would be required to partition the RCU read-side
-critical sections at the beginning and end of the chain?
-
-
-</p><p><b>Answer</b>:
-In theory, an infinite number.
-In practice, an unknown number that is sensitive to both implementation
-details and timing considerations.
-Therefore, even in practice, RCU users must abide by the theoretical rather
-than the practical answer.
-
-
-</p><p><a href="#Quick%20Quiz%2010"><b>Back to Quick Quiz 10</b>.</a>
-
-<a name="qq11answer"></a>
-<p><b>Quick Quiz 11</b>:
-What about sleeping locks?
-
-
-</p><p><b>Answer</b>:
-These are forbidden within Linux-kernel RCU read-side critical sections
-because it is not legal to place a quiescent state (in this case,
-voluntary context switch) within an RCU read-side critical section.
-However, sleeping locks may be used within userspace RCU read-side critical
-sections, and also within Linux-kernel sleepable RCU
-<a href="#Sleepable RCU">(SRCU)</a>
-read-side critical sections.
-In addition, the -rt patchset turns spinlocks into a sleeping locks so
-that the corresponding critical sections can be preempted, which
-also means that these sleeplockified spinlocks (but not other sleeping locks!)
-may be acquire within -rt-Linux-kernel RCU read-side critical sections.
-
-<p>
-Note that it <i>is</i> legal for a normal RCU read-side critical section
-to conditionally acquire a sleeping locks (as in <tt>mutex_trylock()</tt>),
-but only as long as it does not loop indefinitely attempting to
-conditionally acquire that sleeping locks.
-The key point is that things like <tt>mutex_trylock()</tt>
-either return with the mutex held, or return an error indication if
-the mutex was not immediately available.
-Either way, <tt>mutex_trylock()</tt> returns immediately without sleeping.
-
-
-</p><p><a href="#Quick%20Quiz%2011"><b>Back to Quick Quiz 11</b>.</a>
-
-<a name="qq12answer"></a>
-<p><b>Quick Quiz 12</b>:
-Why does line 19 use <tt>rcu_access_pointer()</tt>?
-After all, <tt>call_rcu()</tt> on line 25 stores into the
-structure, which would interact badly with concurrent insertions.
-Doesn't this mean that <tt>rcu_dereference()</tt> is required?
-
-
-</p><p><b>Answer</b>:
-Presumably the <tt>->gp_lock</tt> acquired on line 18 excludes
-any changes, including any insertions that <tt>rcu_dereference()</tt>
-would protect against.
-Therefore, any insertions will be delayed until after <tt>->gp_lock</tt>
-is released on line 25, which in turn means that
-<tt>rcu_access_pointer()</tt> suffices.
-
-
-</p><p><a href="#Quick%20Quiz%2012"><b>Back to Quick Quiz 12</b>.</a>
-
-<a name="qq13answer"></a>
-<p><b>Quick Quiz 13</b>:
-Earlier it was claimed that <tt>call_rcu()</tt> and
-<tt>kfree_rcu()</tt> allowed updaters to avoid being blocked
-by readers.
-But how can that be correct, given that the invocation of the callback
-and the freeing of the memory (respectively) must still wait for
-a grace period to elapse?
-
-
-</p><p><b>Answer</b>:
-We could define things this way, but keep in mind that this sort of
-definition would say that updates in garbage-collected languages
-cannot complete until the next time the garbage collector runs,
-which does not seem at all reasonable.
-The key point is that in most cases, an updater using either
-<tt>call_rcu()</tt> or <tt>kfree_rcu()</tt> can proceed to the
-next update as soon as it has invoked <tt>call_rcu()</tt> or
-<tt>kfree_rcu()</tt>, without having to wait for a subsequent
-grace period.
-
-
-</p><p><a href="#Quick%20Quiz%2013"><b>Back to Quick Quiz 13</b>.</a>
-
-<a name="qq14answer"></a>
-<p><b>Quick Quiz 14</b>:
-So what happens with <tt>synchronize_rcu()</tt> during
-scheduler initialization for <tt>CONFIG_PREEMPT=n</tt>
-kernels?
-
-
-</p><p><b>Answer</b>:
-In <tt>CONFIG_PREEMPT=n</tt> kernel, <tt>synchronize_rcu()</tt>
-maps directly to <tt>synchronize_sched()</tt>.
-Therefore, <tt>synchronize_rcu()</tt> works normally throughout
-boot in <tt>CONFIG_PREEMPT=n</tt> kernels.
-However, your code must also work in <tt>CONFIG_PREEMPT=y</tt> kernels,
-so it is still necessary to avoid invoking <tt>synchronize_rcu()</tt>
-during scheduler initialization.
-
-
-</p><p><a href="#Quick%20Quiz%2014"><b>Back to Quick Quiz 14</b>.</a>
-
-
</body></html>
+++ /dev/null
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
- "http://www.w3.org/TR/html4/loose.dtd">
- <html>
- <head><title>A Tour Through RCU's Requirements [LWN.net]</title>
- <meta HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf-8">
-
-<h1>A Tour Through RCU's Requirements</h1>
-
-<p>Copyright IBM Corporation, 2015</p>
-<p>Author: Paul E. McKenney</p>
-<p><i>The initial version of this document appeared in the
-<a href="https://lwn.net/">LWN</a> articles
-<a href="https://lwn.net/Articles/652156/">here</a>,
-<a href="https://lwn.net/Articles/652677/">here</a>, and
-<a href="https://lwn.net/Articles/653326/">here</a>.</i></p>
-
-<h2>Introduction</h2>
-
-<p>
-Read-copy update (RCU) is a synchronization mechanism that is often
-used as a replacement for reader-writer locking.
-RCU is unusual in that updaters do not block readers,
-which means that RCU's read-side primitives can be exceedingly fast
-and scalable.
-In addition, updaters can make useful forward progress concurrently
-with readers.
-However, all this concurrency between RCU readers and updaters does raise
-the question of exactly what RCU readers are doing, which in turn
-raises the question of exactly what RCU's requirements are.
-
-<p>
-This document therefore summarizes RCU's requirements, and can be thought
-of as an informal, high-level specification for RCU.
-It is important to understand that RCU's specification is primarily
-empirical in nature;
-in fact, I learned about many of these requirements the hard way.
-This situation might cause some consternation, however, not only
-has this learning process been a lot of fun, but it has also been
-a great privilege to work with so many people willing to apply
-technologies in interesting new ways.
-
-<p>
-All that aside, here are the categories of currently known RCU requirements:
-</p>
-
-<ol>
-<li> <a href="#Fundamental Requirements">
- Fundamental Requirements</a>
-<li> <a href="#Fundamental Non-Requirements">Fundamental Non-Requirements</a>
-<li> <a href="#Parallelism Facts of Life">
- Parallelism Facts of Life</a>
-<li> <a href="#Quality-of-Implementation Requirements">
- Quality-of-Implementation Requirements</a>
-<li> <a href="#Linux Kernel Complications">
- Linux Kernel Complications</a>
-<li> <a href="#Software-Engineering Requirements">
- Software-Engineering Requirements</a>
-<li> <a href="#Other RCU Flavors">
- Other RCU Flavors</a>
-<li> <a href="#Possible Future Changes">
- Possible Future Changes</a>
-</ol>
-
-<p>
-This is followed by a <a href="#Summary">summary</a>,
-which is in turn followed by the inevitable
-<a href="#Answers to Quick Quizzes">answers to the quick quizzes</a>.
-
-<h2><a name="Fundamental Requirements">Fundamental Requirements</a></h2>
-
-<p>
-RCU's fundamental requirements are the closest thing RCU has to hard
-mathematical requirements.
-These are:
-
-<ol>
-<li> <a href="#Grace-Period Guarantee">
- Grace-Period Guarantee</a>
-<li> <a href="#Publish-Subscribe Guarantee">
- Publish-Subscribe Guarantee</a>
-<li> <a href="#Memory-Barrier Guarantees">
- Memory-Barrier Guarantees</a>
-<li> <a href="#RCU Primitives Guaranteed to Execute Unconditionally">
- RCU Primitives Guaranteed to Execute Unconditionally</a>
-<li> <a href="#Guaranteed Read-to-Write Upgrade">
- Guaranteed Read-to-Write Upgrade</a>
-</ol>
-
-<h3><a name="Grace-Period Guarantee">Grace-Period Guarantee</a></h3>
-
-<p>
-RCU's grace-period guarantee is unusual in being premeditated:
-Jack Slingwine and I had this guarantee firmly in mind when we started
-work on RCU (then called “rclock”) in the early 1990s.
-That said, the past two decades of experience with RCU have produced
-a much more detailed understanding of this guarantee.
-
-<p>
-RCU's grace-period guarantee allows updaters to wait for the completion
-of all pre-existing RCU read-side critical sections.
-An RCU read-side critical section
-begins with the marker <tt>rcu_read_lock()</tt> and ends with
-the marker <tt>rcu_read_unlock()</tt>.
-These markers may be nested, and RCU treats a nested set as one
-big RCU read-side critical section.
-Production-quality implementations of <tt>rcu_read_lock()</tt> and
-<tt>rcu_read_unlock()</tt> are extremely lightweight, and in
-fact have exactly zero overhead in Linux kernels built for production
-use with <tt>CONFIG_PREEMPT=n</tt>.
-
-<p>
-This guarantee allows ordering to be enforced with extremely low
-overhead to readers, for example:
-
-<blockquote>
-<pre>
- 1 int x, y;
- 2
- 3 void thread0(void)
- 4 {
- 5 rcu_read_lock();
- 6 r1 = READ_ONCE(x);
- 7 r2 = READ_ONCE(y);
- 8 rcu_read_unlock();
- 9 }
-10
-11 void thread1(void)
-12 {
-13 WRITE_ONCE(x, 1);
-14 synchronize_rcu();
-15 WRITE_ONCE(y, 1);
-16 }
-</pre>
-</blockquote>
-
-<p>
-Because the <tt>synchronize_rcu()</tt> on line 14 waits for
-all pre-existing readers, any instance of <tt>thread0()</tt> that
-loads a value of zero from <tt>x</tt> must complete before
-<tt>thread1()</tt> stores to <tt>y</tt>, so that instance must
-also load a value of zero from <tt>y</tt>.
-Similarly, any instance of <tt>thread0()</tt> that loads a value of
-one from <tt>y</tt> must have started after the
-<tt>synchronize_rcu()</tt> started, and must therefore also load
-a value of one from <tt>x</tt>.
-Therefore, the outcome:
-<blockquote>
-<pre>
-(r1 == 0 && r2 == 1)
-</pre>
-</blockquote>
-cannot happen.
-
-<p>@@QQ@@
-Wait a minute!
-You said that updaters can make useful forward progress concurrently
-with readers, but pre-existing readers will block
-<tt>synchronize_rcu()</tt>!!!
-Just who are you trying to fool???
-<p>@@QQA@@
-First, if updaters do not wish to be blocked by readers, they can use
-<tt>call_rcu()</tt> or <tt>kfree_rcu()</tt>, which will
-be discussed later.
-Second, even when using <tt>synchronize_rcu()</tt>, the other
-update-side code does run concurrently with readers, whether pre-existing
-or not.
-<p>@@QQE@@
-
-<p>
-This scenario resembles one of the first uses of RCU in
-<a href="https://en.wikipedia.org/wiki/DYNIX">DYNIX/ptx</a>,
-which managed a distributed lock manager's transition into
-a state suitable for handling recovery from node failure,
-more or less as follows:
-
-<blockquote>
-<pre>
- 1 #define STATE_NORMAL 0
- 2 #define STATE_WANT_RECOVERY 1
- 3 #define STATE_RECOVERING 2
- 4 #define STATE_WANT_NORMAL 3
- 5
- 6 int state = STATE_NORMAL;
- 7
- 8 void do_something_dlm(void)
- 9 {
-10 int state_snap;
-11
-12 rcu_read_lock();
-13 state_snap = READ_ONCE(state);
-14 if (state_snap == STATE_NORMAL)
-15 do_something();
-16 else
-17 do_something_carefully();
-18 rcu_read_unlock();
-19 }
-20
-21 void start_recovery(void)
-22 {
-23 WRITE_ONCE(state, STATE_WANT_RECOVERY);
-24 synchronize_rcu();
-25 WRITE_ONCE(state, STATE_RECOVERING);
-26 recovery();
-27 WRITE_ONCE(state, STATE_WANT_NORMAL);
-28 synchronize_rcu();
-29 WRITE_ONCE(state, STATE_NORMAL);
-30 }
-</pre>
-</blockquote>
-
-<p>
-The RCU read-side critical section in <tt>do_something_dlm()</tt>
-works with the <tt>synchronize_rcu()</tt> in <tt>start_recovery()</tt>
-to guarantee that <tt>do_something()</tt> never runs concurrently
-with <tt>recovery()</tt>, but with little or no synchronization
-overhead in <tt>do_something_dlm()</tt>.
-
-<p>@@QQ@@
-Why is the <tt>synchronize_rcu()</tt> on line 28 needed?
-<p>@@QQA@@
-Without that extra grace period, memory reordering could result in
-<tt>do_something_dlm()</tt> executing <tt>do_something()</tt>
-concurrently with the last bits of <tt>recovery()</tt>.
-<p>@@QQE@@
-
-<p>
-In order to avoid fatal problems such as deadlocks,
-an RCU read-side critical section must not contain calls to
-<tt>synchronize_rcu()</tt>.
-Similarly, an RCU read-side critical section must not
-contain anything that waits, directly or indirectly, on completion of
-an invocation of <tt>synchronize_rcu()</tt>.
-
-<p>
-Although RCU's grace-period guarantee is useful in and of itself, with
-<a href="https://lwn.net/Articles/573497/">quite a few use cases</a>,
-it would be good to be able to use RCU to coordinate read-side
-access to linked data structures.
-For this, the grace-period guarantee is not sufficient, as can
-be seen in function <tt>add_gp_buggy()</tt> below.
-We will look at the reader's code later, but in the meantime, just think of
-the reader as locklessly picking up the <tt>gp</tt> pointer,
-and, if the value loaded is non-<tt>NULL</tt>, locklessly accessing the
-<tt>->a</tt> and <tt>->b</tt> fields.
-
-<blockquote>
-<pre>
- 1 bool add_gp_buggy(int a, int b)
- 2 {
- 3 p = kmalloc(sizeof(*p), GFP_KERNEL);
- 4 if (!p)
- 5 return -ENOMEM;
- 6 spin_lock(&gp_lock);
- 7 if (rcu_access_pointer(gp)) {
- 8 spin_unlock(&gp_lock);
- 9 return false;
-10 }
-11 p->a = a;
-12 p->b = a;
-13 gp = p; /* ORDERING BUG */
-14 spin_unlock(&gp_lock);
-15 return true;
-16 }
-</pre>
-</blockquote>
-
-<p>
-The problem is that both the compiler and weakly ordered CPUs are within
-their rights to reorder this code as follows:
-
-<blockquote>
-<pre>
- 1 bool add_gp_buggy_optimized(int a, int b)
- 2 {
- 3 p = kmalloc(sizeof(*p), GFP_KERNEL);
- 4 if (!p)
- 5 return -ENOMEM;
- 6 spin_lock(&gp_lock);
- 7 if (rcu_access_pointer(gp)) {
- 8 spin_unlock(&gp_lock);
- 9 return false;
-10 }
-<b>11 gp = p; /* ORDERING BUG */
-12 p->a = a;
-13 p->b = a;</b>
-14 spin_unlock(&gp_lock);
-15 return true;
-16 }
-</pre>
-</blockquote>
-
-<p>
-If an RCU reader fetches <tt>gp</tt> just after
-<tt>add_gp_buggy_optimized</tt> executes line 11,
-it will see garbage in the <tt>->a</tt> and <tt>->b</tt>
-fields.
-And this is but one of many ways in which compiler and hardware optimizations
-could cause trouble.
-Therefore, we clearly need some way to prevent the compiler and the CPU from
-reordering in this manner, which brings us to the publish-subscribe
-guarantee discussed in the next section.
-
-<h3><a name="Publish-Subscribe Guarantee">Publish/Subscribe Guarantee</a></h3>
-
-<p>
-RCU's publish-subscribe guarantee allows data to be inserted
-into a linked data structure without disrupting RCU readers.
-The updater uses <tt>rcu_assign_pointer()</tt> to insert the
-new data, and readers use <tt>rcu_dereference()</tt> to
-access data, whether new or old.
-The following shows an example of insertion:
-
-<blockquote>
-<pre>
- 1 bool add_gp(int a, int b)
- 2 {
- 3 p = kmalloc(sizeof(*p), GFP_KERNEL);
- 4 if (!p)
- 5 return -ENOMEM;
- 6 spin_lock(&gp_lock);
- 7 if (rcu_access_pointer(gp)) {
- 8 spin_unlock(&gp_lock);
- 9 return false;
-10 }
-11 p->a = a;
-12 p->b = a;
-13 rcu_assign_pointer(gp, p);
-14 spin_unlock(&gp_lock);
-15 return true;
-16 }
-</pre>
-</blockquote>
-
-<p>
-The <tt>rcu_assign_pointer()</tt> on line 13 is conceptually
-equivalent to a simple assignment statement, but also guarantees
-that its assignment will
-happen after the two assignments in lines 11 and 12,
-similar to the C11 <tt>memory_order_release</tt> store operation.
-It also prevents any number of “interesting” compiler
-optimizations, for example, the use of <tt>gp</tt> as a scratch
-location immediately preceding the assignment.
-
-<p>@@QQ@@
-But <tt>rcu_assign_pointer()</tt> does nothing to prevent the
-two assignments to <tt>p->a</tt> and <tt>p->b</tt>
-from being reordered.
-Can't that also cause problems?
-<p>@@QQA@@
-No, it cannot.
-The readers cannot see either of these two fields until
-the assignment to <tt>gp</tt>, by which time both fields are
-fully initialized.
-So reordering the assignments
-to <tt>p->a</tt> and <tt>p->b</tt> cannot possibly
-cause any problems.
-<p>@@QQE@@
-
-<p>
-It is tempting to assume that the reader need not do anything special
-to control its accesses to the RCU-protected data,
-as shown in <tt>do_something_gp_buggy()</tt> below:
-
-<blockquote>
-<pre>
- 1 bool do_something_gp_buggy(void)
- 2 {
- 3 rcu_read_lock();
- 4 p = gp; /* OPTIMIZATIONS GALORE!!! */
- 5 if (p) {
- 6 do_something(p->a, p->b);
- 7 rcu_read_unlock();
- 8 return true;
- 9 }
-10 rcu_read_unlock();
-11 return false;
-12 }
-</pre>
-</blockquote>
-
-<p>
-However, this temptation must be resisted because there are a
-surprisingly large number of ways that the compiler
-(to say nothing of
-<a href="https://h71000.www7.hp.com/wizard/wiz_2637.html">DEC Alpha CPUs</a>)
-can trip this code up.
-For but one example, if the compiler were short of registers, it
-might choose to refetch from <tt>gp</tt> rather than keeping
-a separate copy in <tt>p</tt> as follows:
-
-<blockquote>
-<pre>
- 1 bool do_something_gp_buggy_optimized(void)
- 2 {
- 3 rcu_read_lock();
- 4 if (gp) { /* OPTIMIZATIONS GALORE!!! */
-<b> 5 do_something(gp->a, gp->b);</b>
- 6 rcu_read_unlock();
- 7 return true;
- 8 }
- 9 rcu_read_unlock();
-10 return false;
-11 }
-</pre>
-</blockquote>
-
-<p>
-If this function ran concurrently with a series of updates that
-replaced the current structure with a new one,
-the fetches of <tt>gp->a</tt>
-and <tt>gp->b</tt> might well come from two different structures,
-which could cause serious confusion.
-To prevent this (and much else besides), <tt>do_something_gp()</tt> uses
-<tt>rcu_dereference()</tt> to fetch from <tt>gp</tt>:
-
-<blockquote>
-<pre>
- 1 bool do_something_gp(void)
- 2 {
- 3 rcu_read_lock();
- 4 p = rcu_dereference(gp);
- 5 if (p) {
- 6 do_something(p->a, p->b);
- 7 rcu_read_unlock();
- 8 return true;
- 9 }
-10 rcu_read_unlock();
-11 return false;
-12 }
-</pre>
-</blockquote>
-
-<p>
-The <tt>rcu_dereference()</tt> uses volatile casts and (for DEC Alpha)
-memory barriers in the Linux kernel.
-Should a
-<a href="http://www.rdrop.com/users/paulmck/RCU/consume.2015.07.13a.pdf">high-quality implementation of C11 <tt>memory_order_consume</tt> [PDF]</a>
-ever appear, then <tt>rcu_dereference()</tt> could be implemented
-as a <tt>memory_order_consume</tt> load.
-Regardless of the exact implementation, a pointer fetched by
-<tt>rcu_dereference()</tt> may not be used outside of the
-outermost RCU read-side critical section containing that
-<tt>rcu_dereference()</tt>, unless protection of
-the corresponding data element has been passed from RCU to some
-other synchronization mechanism, most commonly locking or
-<a href="https://www.kernel.org/doc/Documentation/RCU/rcuref.txt">reference counting</a>.
-
-<p>
-In short, updaters use <tt>rcu_assign_pointer()</tt> and readers
-use <tt>rcu_dereference()</tt>, and these two RCU API elements
-work together to ensure that readers have a consistent view of
-newly added data elements.
-
-<p>
-Of course, it is also necessary to remove elements from RCU-protected
-data structures, for example, using the following process:
-
-<ol>
-<li> Remove the data element from the enclosing structure.
-<li> Wait for all pre-existing RCU read-side critical sections
- to complete (because only pre-existing readers can possibly have
- a reference to the newly removed data element).
-<li> At this point, only the updater has a reference to the
- newly removed data element, so it can safely reclaim
- the data element, for example, by passing it to <tt>kfree()</tt>.
-</ol>
-
-This process is implemented by <tt>remove_gp_synchronous()</tt>:
-
-<blockquote>
-<pre>
- 1 bool remove_gp_synchronous(void)
- 2 {
- 3 struct foo *p;
- 4
- 5 spin_lock(&gp_lock);
- 6 p = rcu_access_pointer(gp);
- 7 if (!p) {
- 8 spin_unlock(&gp_lock);
- 9 return false;
-10 }
-11 rcu_assign_pointer(gp, NULL);
-12 spin_unlock(&gp_lock);
-13 synchronize_rcu();
-14 kfree(p);
-15 return true;
-16 }
-</pre>
-</blockquote>
-
-<p>
-This function is straightforward, with line 13 waiting for a grace
-period before line 14 frees the old data element.
-This waiting ensures that readers will reach line 7 of
-<tt>do_something_gp()</tt> before the data element referenced by
-<tt>p</tt> is freed.
-The <tt>rcu_access_pointer()</tt> on line 6 is similar to
-<tt>rcu_dereference()</tt>, except that:
-
-<ol>
-<li> The value returned by <tt>rcu_access_pointer()</tt>
- cannot be dereferenced.
- If you want to access the value pointed to as well as
- the pointer itself, use <tt>rcu_dereference()</tt>
- instead of <tt>rcu_access_pointer()</tt>.
-<li> The call to <tt>rcu_access_pointer()</tt> need not be
- protected.
- In contrast, <tt>rcu_dereference()</tt> must either be
- within an RCU read-side critical section or in a code
- segment where the pointer cannot change, for example, in
- code protected by the corresponding update-side lock.
-</ol>
-
-<p>@@QQ@@
-Without the <tt>rcu_dereference()</tt> or the
-<tt>rcu_access_pointer()</tt>, what destructive optimizations
-might the compiler make use of?
-<p>@@QQA@@
-Let's start with what happens to <tt>do_something_gp()</tt>
-if it fails to use <tt>rcu_dereference()</tt>.
-It could reuse a value formerly fetched from this same pointer.
-It could also fetch the pointer from <tt>gp</tt> in a byte-at-a-time
-manner, resulting in <i>load tearing</i>, in turn resulting a bytewise
-mash-up of two distince pointer values.
-It might even use value-speculation optimizations, where it makes a wrong
-guess, but by the time it gets around to checking the value, an update
-has changed the pointer to match the wrong guess.
-Too bad about any dereferences that returned pre-initialization garbage
-in the meantime!
-
-<p>
-For <tt>remove_gp_synchronous()</tt>, as long as all modifications
-to <tt>gp</tt> are carried out while holding <tt>gp_lock</tt>,
-the above optimizations are harmless.
-However,
-with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt>,
-<tt>sparse</tt> will complain if you
-define <tt>gp</tt> with <tt>__rcu</tt> and then
-access it without using
-either <tt>rcu_access_pointer()</tt> or <tt>rcu_dereference()</tt>.
-<p>@@QQE@@
-
-<p>
-In short, RCU's publish-subscribe guarantee is provided by the combination
-of <tt>rcu_assign_pointer()</tt> and <tt>rcu_dereference()</tt>.
-This guarantee allows data elements to be safely added to RCU-protected
-linked data structures without disrupting RCU readers.
-This guarantee can be used in combination with the grace-period
-guarantee to also allow data elements to be removed from RCU-protected
-linked data structures, again without disrupting RCU readers.
-
-<p>
-This guarantee was only partially premeditated.
-DYNIX/ptx used an explicit memory barrier for publication, but had nothing
-resembling <tt>rcu_dereference()</tt> for subscription, nor did it
-have anything resembling the <tt>smp_read_barrier_depends()</tt>
-that was later subsumed into <tt>rcu_dereference()</tt>.
-The need for these operations made itself known quite suddenly at a
-late-1990s meeting with the DEC Alpha architects, back in the days when
-DEC was still a free-standing company.
-It took the Alpha architects a good hour to convince me that any sort
-of barrier would ever be needed, and it then took me a good <i>two</i> hours
-to convince them that their documentation did not make this point clear.
-More recent work with the C and C++ standards committees have provided
-much education on tricks and traps from the compiler.
-In short, compilers were much less tricky in the early 1990s, but in
-2015, don't even think about omitting <tt>rcu_dereference()</tt>!
-
-<h3><a name="Memory-Barrier Guarantees">Memory-Barrier Guarantees</a></h3>
-
-<p>
-The previous section's simple linked-data-structure scenario clearly
-demonstrates the need for RCU's stringent memory-ordering guarantees on
-systems with more than one CPU:
-
-<ol>
-<li> Each CPU that has an RCU read-side critical section that
- begins before <tt>synchronize_rcu()</tt> starts is
- guaranteed to execute a full memory barrier between the time
- that the RCU read-side critical section ends and the time that
- <tt>synchronize_rcu()</tt> returns.
- Without this guarantee, a pre-existing RCU read-side critical section
- might hold a reference to the newly removed <tt>struct foo</tt>
- after the <tt>kfree()</tt> on line 14 of
- <tt>remove_gp_synchronous()</tt>.
-<li> Each CPU that has an RCU read-side critical section that ends
- after <tt>synchronize_rcu()</tt> returns is guaranteed
- to execute a full memory barrier between the time that
- <tt>synchronize_rcu()</tt> begins and the time that the RCU
- read-side critical section begins.
- Without this guarantee, a later RCU read-side critical section
- running after the <tt>kfree()</tt> on line 14 of
- <tt>remove_gp_synchronous()</tt> might
- later run <tt>do_something_gp()</tt> and find the
- newly deleted <tt>struct foo</tt>.
-<li> If the task invoking <tt>synchronize_rcu()</tt> remains
- on a given CPU, then that CPU is guaranteed to execute a full
- memory barrier sometime during the execution of
- <tt>synchronize_rcu()</tt>.
- This guarantee ensures that the <tt>kfree()</tt> on
- line 14 of <tt>remove_gp_synchronous()</tt> really does
- execute after the removal on line 11.
-<li> If the task invoking <tt>synchronize_rcu()</tt> migrates
- among a group of CPUs during that invocation, then each of the
- CPUs in that group is guaranteed to execute a full memory barrier
- sometime during the execution of <tt>synchronize_rcu()</tt>.
- This guarantee also ensures that the <tt>kfree()</tt> on
- line 14 of <tt>remove_gp_synchronous()</tt> really does
- execute after the removal on
- line 11, but also in the case where the thread executing the
- <tt>synchronize_rcu()</tt> migrates in the meantime.
-</ol>
-
-<p>@@QQ@@
-Given that multiple CPUs can start RCU read-side critical sections
-at any time without any ordering whatsoever, how can RCU possibly tell whether
-or not a given RCU read-side critical section starts before a
-given instance of <tt>synchronize_rcu()</tt>?
-<p>@@QQA@@
-If RCU cannot tell whether or not a given
-RCU read-side critical section starts before a
-given instance of <tt>synchronize_rcu()</tt>,
-then it must assume that the RCU read-side critical section
-started first.
-In other words, a given instance of <tt>synchronize_rcu()</tt>
-can avoid waiting on a given RCU read-side critical section only
-if it can prove that <tt>synchronize_rcu()</tt> started first.
-<p>@@QQE@@
-
-<p>@@QQ@@
-The first and second guarantees require unbelievably strict ordering!
-Are all these memory barriers <i> really</i> required?
-<p>@@QQA@@
-Yes, they really are required.
-To see why the first guarantee is required, consider the following
-sequence of events:
-
-<ol>
-<li> CPU 1: <tt>rcu_read_lock()</tt>
-<li> CPU 1: <tt>q = rcu_dereference(gp);
- /* Very likely to return p. */</tt>
-<li> CPU 0: <tt>list_del_rcu(p);</tt>
-<li> CPU 0: <tt>synchronize_rcu()</tt> starts.
-<li> CPU 1: <tt>do_something_with(q->a);
- /* No smp_mb(), so might happen after kfree(). */</tt>
-<li> CPU 1: <tt>rcu_read_unlock()</tt>
-<li> CPU 0: <tt>synchronize_rcu()</tt> returns.
-<li> CPU 0: <tt>kfree(p);</tt>
-</ol>
-
-<p>
-Therefore, there absolutely must be a full memory barrier between the
-end of the RCU read-side critical section and the end of the
-grace period.
-
-<p>
-The sequence of events demonstrating the necessity of the second rule
-is roughly similar:
-
-<ol>
-<li> CPU 0: <tt>list_del_rcu(p);</tt>
-<li> CPU 0: <tt>synchronize_rcu()</tt> starts.
-<li> CPU 1: <tt>rcu_read_lock()</tt>
-<li> CPU 1: <tt>q = rcu_dereference(gp);
- /* Might return p if no memory barrier. */</tt>
-<li> CPU 0: <tt>synchronize_rcu()</tt> returns.
-<li> CPU 0: <tt>kfree(p);</tt>
-<li> CPU 1: <tt>do_something_with(q->a); /* Boom!!! */</tt>
-<li> CPU 1: <tt>rcu_read_unlock()</tt>
-</ol>
-
-<p>
-And similarly, without a memory barrier between the beginning of the
-grace period and the beginning of the RCU read-side critical section,
-CPU 1 might end up accessing the freelist.
-
-<p>
-The “as if” rule of course applies, so that any implementation
-that acts as if the appropriate memory barriers were in place is a
-correct implementation.
-That said, it is much easier to fool yourself into believing that you have
-adhered to the as-if rule than it is to actually adhere to it!
-<p>@@QQE@@
-
-<p>
-Note that these memory-barrier requirements do not replace the fundamental
-RCU requirement that a grace period wait for all pre-existing readers.
-On the contrary, the memory barriers called out in this section must operate in
-such a way as to <i>enforce</i> this fundamental requirement.
-Of course, different implementations enforce this requirement in different
-ways, but enforce it they must.
-
-<h3><a name="RCU Primitives Guaranteed to Execute Unconditionally">RCU Primitives Guaranteed to Execute Unconditionally</a></h3>
-
-<p>
-The common-case RCU primitives are unconditional.
-They are invoked, they do their job, and they return, with no possibility
-of error, and no need to retry.
-This is a key RCU design philosophy.
-
-<p>
-However, this philosophy is pragmatic rather than pigheaded.
-If someone comes up with a good justification for a particular conditional
-RCU primitive, it might well be implemented and added.
-After all, this guarantee was reverse-engineered, not premeditated.
-The unconditional nature of the RCU primitives was initially an
-accident of implementation, and later experience with synchronization
-primitives with conditional primitives caused me to elevate this
-accident to a guarantee.
-Therefore, the justification for adding a conditional primitive to
-RCU would need to be based on detailed and compelling use cases.
-
-<h3><a name="Guaranteed Read-to-Write Upgrade">Guaranteed Read-to-Write Upgrade</a></h3>
-
-<p>
-As far as RCU is concerned, it is always possible to carry out an
-update within an RCU read-side critical section.
-For example, that RCU read-side critical section might search for
-a given data element, and then might acquire the update-side
-spinlock in order to update that element, all while remaining
-in that RCU read-side critical section.
-Of course, it is necessary to exit the RCU read-side critical section
-before invoking <tt>synchronize_rcu()</tt>, however, this
-inconvenience can be avoided through use of the
-<tt>call_rcu()</tt> and <tt>kfree_rcu()</tt> API members
-described later in this document.
-
-<p>@@QQ@@
-But how does the upgrade-to-write operation exclude other readers?
-<p>@@QQA@@
-It doesn't, just like normal RCU updates, which also do not exclude
-RCU readers.
-<p>@@QQE@@
-
-<p>
-This guarantee allows lookup code to be shared between read-side
-and update-side code, and was premeditated, appearing in the earliest
-DYNIX/ptx RCU documentation.
-
-<h2><a name="Fundamental Non-Requirements">Fundamental Non-Requirements</a></h2>
-
-<p>
-RCU provides extremely lightweight readers, and its read-side guarantees,
-though quite useful, are correspondingly lightweight.
-It is therefore all too easy to assume that RCU is guaranteeing more
-than it really is.
-Of course, the list of things that RCU does not guarantee is infinitely
-long, however, the following sections list a few non-guarantees that
-have caused confusion.
-Except where otherwise noted, these non-guarantees were premeditated.
-
-<ol>
-<li> <a href="#Readers Impose Minimal Ordering">
- Readers Impose Minimal Ordering</a>
-<li> <a href="#Readers Do Not Exclude Updaters">
- Readers Do Not Exclude Updaters</a>
-<li> <a href="#Updaters Only Wait For Old Readers">
- Updaters Only Wait For Old Readers</a>
-<li> <a href="#Grace Periods Don't Partition Read-Side Critical Sections">
- Grace Periods Don't Partition Read-Side Critical Sections</a>
-<li> <a href="#Read-Side Critical Sections Don't Partition Grace Periods">
- Read-Side Critical Sections Don't Partition Grace Periods</a>
-<li> <a href="#Disabling Preemption Does Not Block Grace Periods">
- Disabling Preemption Does Not Block Grace Periods</a>
-</ol>
-
-<h3><a name="Readers Impose Minimal Ordering">Readers Impose Minimal Ordering</a></h3>
-
-<p>
-Reader-side markers such as <tt>rcu_read_lock()</tt> and
-<tt>rcu_read_unlock()</tt> provide absolutely no ordering guarantees
-except through their interaction with the grace-period APIs such as
-<tt>synchronize_rcu()</tt>.
-To see this, consider the following pair of threads:
-
-<blockquote>
-<pre>
- 1 void thread0(void)
- 2 {
- 3 rcu_read_lock();
- 4 WRITE_ONCE(x, 1);
- 5 rcu_read_unlock();
- 6 rcu_read_lock();
- 7 WRITE_ONCE(y, 1);
- 8 rcu_read_unlock();
- 9 }
-10
-11 void thread1(void)
-12 {
-13 rcu_read_lock();
-14 r1 = READ_ONCE(y);
-15 rcu_read_unlock();
-16 rcu_read_lock();
-17 r2 = READ_ONCE(x);
-18 rcu_read_unlock();
-19 }
-</pre>
-</blockquote>
-
-<p>
-After <tt>thread0()</tt> and <tt>thread1()</tt> execute
-concurrently, it is quite possible to have
-
-<blockquote>
-<pre>
-(r1 == 1 && r2 == 0)
-</pre>
-</blockquote>
-
-(that is, <tt>y</tt> appears to have been assigned before <tt>x</tt>),
-which would not be possible if <tt>rcu_read_lock()</tt> and
-<tt>rcu_read_unlock()</tt> had much in the way of ordering
-properties.
-But they do not, so the CPU is within its rights
-to do significant reordering.
-This is by design: Any significant ordering constraints would slow down
-these fast-path APIs.
-
-<p>@@QQ@@
-Can't the compiler also reorder this code?
-<p>@@QQA@@
-No, the volatile casts in <tt>READ_ONCE()</tt> and
-<tt>WRITE_ONCE()</tt> prevent the compiler from reordering in
-this particular case.
-<p>@@QQE@@
-
-<h3><a name="Readers Do Not Exclude Updaters">Readers Do Not Exclude Updaters</a></h3>
-
-<p>
-Neither <tt>rcu_read_lock()</tt> nor <tt>rcu_read_unlock()</tt>
-exclude updates.
-All they do is to prevent grace periods from ending.
-The following example illustrates this:
-
-<blockquote>
-<pre>
- 1 void thread0(void)
- 2 {
- 3 rcu_read_lock();
- 4 r1 = READ_ONCE(y);
- 5 if (r1) {
- 6 do_something_with_nonzero_x();
- 7 r2 = READ_ONCE(x);
- 8 WARN_ON(!r2); /* BUG!!! */
- 9 }
-10 rcu_read_unlock();
-11 }
-12
-13 void thread1(void)
-14 {
-15 spin_lock(&my_lock);
-16 WRITE_ONCE(x, 1);
-17 WRITE_ONCE(y, 1);
-18 spin_unlock(&my_lock);
-19 }
-</pre>
-</blockquote>
-
-<p>
-If the <tt>thread0()</tt> function's <tt>rcu_read_lock()</tt>
-excluded the <tt>thread1()</tt> function's update,
-the <tt>WARN_ON()</tt> could never fire.
-But the fact is that <tt>rcu_read_lock()</tt> does not exclude
-much of anything aside from subsequent grace periods, of which
-<tt>thread1()</tt> has none, so the
-<tt>WARN_ON()</tt> can and does fire.
-
-<h3><a name="Updaters Only Wait For Old Readers">Updaters Only Wait For Old Readers</a></h3>
-
-<p>
-It might be tempting to assume that after <tt>synchronize_rcu()</tt>
-completes, there are no readers executing.
-This temptation must be avoided because
-new readers can start immediately after <tt>synchronize_rcu()</tt>
-starts, and <tt>synchronize_rcu()</tt> is under no
-obligation to wait for these new readers.
-
-<p>@@QQ@@
-Suppose that synchronize_rcu() did wait until all readers had completed.
-Would the updater be able to rely on this?
-<p>@@QQA@@
-No.
-Even if <tt>synchronize_rcu()</tt> were to wait until
-all readers had completed, a new reader might start immediately after
-<tt>synchronize_rcu()</tt> completed.
-Therefore, the code following
-<tt>synchronize_rcu()</tt> cannot rely on there being no readers
-in any case.
-<p>@@QQE@@
-
-<h3><a name="Grace Periods Don't Partition Read-Side Critical Sections">
-Grace Periods Don't Partition Read-Side Critical Sections</a></h3>
-
-<p>
-It is tempting to assume that if any part of one RCU read-side critical
-section precedes a given grace period, and if any part of another RCU
-read-side critical section follows that same grace period, then all of
-the first RCU read-side critical section must precede all of the second.
-However, this just isn't the case: A single grace period does not
-partition the set of RCU read-side critical sections.
-An example of this situation can be illustrated as follows, where
-<tt>x</tt>, <tt>y</tt>, and <tt>z</tt> are initially all zero:
-
-<blockquote>
-<pre>
- 1 void thread0(void)
- 2 {
- 3 rcu_read_lock();
- 4 WRITE_ONCE(a, 1);
- 5 WRITE_ONCE(b, 1);
- 6 rcu_read_unlock();
- 7 }
- 8
- 9 void thread1(void)
-10 {
-11 r1 = READ_ONCE(a);
-12 synchronize_rcu();
-13 WRITE_ONCE(c, 1);
-14 }
-15
-16 void thread2(void)
-17 {
-18 rcu_read_lock();
-19 r2 = READ_ONCE(b);
-20 r3 = READ_ONCE(c);
-21 rcu_read_unlock();
-22 }
-</pre>
-</blockquote>
-
-<p>
-It turns out that the outcome:
-
-<blockquote>
-<pre>
-(r1 == 1 && r2 == 0 && r3 == 1)
-</pre>
-</blockquote>
-
-is entirely possible.
-The following figure show how this can happen, with each circled
-<tt>QS</tt> indicating the point at which RCU recorded a
-<i>quiescent state</i> for each thread, that is, a state in which
-RCU knows that the thread cannot be in the midst of an RCU read-side
-critical section that started before the current grace period:
-
-<p><img src="GPpartitionReaders1.svg" alt="GPpartitionReaders1.svg" width="60%"></p>
-
-<p>
-If it is necessary to partition RCU read-side critical sections in this
-manner, it is necessary to use two grace periods, where the first
-grace period is known to end before the second grace period starts:
-
-<blockquote>
-<pre>
- 1 void thread0(void)
- 2 {
- 3 rcu_read_lock();
- 4 WRITE_ONCE(a, 1);
- 5 WRITE_ONCE(b, 1);
- 6 rcu_read_unlock();
- 7 }
- 8
- 9 void thread1(void)
-10 {
-11 r1 = READ_ONCE(a);
-12 synchronize_rcu();
-13 WRITE_ONCE(c, 1);
-14 }
-15
-16 void thread2(void)
-17 {
-18 r2 = READ_ONCE(c);
-19 synchronize_rcu();
-20 WRITE_ONCE(d, 1);
-21 }
-22
-23 void thread3(void)
-24 {
-25 rcu_read_lock();
-26 r3 = READ_ONCE(b);
-27 r4 = READ_ONCE(d);
-28 rcu_read_unlock();
-29 }
-</pre>
-</blockquote>
-
-<p>
-Here, if <tt>(r1 == 1)</tt>, then
-<tt>thread0()</tt>'s write to <tt>b</tt> must happen
-before the end of <tt>thread1()</tt>'s grace period.
-If in addition <tt>(r4 == 1)</tt>, then
-<tt>thread3()</tt>'s read from <tt>b</tt> must happen
-after the beginning of <tt>thread2()</tt>'s grace period.
-If it is also the case that <tt>(r2 == 1)</tt>, then the
-end of <tt>thread1()</tt>'s grace period must precede the
-beginning of <tt>thread2()</tt>'s grace period.
-This mean that the two RCU read-side critical sections cannot overlap,
-guaranteeing that <tt>(r3 == 1)</tt>.
-As a result, the outcome:
-
-<blockquote>
-<pre>
-(r1 == 1 && r2 == 1 && r3 == 0 && r4 == 1)
-</pre>
-</blockquote>
-
-cannot happen.
-
-<p>
-This non-requirement was also non-premeditated, but became apparent
-when studying RCU's interaction with memory ordering.
-
-<h3><a name="Read-Side Critical Sections Don't Partition Grace Periods">
-Read-Side Critical Sections Don't Partition Grace Periods</a></h3>
-
-<p>
-It is also tempting to assume that if an RCU read-side critical section
-happens between a pair of grace periods, then those grace periods cannot
-overlap.
-However, this temptation leads nowhere good, as can be illustrated by
-the following, with all variables initially zero:
-
-<blockquote>
-<pre>
- 1 void thread0(void)
- 2 {
- 3 rcu_read_lock();
- 4 WRITE_ONCE(a, 1);
- 5 WRITE_ONCE(b, 1);
- 6 rcu_read_unlock();
- 7 }
- 8
- 9 void thread1(void)
-10 {
-11 r1 = READ_ONCE(a);
-12 synchronize_rcu();
-13 WRITE_ONCE(c, 1);
-14 }
-15
-16 void thread2(void)
-17 {
-18 rcu_read_lock();
-19 WRITE_ONCE(d, 1);
-20 r2 = READ_ONCE(c);
-21 rcu_read_unlock();
-22 }
-23
-24 void thread3(void)
-25 {
-26 r3 = READ_ONCE(d);
-27 synchronize_rcu();
-28 WRITE_ONCE(e, 1);
-29 }
-30
-31 void thread4(void)
-32 {
-33 rcu_read_lock();
-34 r4 = READ_ONCE(b);
-35 r5 = READ_ONCE(e);
-36 rcu_read_unlock();
-37 }
-</pre>
-</blockquote>
-
-<p>
-In this case, the outcome:
-
-<blockquote>
-<pre>
-(r1 == 1 && r2 == 1 && r3 == 1 && r4 == 0 && r5 == 1)
-</pre>
-</blockquote>
-
-is entirely possible, as illustrated below:
-
-<p><img src="ReadersPartitionGP1.svg" alt="ReadersPartitionGP1.svg" width="100%"></p>
-
-<p>
-Again, an RCU read-side critical section can overlap almost all of a
-given grace period, just so long as it does not overlap the entire
-grace period.
-As a result, an RCU read-side critical section cannot partition a pair
-of RCU grace periods.
-
-<p>@@QQ@@
-How long a sequence of grace periods, each separated by an RCU read-side
-critical section, would be required to partition the RCU read-side
-critical sections at the beginning and end of the chain?
-<p>@@QQA@@
-In theory, an infinite number.
-In practice, an unknown number that is sensitive to both implementation
-details and timing considerations.
-Therefore, even in practice, RCU users must abide by the theoretical rather
-than the practical answer.
-<p>@@QQE@@
-
-<h3><a name="Disabling Preemption Does Not Block Grace Periods">
-Disabling Preemption Does Not Block Grace Periods</a></h3>
-
-<p>
-There was a time when disabling preemption on any given CPU would block
-subsequent grace periods.
-However, this was an accident of implementation and is not a requirement.
-And in the current Linux-kernel implementation, disabling preemption
-on a given CPU in fact does not block grace periods, as Oleg Nesterov
-<a href="https://lkml.kernel.org/g/20150614193825.GA19582@redhat.com">demonstrated</a>.
-
-<p>
-If you need a preempt-disable region to block grace periods, you need to add
-<tt>rcu_read_lock()</tt> and <tt>rcu_read_unlock()</tt>, for example
-as follows:
-
-<blockquote>
-<pre>
- 1 preempt_disable();
- 2 rcu_read_lock();
- 3 do_something();
- 4 rcu_read_unlock();
- 5 preempt_enable();
- 6
- 7 /* Spinlocks implicitly disable preemption. */
- 8 spin_lock(&mylock);
- 9 rcu_read_lock();
-10 do_something();
-11 rcu_read_unlock();
-12 spin_unlock(&mylock);
-</pre>
-</blockquote>
-
-<p>
-In theory, you could enter the RCU read-side critical section first,
-but it is more efficient to keep the entire RCU read-side critical
-section contained in the preempt-disable region as shown above.
-Of course, RCU read-side critical sections that extend outside of
-preempt-disable regions will work correctly, but such critical sections
-can be preempted, which forces <tt>rcu_read_unlock()</tt> to do
-more work.
-And no, this is <i>not</i> an invitation to enclose all of your RCU
-read-side critical sections within preempt-disable regions, because
-doing so would degrade real-time response.
-
-<p>
-This non-requirement appeared with preemptible RCU.
-If you need a grace period that waits on non-preemptible code regions, use
-<a href="#Sched Flavor">RCU-sched</a>.
-
-<h2><a name="Parallelism Facts of Life">Parallelism Facts of Life</a></h2>
-
-<p>
-These parallelism facts of life are by no means specific to RCU, but
-the RCU implementation must abide by them.
-They therefore bear repeating:
-
-<ol>
-<li> Any CPU or task may be delayed at any time,
- and any attempts to avoid these delays by disabling
- preemption, interrupts, or whatever are completely futile.
- This is most obvious in preemptible user-level
- environments and in virtualized environments (where
- a given guest OS's VCPUs can be preempted at any time by
- the underlying hypervisor), but can also happen in bare-metal
- environments due to ECC errors, NMIs, and other hardware
- events.
- Although a delay of more than about 20 seconds can result
- in splats, the RCU implementation is obligated to use
- algorithms that can tolerate extremely long delays, but where
- “extremely long” is not long enough to allow
- wrap-around when incrementing a 64-bit counter.
-<li> Both the compiler and the CPU can reorder memory accesses.
- Where it matters, RCU must use compiler directives and
- memory-barrier instructions to preserve ordering.
-<li> Conflicting writes to memory locations in any given cache line
- will result in expensive cache misses.
- Greater numbers of concurrent writes and more-frequent
- concurrent writes will result in more dramatic slowdowns.
- RCU is therefore obligated to use algorithms that have
- sufficient locality to avoid significant performance and
- scalability problems.
-<li> As a rough rule of thumb, only one CPU's worth of processing
- may be carried out under the protection of any given exclusive
- lock.
- RCU must therefore use scalable locking designs.
-<li> Counters are finite, especially on 32-bit systems.
- RCU's use of counters must therefore tolerate counter wrap,
- or be designed such that counter wrap would take way more
- time than a single system is likely to run.
- An uptime of ten years is quite possible, a runtime
- of a century much less so.
- As an example of the latter, RCU's dyntick-idle nesting counter
- allows 54 bits for interrupt nesting level (this counter
- is 64 bits even on a 32-bit system).
- Overflowing this counter requires 2<sup>54</sup>
- half-interrupts on a given CPU without that CPU ever going idle.
- If a half-interrupt happened every microsecond, it would take
- 570 years of runtime to overflow this counter, which is currently
- believed to be an acceptably long time.
-<li> Linux systems can have thousands of CPUs running a single
- Linux kernel in a single shared-memory environment.
- RCU must therefore pay close attention to high-end scalability.
-</ol>
-
-<p>
-This last parallelism fact of life means that RCU must pay special
-attention to the preceding facts of life.
-The idea that Linux might scale to systems with thousands of CPUs would
-have been met with some skepticism in the 1990s, but these requirements
-would have otherwise have been unsurprising, even in the early 1990s.
-
-<h2><a name="Quality-of-Implementation Requirements">Quality-of-Implementation Requirements</a></h2>
-
-<p>
-These sections list quality-of-implementation requirements.
-Although an RCU implementation that ignores these requirements could
-still be used, it would likely be subject to limitations that would
-make it inappropriate for industrial-strength production use.
-Classes of quality-of-implementation requirements are as follows:
-
-<ol>
-<li> <a href="#Specialization">Specialization</a>
-<li> <a href="#Performance and Scalability">Performance and Scalability</a>
-<li> <a href="#Composability">Composability</a>
-<li> <a href="#Corner Cases">Corner Cases</a>
-</ol>
-
-<p>
-These classes is covered in the following sections.
-
-<h3><a name="Specialization">Specialization</a></h3>
-
-<p>
-RCU is and always has been intended primarily for read-mostly situations, as
-illustrated by the following figure.
-This means that RCU's read-side primitives are optimized, often at the
-expense of its update-side primitives.
-
-<p><img src="RCUApplicability.svg" alt="RCUApplicability.svg" width="70%"></p>
-
-<p>
-This focus on read-mostly situations means that RCU must interoperate
-with other synchronization primitives.
-For example, the <tt>add_gp()</tt> and <tt>remove_gp_synchronous()</tt>
-examples discussed earlier use RCU to protect readers and locking to
-coordinate updaters.
-However, the need extends much farther, requiring that a variety of
-synchronization primitives be legal within RCU read-side critical sections,
-including spinlocks, sequence locks, atomic operations, reference
-counters, and memory barriers.
-
-<p>@@QQ@@
-What about sleeping locks?
-<p>@@QQA@@
-These are forbidden within Linux-kernel RCU read-side critical sections
-because it is not legal to place a quiescent state (in this case,
-voluntary context switch) within an RCU read-side critical section.
-However, sleeping locks may be used within userspace RCU read-side critical
-sections, and also within Linux-kernel sleepable RCU
-<a href="#Sleepable RCU">(SRCU)</a>
-read-side critical sections.
-In addition, the -rt patchset turns spinlocks into a sleeping locks so
-that the corresponding critical sections can be preempted, which
-also means that these sleeplockified spinlocks (but not other sleeping locks!)
-may be acquire within -rt-Linux-kernel RCU read-side critical sections.
-
-<p>
-Note that it <i>is</i> legal for a normal RCU read-side critical section
-to conditionally acquire a sleeping locks (as in <tt>mutex_trylock()</tt>),
-but only as long as it does not loop indefinitely attempting to
-conditionally acquire that sleeping locks.
-The key point is that things like <tt>mutex_trylock()</tt>
-either return with the mutex held, or return an error indication if
-the mutex was not immediately available.
-Either way, <tt>mutex_trylock()</tt> returns immediately without sleeping.
-<p>@@QQE@@
-
-<p>
-It often comes as a surprise that many algorithms do not require a
-consistent view of data, but many can function in that mode,
-with network routing being the poster child.
-Internet routing algorithms take significant time to propagate
-updates, so that by the time an update arrives at a given system,
-that system has been sending network traffic the wrong way for
-a considerable length of time.
-Having a few threads continue to send traffic the wrong way for a
-few more milliseconds is clearly not a problem: In the worst case,
-TCP retransmissions will eventually get the data where it needs to go.
-In general, when tracking the state of the universe outside of the
-computer, some level of inconsistency must be tolerated due to
-speed-of-light delays if nothing else.
-
-<p>
-Furthermore, uncertainty about external state is inherent in many cases.
-For example, a pair of veternarians might use heartbeat to determine
-whether or not a given cat was alive.
-But how long should they wait after the last heartbeat to decide that
-the cat is in fact dead?
-Waiting less than 400 milliseconds makes no sense because this would
-mean that a relaxed cat would be considered to cycle between death
-and life more than 100 times per minute.
-Moreover, just as with human beings, a cat's heart might stop for
-some period of time, so the exact wait period is a judgment call.
-One of our pair of veternarians might wait 30 seconds before pronouncing
-the cat dead, while the other might insist on waiting a full minute.
-The two veternarians would then disagree on the state of the cat during
-the final 30 seconds of the minute following the last heartbeat, as
-fancifully illustrated below:
-
-<p><img src="2013-08-is-it-dead.png" alt="2013-08-is-it-dead.png" width="431"></p>
-
-<p>
-Interestingly enough, this same situation applies to hardware.
-When push comes to shove, how do we tell whether or not some
-external server has failed?
-We send messages to it periodically, and declare it failed if we
-don't receive a response within a given period of time.
-Policy decisions can usually tolerate short
-periods of inconsistency.
-The policy was decided some time ago, and is only now being put into
-effect, so a few milliseconds of delay is normally inconsequential.
-
-<p>
-However, there are algorithms that absolutely must see consistent data.
-For example, the translation between a user-level SystemV semaphore
-ID to the corresponding in-kernel data structure is protected by RCU,
-but it is absolutely forbidden to update a semaphore that has just been
-removed.
-In the Linux kernel, this need for consistency is accommodated by acquiring
-spinlocks located in the in-kernel data structure from within
-the RCU read-side critical section, and this is indicated by the
-green box in the figure above.
-Many other techniques may be used, and are in fact used within the
-Linux kernel.
-
-<p>
-In short, RCU is not required to maintain consistency, and other
-mechanisms may be used in concert with RCU when consistency is required.
-RCU's specialization allows it to do its job extremely well, and its
-ability to interoperate with other synchronization mechanisms allows
-the right mix of synchronization tools to be used for a given job.
-
-<h3><a name="Performance and Scalability">Performance and Scalability</a></h3>
-
-<p>
-Energy efficiency is a critical component of performance today,
-and Linux-kernel RCU implementations must therefore avoid unnecessarily
-awakening idle CPUs.
-I cannot claim that this requirement was premeditated.
-In fact, I learned of it during a telephone conversation in which I
-was given “frank and open” feedback on the importance
-of energy efficiency in battery-powered systems and on specific
-energy-efficiency shortcomings of the Linux-kernel RCU implementation.
-In my experience, the battery-powered embedded community will consider
-any unnecessary wakeups to be extremely unfriendly acts.
-So much so that mere Linux-kernel-mailing-list posts are
-insufficient to vent their ire.
-
-<p>
-Memory consumption is not particularly important for in most
-situations, and has become decreasingly
-so as memory sizes have expanded and memory
-costs have plummeted.
-However, as I learned from Matt Mackall's
-<a href="http://elinux.org/Linux_Tiny-FAQ">bloatwatch</a>
-efforts, memory footprint is critically important on single-CPU systems with
-non-preemptible (<tt>CONFIG_PREEMPT=n</tt>) kernels, and thus
-<a href="https://lkml.kernel.org/g/20090113221724.GA15307@linux.vnet.ibm.com">tiny RCU</a>
-was born.
-Josh Triplett has since taken over the small-memory banner with his
-<a href="https://tiny.wiki.kernel.org/">Linux kernel tinification</a>
-project, which resulted in
-<a href="#Sleepable RCU">SRCU</a>
-becoming optional for those kernels not needing it.
-
-<p>
-The remaining performance requirements are, for the most part,
-unsurprising.
-For example, in keeping with RCU's read-side specialization,
-<tt>rcu_dereference()</tt> should have negligible overhead (for
-example, suppression of a few minor compiler optimizations).
-Similarly, in non-preemptible environments, <tt>rcu_read_lock()</tt> and
-<tt>rcu_read_unlock()</tt> should have exactly zero overhead.
-
-<p>
-In preemptible environments, in the case where the RCU read-side
-critical section was not preempted (as will be the case for the
-highest-priority real-time process), <tt>rcu_read_lock()</tt> and
-<tt>rcu_read_unlock()</tt> should have minimal overhead.
-In particular, they should not contain atomic read-modify-write
-operations, memory-barrier instructions, preemption disabling,
-interrupt disabling, or backwards branches.
-However, in the case where the RCU read-side critical section was preempted,
-<tt>rcu_read_unlock()</tt> may acquire spinlocks and disable interrupts.
-This is why it is better to nest an RCU read-side critical section
-within a preempt-disable region than vice versa, at least in cases
-where that critical section is short enough to avoid unduly degrading
-real-time latencies.
-
-<p>
-The <tt>synchronize_rcu()</tt> grace-period-wait primitive is
-optimized for throughput.
-It may therefore incur several milliseconds of latency in addition to
-the duration of the longest RCU read-side critical section.
-On the other hand, multiple concurrent invocations of
-<tt>synchronize_rcu()</tt> are required to use batching optimizations
-so that they can be satisfied by a single underlying grace-period-wait
-operation.
-For example, in the Linux kernel, it is not unusual for a single
-grace-period-wait operation to serve more than
-<a href="https://www.usenix.org/conference/2004-usenix-annual-technical-conference/making-rcu-safe-deep-sub-millisecond-response">1,000 separate invocations</a>
-of <tt>synchronize_rcu()</tt>, thus amortizing the per-invocation
-overhead down to nearly zero.
-However, the grace-period optimization is also required to avoid
-measurable degradation of real-time scheduling and interrupt latencies.
-
-<p>
-In some cases, the multi-millisecond <tt>synchronize_rcu()</tt>
-latencies are unacceptable.
-In these cases, <tt>synchronize_rcu_expedited()</tt> may be used
-instead, reducing the grace-period latency down to a few tens of
-microseconds on small systems, at least in cases where the RCU read-side
-critical sections are short.
-There are currently no special latency requirements for
-<tt>synchronize_rcu_expedited()</tt> on large systems, but,
-consistent with the empirical nature of the RCU specification,
-that is subject to change.
-However, there most definitely are scalability requirements:
-A storm of <tt>synchronize_rcu_expedited()</tt> invocations on 4096
-CPUs should at least make reasonable forward progress.
-In return for its shorter latencies, <tt>synchronize_rcu_expedited()</tt>
-is permitted to impose modest degradation of real-time latency
-on non-idle online CPUs.
-That said, it will likely be necessary to take further steps to reduce this
-degradation, hopefully to roughly that of a scheduling-clock interrupt.
-
-<p>
-There are a number of situations where even
-<tt>synchronize_rcu_expedited()</tt>'s reduced grace-period
-latency is unacceptable.
-In these situations, the asynchronous <tt>call_rcu()</tt> can be
-used in place of <tt>synchronize_rcu()</tt> as follows:
-
-<blockquote>
-<pre>
- 1 struct foo {
- 2 int a;
- 3 int b;
- 4 struct rcu_head rh;
- 5 };
- 6
- 7 static void remove_gp_cb(struct rcu_head *rhp)
- 8 {
- 9 struct foo *p = container_of(rhp, struct foo, rh);
-10
-11 kfree(p);
-12 }
-13
-14 bool remove_gp_asynchronous(void)
-15 {
-16 struct foo *p;
-17
-18 spin_lock(&gp_lock);
-19 p = rcu_dereference(gp);
-20 if (!p) {
-21 spin_unlock(&gp_lock);
-22 return false;
-23 }
-24 rcu_assign_pointer(gp, NULL);
-25 call_rcu(&p->rh, remove_gp_cb);
-26 spin_unlock(&gp_lock);
-27 return true;
-28 }
-</pre>
-</blockquote>
-
-<p>
-A definition of <tt>struct foo</tt> is finally needed, and appears
-on lines 1-5.
-The function <tt>remove_gp_cb()</tt> is passed to <tt>call_rcu()</tt>
-on line 25, and will be invoked after the end of a subsequent
-grace period.
-This gets the same effect as <tt>remove_gp_synchronous()</tt>,
-but without forcing the updater to wait for a grace period to elapse.
-The <tt>call_rcu()</tt> function may be used in a number of
-situations where neither <tt>synchronize_rcu()</tt> nor
-<tt>synchronize_rcu_expedited()</tt> would be legal,
-including within preempt-disable code, <tt>local_bh_disable()</tt> code,
-interrupt-disable code, and interrupt handlers.
-However, even <tt>call_rcu()</tt> is illegal within NMI handlers.
-The callback function (<tt>remove_gp_cb()</tt> in this case) will be
-executed within softirq (software interrupt) environment within the
-Linux kernel,
-either within a real softirq handler or under the protection
-of <tt>local_bh_disable()</tt>.
-In both the Linux kernel and in userspace, it is bad practice to
-write an RCU callback function that takes too long.
-Long-running operations should be relegated to separate threads or
-(in the Linux kernel) workqueues.
-
-<p>@@QQ@@
-Why does line 19 use <tt>rcu_access_pointer()</tt>?
-After all, <tt>call_rcu()</tt> on line 25 stores into the
-structure, which would interact badly with concurrent insertions.
-Doesn't this mean that <tt>rcu_dereference()</tt> is required?
-<p>@@QQA@@
-Presumably the <tt>->gp_lock</tt> acquired on line 18 excludes
-any changes, including any insertions that <tt>rcu_dereference()</tt>
-would protect against.
-Therefore, any insertions will be delayed until after <tt>->gp_lock</tt>
-is released on line 25, which in turn means that
-<tt>rcu_access_pointer()</tt> suffices.
-<p>@@QQE@@
-
-<p>
-However, all that <tt>remove_gp_cb()</tt> is doing is
-invoking <tt>kfree()</tt> on the data element.
-This is a common idiom, and is supported by <tt>kfree_rcu()</tt>,
-which allows “fire and forget” operation as shown below:
-
-<blockquote>
-<pre>
- 1 struct foo {
- 2 int a;
- 3 int b;
- 4 struct rcu_head rh;
- 5 };
- 6
- 7 bool remove_gp_faf(void)
- 8 {
- 9 struct foo *p;
-10
-11 spin_lock(&gp_lock);
-12 p = rcu_dereference(gp);
-13 if (!p) {
-14 spin_unlock(&gp_lock);
-15 return false;
-16 }
-17 rcu_assign_pointer(gp, NULL);
-18 kfree_rcu(p, rh);
-19 spin_unlock(&gp_lock);
-20 return true;
-21 }
-</pre>
-</blockquote>
-
-<p>
-Note that <tt>remove_gp_faf()</tt> simply invokes
-<tt>kfree_rcu()</tt> and proceeds, without any need to pay any
-further attention to the subsequent grace period and <tt>kfree()</tt>.
-It is permissible to invoke <tt>kfree_rcu()</tt> from the same
-environments as for <tt>call_rcu()</tt>.
-Interestingly enough, DYNIX/ptx had the equivalents of
-<tt>call_rcu()</tt> and <tt>kfree_rcu()</tt>, but not
-<tt>synchronize_rcu()</tt>.
-This was due to the fact that RCU was not heavily used within DYNIX/ptx,
-so the very few places that needed something like
-<tt>synchronize_rcu()</tt> simply open-coded it.
-
-<p>@@QQ@@
-Earlier it was claimed that <tt>call_rcu()</tt> and
-<tt>kfree_rcu()</tt> allowed updaters to avoid being blocked
-by readers.
-But how can that be correct, given that the invocation of the callback
-and the freeing of the memory (respectively) must still wait for
-a grace period to elapse?
-<p>@@QQA@@
-We could define things this way, but keep in mind that this sort of
-definition would say that updates in garbage-collected languages
-cannot complete until the next time the garbage collector runs,
-which does not seem at all reasonable.
-The key point is that in most cases, an updater using either
-<tt>call_rcu()</tt> or <tt>kfree_rcu()</tt> can proceed to the
-next update as soon as it has invoked <tt>call_rcu()</tt> or
-<tt>kfree_rcu()</tt>, without having to wait for a subsequent
-grace period.
-<p>@@QQE@@
-
-<p>
-But what if the updater must wait for the completion of code to be
-executed after the end of the grace period, but has other tasks
-that can be carried out in the meantime?
-The polling-style <tt>get_state_synchronize_rcu()</tt> and
-<tt>cond_synchronize_rcu()</tt> functions may be used for this
-purpose, as shown below:
-
-<blockquote>
-<pre>
- 1 bool remove_gp_poll(void)
- 2 {
- 3 struct foo *p;
- 4 unsigned long s;
- 5
- 6 spin_lock(&gp_lock);
- 7 p = rcu_access_pointer(gp);
- 8 if (!p) {
- 9 spin_unlock(&gp_lock);
-10 return false;
-11 }
-12 rcu_assign_pointer(gp, NULL);
-13 spin_unlock(&gp_lock);
-14 s = get_state_synchronize_rcu();
-15 do_something_while_waiting();
-16 cond_synchronize_rcu(s);
-17 kfree(p);
-18 return true;
-19 }
-</pre>
-</blockquote>
-
-<p>
-On line 14, <tt>get_state_synchronize_rcu()</tt> obtains a
-“cookie” from RCU,
-then line 15 carries out other tasks,
-and finally, line 16 returns immediately if a grace period has
-elapsed in the meantime, but otherwise waits as required.
-The need for <tt>get_state_synchronize_rcu</tt> and
-<tt>cond_synchronize_rcu()</tt> has appeared quite recently,
-so it is too early to tell whether they will stand the test of time.
-
-<p>
-RCU thus provides a range of tools to allow updaters to strike the
-required tradeoff between latency, flexibility and CPU overhead.
-
-<h3><a name="Composability">Composability</a></h3>
-
-<p>
-Composability has received much attention in recent years, perhaps in part
-due to the collision of multicore hardware with object-oriented techniques
-designed in single-threaded environments for single-threaded use.
-And in theory, RCU read-side critical sections may be composed, and in
-fact may be nested arbitrarily deeply.
-In practice, as with all real-world implementations of composable
-constructs, there are limitations.
-
-<p>
-Implementations of RCU for which <tt>rcu_read_lock()</tt>
-and <tt>rcu_read_unlock()</tt> generate no code, such as
-Linux-kernel RCU when <tt>CONFIG_PREEMPT=n</tt>, can be
-nested arbitrarily deeply.
-After all, there is no overhead.
-Except that if all these instances of <tt>rcu_read_lock()</tt>
-and <tt>rcu_read_unlock()</tt> are visible to the compiler,
-compilation will eventually fail due to exhausting memory,
-mass storage, or user patience, whichever comes first.
-If the nesting is not visible to the compiler, as is the case with
-mutually recursive functions each in its own translation unit,
-stack overflow will result.
-If the nesting takes the form of loops, either the control variable
-will overflow or (in the Linux kernel) you will get an RCU CPU stall warning.
-Nevertheless, this class of RCU implementations is one
-of the most composable constructs in existence.
-
-<p>
-RCU implementations that explicitly track nesting depth
-are limited by the nesting-depth counter.
-For example, the Linux kernel's preemptible RCU limits nesting to
-<tt>INT_MAX</tt>.
-This should suffice for almost all practical purposes.
-That said, a consecutive pair of RCU read-side critical sections
-between which there is an operation that waits for a grace period
-cannot be enclosed in another RCU read-side critical section.
-This is because it is not legal to wait for a grace period within
-an RCU read-side critical section: To do so would result either
-in deadlock or
-in RCU implicitly splitting the enclosing RCU read-side critical
-section, neither of which is conducive to a long-lived and prosperous
-kernel.
-
-<p>
-It is worth noting that RCU is not alone in limiting composability.
-For example, many transactional-memory implementations prohibit
-composing a pair of transactions separated by an irrevocable
-operation (for example, a network receive operation).
-For another example, lock-based critical sections can be composed
-surprisingly freely, but only if deadlock is avoided.
-
-<p>
-In short, although RCU read-side critical sections are highly composable,
-care is required in some situations, just as is the case for any other
-composable synchronization mechanism.
-
-<h3><a name="Corner Cases">Corner Cases</a></h3>
-
-<p>
-A given RCU workload might have an endless and intense stream of
-RCU read-side critical sections, perhaps even so intense that there
-was never a point in time during which there was not at least one
-RCU read-side critical section in flight.
-RCU cannot allow this situation to block grace periods: As long as
-all the RCU read-side critical sections are finite, grace periods
-must also be finite.
-
-<p>
-That said, preemptible RCU implementations could potentially result
-in RCU read-side critical sections being preempted for long durations,
-which has the effect of creating a long-duration RCU read-side
-critical section.
-This situation can arise only in heavily loaded systems, but systems using
-real-time priorities are of course more vulnerable.
-Therefore, RCU priority boosting is provided to help deal with this
-case.
-That said, the exact requirements on RCU priority boosting will likely
-evolve as more experience accumulates.
-
-<p>
-Other workloads might have very high update rates.
-Although one can argue that such workloads should instead use
-something other than RCU, the fact remains that RCU must
-handle such workloads gracefully.
-This requirement is another factor driving batching of grace periods,
-but it is also the driving force behind the checks for large numbers
-of queued RCU callbacks in the <tt>call_rcu()</tt> code path.
-Finally, high update rates should not delay RCU read-side critical
-sections, although some read-side delays can occur when using
-<tt>synchronize_rcu_expedited()</tt>, courtesy of this function's use
-of <tt>try_stop_cpus()</tt>.
-(In the future, <tt>synchronize_rcu_expedited()</tt> will be
-converted to use lighter-weight inter-processor interrupts (IPIs),
-but this will still disturb readers, though to a much smaller degree.)
-
-<p>
-Although all three of these corner cases were understood in the early
-1990s, a simple user-level test consisting of <tt>close(open(path))</tt>
-in a tight loop
-in the early 2000s suddenly provided a much deeper appreciation of the
-high-update-rate corner case.
-This test also motivated addition of some RCU code to react to high update
-rates, for example, if a given CPU finds itself with more than 10,000
-RCU callbacks queued, it will cause RCU to take evasive action by
-more aggressively starting grace periods and more aggressively forcing
-completion of grace-period processing.
-This evasive action causes the grace period to complete more quickly,
-but at the cost of restricting RCU's batching optimizations, thus
-increasing the CPU overhead incurred by that grace period.
-
-<h2><a name="Software-Engineering Requirements">
-Software-Engineering Requirements</a></h2>
-
-<p>
-Between Murphy's Law and “To err is human”, it is necessary to
-guard against mishaps and misuse:
-
-<ol>
-<li> It is all too easy to forget to use <tt>rcu_read_lock()</tt>
- everywhere that it is needed, so kernels built with
- <tt>CONFIG_PROVE_RCU=y</tt> will spat if
- <tt>rcu_dereference()</tt> is used outside of an
- RCU read-side critical section.
- Update-side code can use <tt>rcu_dereference_protected()</tt>,
- which takes a
- <a href="https://lwn.net/Articles/371986/">lockdep expression</a>
- to indicate what is providing the protection.
- If the indicated protection is not provided, a lockdep splat
- is emitted.
-
- <p>
- Code shared between readers and updaters can use
- <tt>rcu_dereference_check()</tt>, which also takes a
- lockdep expression, and emits a lockdep splat if neither
- <tt>rcu_read_lock()</tt> nor the indicated protection
- is in place.
- In addition, <tt>rcu_dereference_raw()</tt> is used in those
- (hopefully rare) cases where the required protection cannot
- be easily described.
- Finally, <tt>rcu_read_lock_held()</tt> is provided to
- allow a function to verify that it has been invoked within
- an RCU read-side critical section.
- I was made aware of this set of requirements shortly after Thomas
- Gleixner audited a number of RCU uses.
-<li> A given function might wish to check for RCU-related preconditions
- upon entry, before using any other RCU API.
- The <tt>rcu_lockdep_assert()</tt> does this job,
- asserting the expression in kernels having lockdep enabled
- and doing nothing otherwise.
-<li> It is also easy to forget to use <tt>rcu_assign_pointer()</tt>
- and <tt>rcu_dereference()</tt>, perhaps (incorrectly)
- substituting a simple assignment.
- To catch this sort of error, a given RCU-protected pointer may be
- tagged with <tt>__rcu</tt>, after which running sparse
- with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt> will complain
- about simple-assignment accesses to that pointer.
- Arnd Bergmann made me aware of this requirement, and also
- supplied the needed
- <a href="https://lwn.net/Articles/376011/">patch series</a>.
-<li> Kernels built with <tt>CONFIG_DEBUG_OBJECTS_RCU_HEAD=y</tt>
- will splat if a data element is passed to <tt>call_rcu()</tt>
- twice in a row, without a grace period in between.
- (This error is similar to a double free.)
- The corresponding <tt>rcu_head</tt> structures that are
- dynamically allocated are automatically tracked, but
- <tt>rcu_head</tt> structures allocated on the stack
- must be initialized with <tt>init_rcu_head_on_stack()</tt>
- and cleaned up with <tt>destroy_rcu_head_on_stack()</tt>.
- Similarly, statically allocated non-stack <tt>rcu_head</tt>
- structures must be initialized with <tt>init_rcu_head()</tt>
- and cleaned up with <tt>destroy_rcu_head()</tt>.
- Mathieu Desnoyers made me aware of this requirement, and also
- supplied the needed
- <a href="https://lkml.kernel.org/g/20100319013024.GA28456@Krystal">patch</a>.
-<li> An infinite loop in an RCU read-side critical section will
- eventually trigger an RCU CPU stall warning splat, with
- the duration of “eventually” being controlled by the
- <tt>RCU_CPU_STALL_TIMEOUT</tt> <tt>Kconfig</tt> option, or,
- alternatively, by the
- <tt>rcupdate.rcu_cpu_stall_timeout</tt> boot/sysfs
- parameter.
- However, RCU is not obligated to produce this splat
- unless there is a grace period waiting on that particular
- RCU read-side critical section.
- <p>
- Some extreme workloads might intentionally delay
- RCU grace periods, and systems running those workloads can
- be booted with <tt>rcupdate.rcu_cpu_stall_suppress</tt>
- to suppress the splats.
- This kernel parameter may also be set via <tt>sysfs</tt>.
- Furthermore, RCU CPU stall warnings are counter-productive
- during sysrq dumps and during panics.
- RCU therefore supplies the <tt>rcu_sysrq_start()</tt> and
- <tt>rcu_sysrq_end()</tt> API members to be called before
- and after long sysrq dumps.
- RCU also supplies the <tt>rcu_panic()</tt> notifier that is
- automatically invoked at the beginning of a panic to suppress
- further RCU CPU stall warnings.
-
- <p>
- This requirement made itself known in the early 1990s, pretty
- much the first time that it was necessary to debug a CPU stall.
- That said, the initial implementation in DYNIX/ptx was quite
- generic in comparison with that of Linux.
-<li> Although it would be very good to detect pointers leaking out
- of RCU read-side critical sections, there is currently no
- good way of doing this.
- One complication is the need to distinguish between pointers
- leaking and pointers that have been handed off from RCU to
- some other synchronization mechanism, for example, reference
- counting.
-<li> In kernels built with <tt>CONFIG_RCU_TRACE=y</tt>, RCU-related
- information is provided via both debugfs and event tracing.
-<li> Open-coded use of <tt>rcu_assign_pointer()</tt> and
- <tt>rcu_dereference()</tt> to create typical linked
- data structures can be surprisingly error-prone.
- Therefore, RCU-protected
- <a href="https://lwn.net/Articles/609973/#RCU List APIs">linked lists</a>
- and, more recently, RCU-protected
- <a href="https://lwn.net/Articles/612100/">hash tables</a>
- are available.
- Many other special-purpose RCU-protected data structures are
- available in the Linux kernel and the userspace RCU library.
-<li> Some linked structures are created at compile time, but still
- require <tt>__rcu</tt> checking.
- The <tt>RCU_POINTER_INITIALIZER()</tt> macro serves this
- purpose.
-<li> It is not necessary to use <tt>rcu_assign_pointer()</tt>
- when creating linked structures that are to be published via
- a single external pointer.
- The <tt>RCU_INIT_POINTER()</tt> macro is provided for
- this task and also for assigning <tt>NULL</tt> pointers
- at runtime.
-</ol>
-
-<p>
-This not a hard-and-fast list: RCU's diagnostic capabilities will
-continue to be guided by the number and type of usage bugs found
-in real-world RCU usage.
-
-<h2><a name="Linux Kernel Complications">Linux Kernel Complications</a></h2>
-
-<p>
-The Linux kernel provides an interesting environment for all kinds of
-software, including RCU.
-Some of the relevant points of interest are as follows:
-
-<ol>
-<li> <a href="#Configuration">Configuration</a>.
-<li> <a href="#Firmware Interface">Firmware Interface</a>.
-<li> <a href="#Early Boot">Early Boot</a>.
-<li> <a href="#Interrupts and NMIs">
- Interrupts and non-maskable interrupts (NMIs)</a>.
-<li> <a href="#Loadable Modules">Loadable Modules</a>.
-<li> <a href="#Hotplug CPU">Hotplug CPU</a>.
-<li> <a href="#Scheduler and RCU">Scheduler and RCU</a>.
-<li> <a href="#Tracing and RCU">Tracing and RCU</a>.
-<li> <a href="#Energy Efficiency">Energy Efficiency</a>.
-<li> <a href="#Memory Efficiency">Memory Efficiency</a>.
-<li> <a href="#Performance, Scalability, Response Time, and Reliability">
- Performance, Scalability, Response Time, and Reliability</a>.
-</ol>
-
-<p>
-This list is probably incomplete, but it does give a feel for the
-most notable Linux-kernel complications.
-Each of the following sections covers one of the above topics.
-
-<h3><a name="Configuration">Configuration</a></h3>
-
-<p>
-RCU's goal is automatic configuration, so that almost nobody
-needs to worry about RCU's <tt>Kconfig</tt> options.
-And for almost all users, RCU does in fact work well
-“out of the box.”
-
-<p>
-However, there are specialized use cases that are handled by
-kernel boot parameters and <tt>Kconfig</tt> options.
-Unfortunately, the <tt>Kconfig</tt> system will explicitly ask users
-about new <tt>Kconfig</tt> options, which requires almost all of them
-be hidden behind a <tt>CONFIG_RCU_EXPERT</tt> <tt>Kconfig</tt> option.
-
-<p>
-This all should be quite obvious, but the fact remains that
-Linus Torvalds recently had to
-<a href="https://lkml.kernel.org/g/CA+55aFy4wcCwaL4okTs8wXhGZ5h-ibecy_Meg9C4MNQrUnwMcg@mail.gmail.com">remind</a>
-me of this requirement.
-
-<h3><a name="Firmware Interface">Firmware Interface</a></h3>
-
-<p>
-In many cases, kernel obtains information about the system from the
-firmware, and sometimes things are lost in translation.
-Or the translation is accurate, but the original message is bogus.
-
-<p>
-For example, some systems' firmware overreports the number of CPUs,
-sometimes by a large factor.
-If RCU naively believed the firmware, as it used to do,
-it would create too many per-CPU kthreads.
-Although the resulting system will still run correctly, the extra
-kthreads needlessly consume memory and can cause confusion
-when they show up in <tt>ps</tt> listings.
-
-<p>
-RCU must therefore wait for a given CPU to actually come online before
-it can allow itself to believe that the CPU actually exists.
-The resulting “ghost CPUs” (which are never going to
-come online) cause a number of
-<a href="https://paulmck.livejournal.com/37494.html">interesting complications</a>.
-
-<h3><a name="Early Boot">Early Boot</a></h3>
-
-<p>
-The Linux kernel's boot sequence is an interesting process,
-and RCU is used early, even before <tt>rcu_init()</tt>
-is invoked.
-In fact, a number of RCU's primitives can be used as soon as the
-initial task's <tt>task_struct</tt> is available and the
-boot CPU's per-CPU variables are set up.
-The read-side primitives (<tt>rcu_read_lock()</tt>,
-<tt>rcu_read_unlock()</tt>, <tt>rcu_dereference()</tt>,
-and <tt>rcu_access_pointer()</tt>) will operate normally very early on,
-as will <tt>rcu_assign_pointer()</tt>.
-
-<p>
-Although <tt>call_rcu()</tt> may be invoked at any
-time during boot, callbacks are not guaranteed to be invoked until after
-the scheduler is fully up and running.
-This delay in callback invocation is due to the fact that RCU does not
-invoke callbacks until it is fully initialized, and this full initialization
-cannot occur until after the scheduler has initialized itself to the
-point where RCU can spawn and run its kthreads.
-In theory, it would be possible to invoke callbacks earlier,
-however, this is not a panacea because there would be severe restrictions
-on what operations those callbacks could invoke.
-
-<p>
-Perhaps surprisingly, <tt>synchronize_rcu()</tt>,
-<a href="#Bottom-Half Flavor"><tt>synchronize_rcu_bh()</tt></a>
-(<a href="#Bottom-Half Flavor">discussed below</a>),
-and
-<a href="#Sched Flavor"><tt>synchronize_sched()</tt></a>
-will all operate normally
-during very early boot, the reason being that there is only one CPU
-and preemption is disabled.
-This means that the call <tt>synchronize_rcu()</tt> (or friends)
-itself is a quiescent
-state and thus a grace period, so the early-boot implementation can
-be a no-op.
-
-<p>
-Both <tt>synchronize_rcu_bh()</tt> and <tt>synchronize_sched()</tt>
-continue to operate normally through the remainder of boot, courtesy
-of the fact that preemption is disabled across their RCU read-side
-critical sections and also courtesy of the fact that there is still
-only one CPU.
-However, once the scheduler starts initializing, preemption is enabled.
-There is still only a single CPU, but the fact that preemption is enabled
-means that the no-op implementation of <tt>synchronize_rcu()</tt> no
-longer works in <tt>CONFIG_PREEMPT=y</tt> kernels.
-Therefore, as soon as the scheduler starts initializing, the early-boot
-fastpath is disabled.
-This means that <tt>synchronize_rcu()</tt> switches to its runtime
-mode of operation where it posts callbacks, which in turn means that
-any call to <tt>synchronize_rcu()</tt> will block until the corresponding
-callback is invoked.
-Unfortunately, the callback cannot be invoked until RCU's runtime
-grace-period machinery is up and running, which cannot happen until
-the scheduler has initialized itself sufficiently to allow RCU's
-kthreads to be spawned.
-Therefore, invoking <tt>synchronize_rcu()</tt> during scheduler
-initialization can result in deadlock.
-
-<p>@@QQ@@
-So what happens with <tt>synchronize_rcu()</tt> during
-scheduler initialization for <tt>CONFIG_PREEMPT=n</tt>
-kernels?
-<p>@@QQA@@
-In <tt>CONFIG_PREEMPT=n</tt> kernel, <tt>synchronize_rcu()</tt>
-maps directly to <tt>synchronize_sched()</tt>.
-Therefore, <tt>synchronize_rcu()</tt> works normally throughout
-boot in <tt>CONFIG_PREEMPT=n</tt> kernels.
-However, your code must also work in <tt>CONFIG_PREEMPT=y</tt> kernels,
-so it is still necessary to avoid invoking <tt>synchronize_rcu()</tt>
-during scheduler initialization.
-<p>@@QQE@@
-
-<p>
-I learned of these boot-time requirements as a result of a series of
-system hangs.
-
-<h3><a name="Interrupts and NMIs">Interrupts and NMIs</a></h3>
-
-<p>
-The Linux kernel has interrupts, and RCU read-side critical sections are
-legal within interrupt handlers and within interrupt-disabled regions
-of code, as are invocations of <tt>call_rcu()</tt>.
-
-<p>
-Some Linux-kernel architectures can enter an interrupt handler from
-non-idle process context, and then just never leave it, instead stealthily
-transitioning back to process context.
-This trick is sometimes used to invoke system calls from inside the kernel.
-These “half-interrupts” mean that RCU has to be very careful
-about how it counts interrupt nesting levels.
-I learned of this requirement the hard way during a rewrite
-of RCU's dyntick-idle code.
-
-<p>
-The Linux kernel has non-maskable interrupts (NMIs), and
-RCU read-side critical sections are legal within NMI handlers.
-Thankfully, RCU update-side primitives, including
-<tt>call_rcu()</tt>, are prohibited within NMI handlers.
-
-<p>
-The name notwithstanding, some Linux-kernel architectures
-can have nested NMIs, which RCU must handle correctly.
-Andy Lutomirski
-<a href="https://lkml.kernel.org/g/CALCETrXLq1y7e_dKFPgou-FKHB6Pu-r8+t-6Ds+8=va7anBWDA@mail.gmail.com">surprised me</a>
-with this requirement;
-he also kindly surprised me with
-<a href="https://lkml.kernel.org/g/CALCETrXSY9JpW3uE6H8WYk81sg56qasA2aqmjMPsq5dOtzso=g@mail.gmail.com">an algorithm</a>
-that meets this requirement.
-
-<h3><a name="Loadable Modules">Loadable Modules</a></h3>
-
-<p>
-The Linux kernel has loadable modules, and these modules can
-also be unloaded.
-After a given module has been unloaded, any attempt to call
-one of its functions results in a segmentation fault.
-The module-unload functions must therefore cancel any
-delayed calls to loadable-module functions, for example,
-any outstanding <tt>mod_timer()</tt> must be dealt with
-via <tt>del_timer_sync()</tt> or similar.
-
-<p>
-Unfortunately, there is no way to cancel an RCU callback;
-once you invoke <tt>call_rcu()</tt>, the callback function is
-going to eventually be invoked, unless the system goes down first.
-Because it is normally considered socially irresponsible to crash the system
-in response to a module unload request, we need some other way
-to deal with in-flight RCU callbacks.
-
-<p>
-RCU therefore provides
-<tt><a href="https://lwn.net/Articles/217484/">rcu_barrier()</a></tt>,
-which waits until all in-flight RCU callbacks have been invoked.
-If a module uses <tt>call_rcu()</tt>, its exit function should therefore
-prevent any future invocation of <tt>call_rcu()</tt>, then invoke
-<tt>rcu_barrier()</tt>.
-In theory, the underlying module-unload code could invoke
-<tt>rcu_barrier()</tt> unconditionally, but in practice this would
-incur unacceptable latencies.
-
-<p>
-Nikita Danilov noted this requirement for an analogous filesystem-unmount
-situation, and Dipankar Sarma incorporated <tt>rcu_barrier()</tt> into RCU.
-The need for <tt>rcu_barrier()</tt> for module unloading became
-apparent later.
-
-<h3><a name="Hotplug CPU">Hotplug CPU</a></h3>
-
-<p>
-The Linux kernel supports CPU hotplug, which means that CPUs
-can come and go.
-It is of course illegal to use any RCU API member from an offline CPU.
-This requirement was present from day one in DYNIX/ptx, but
-on the other hand, the Linux kernel's CPU-hotplug implementation
-is “interesting.”
-
-<p>
-The Linux-kernel CPU-hotplug implementation has notifiers that
-are used to allow the various kernel subsystems (including RCU)
-to respond appropriately to a given CPU-hotplug operation.
-Most RCU operations may be invoked from CPU-hotplug notifiers,
-including even normal synchronous grace-period operations
-such as <tt>synchronize_rcu()</tt>.
-However, expedited grace-period operations such as
-<tt>synchronize_rcu_expedited()</tt> are not supported,
-due to the fact that current implementations block CPU-hotplug
-operations, which could result in deadlock.
-
-<p>
-In addition, all-callback-wait operations such as
-<tt>rcu_barrier()</tt> are also not supported, due to the
-fact that there are phases of CPU-hotplug operations where
-the outgoing CPU's callbacks will not be invoked until after
-the CPU-hotplug operation ends, which could also result in deadlock.
-
-<h3><a name="Scheduler and RCU">Scheduler and RCU</a></h3>
-
-<p>
-RCU depends on the scheduler, and the scheduler uses RCU to
-protect some of its data structures.
-This means the scheduler is forbidden from acquiring
-the runqueue locks and the priority-inheritance locks
-in the middle of an outermost RCU read-side critical section unless either
-(1) it releases them before exiting that same
-RCU read-side critical section, or
-(2) interrupts are disabled across
-that entire RCU read-side critical section.
-This same prohibition also applies (recursively!) to any lock that is acquired
-while holding any lock to which this prohibition applies.
-Adhering to this rule prevents preemptible RCU from invoking
-<tt>rcu_read_unlock_special()</tt> while either runqueue or
-priority-inheritance locks are held, thus avoiding deadlock.
-
-<p>
-Prior to v4.4, it was only necessary to disable preemption across
-RCU read-side critical sections that acquired scheduler locks.
-In v4.4, expedited grace periods started using IPIs, and these
-IPIs could force a <tt>rcu_read_unlock()</tt> to take the slowpath.
-Therefore, this expedited-grace-period change required disabling of
-interrupts, not just preemption.
-
-<p>
-For RCU's part, the preemptible-RCU <tt>rcu_read_unlock()</tt>
-implementation must be written carefully to avoid similar deadlocks.
-In particular, <tt>rcu_read_unlock()</tt> must tolerate an
-interrupt where the interrupt handler invokes both
-<tt>rcu_read_lock()</tt> and <tt>rcu_read_unlock()</tt>.
-This possibility requires <tt>rcu_read_unlock()</tt> to use
-negative nesting levels to avoid destructive recursion via
-interrupt handler's use of RCU.
-
-<p>
-This pair of mutual scheduler-RCU requirements came as a
-<a href="https://lwn.net/Articles/453002/">complete surprise</a>.
-
-<p>
-As noted above, RCU makes use of kthreads, and it is necessary to
-avoid excessive CPU-time accumulation by these kthreads.
-This requirement was no surprise, but RCU's violation of it
-when running context-switch-heavy workloads when built with
-<tt>CONFIG_NO_HZ_FULL=y</tt>
-<a href="http://www.rdrop.com/users/paulmck/scalability/paper/BareMetal.2015.01.15b.pdf">did come as a surprise [PDF]</a>.
-RCU has made good progress towards meeting this requirement, even
-for context-switch-have <tt>CONFIG_NO_HZ_FULL=y</tt> workloads,
-but there is room for further improvement.
-
-<h3><a name="Tracing and RCU">Tracing and RCU</a></h3>
-
-<p>
-It is possible to use tracing on RCU code, but tracing itself
-uses RCU.
-For this reason, <tt>rcu_dereference_raw_notrace()</tt>
-is provided for use by tracing, which avoids the destructive
-recursion that could otherwise ensue.
-This API is also used by virtualization in some architectures,
-where RCU readers execute in environments in which tracing
-cannot be used.
-The tracing folks both located the requirement and provided the
-needed fix, so this surprise requirement was relatively painless.
-
-<h3><a name="Energy Efficiency">Energy Efficiency</a></h3>
-
-<p>
-Interrupting idle CPUs is considered socially unacceptable,
-especially by people with battery-powered embedded systems.
-RCU therefore conserves energy by detecting which CPUs are
-idle, including tracking CPUs that have been interrupted from idle.
-This is a large part of the energy-efficiency requirement,
-so I learned of this via an irate phone call.
-
-<p>
-Because RCU avoids interrupting idle CPUs, it is illegal to
-execute an RCU read-side critical section on an idle CPU.
-(Kernels built with <tt>CONFIG_PROVE_RCU=y</tt> will splat
-if you try it.)
-The <tt>RCU_NONIDLE()</tt> macro and <tt>_rcuidle</tt>
-event tracing is provided to work around this restriction.
-In addition, <tt>rcu_is_watching()</tt> may be used to
-test whether or not it is currently legal to run RCU read-side
-critical sections on this CPU.
-I learned of the need for diagnostics on the one hand
-and <tt>RCU_NONIDLE()</tt> on the other while inspecting
-idle-loop code.
-Steven Rostedt supplied <tt>_rcuidle</tt> event tracing,
-which is used quite heavily in the idle loop.
-
-<p>
-It is similarly socially unacceptable to interrupt an
-<tt>nohz_full</tt> CPU running in userspace.
-RCU must therefore track <tt>nohz_full</tt> userspace
-execution.
-And in
-<a href="https://lwn.net/Articles/558284/"><tt>CONFIG_NO_HZ_FULL_SYSIDLE=y</tt></a>
-kernels, RCU must separately track idle CPUs on the one hand and
-CPUs that are either idle or executing in userspace on the other.
-In both cases, RCU must be able to sample state at two points in
-time, and be able to determine whether or not some other CPU spent
-any time idle and/or executing in userspace.
-
-<p>
-These energy-efficiency requirements have proven quite difficult to
-understand and to meet, for example, there have been more than five
-clean-sheet rewrites of RCU's energy-efficiency code, the last of
-which was finally able to demonstrate
-<a href="http://www.rdrop.com/users/paulmck/realtime/paper/AMPenergy.2013.04.19a.pdf">real energy savings running on real hardware [PDF]</a>.
-As noted earlier,
-I learned of many of these requirements via angry phone calls:
-Flaming me on the Linux-kernel mailing list was apparently not
-sufficient to fully vent their ire at RCU's energy-efficiency bugs!
-
-<h3><a name="Memory Efficiency">Memory Efficiency</a></h3>
-
-<p>
-Although small-memory non-realtime systems can simply use Tiny RCU,
-code size is only one aspect of memory efficiency.
-Another aspect is the size of the <tt>rcu_head</tt> structure
-used by <tt>call_rcu()</tt> and <tt>kfree_rcu()</tt>.
-Although this structure contains nothing more than a pair of pointers,
-it does appear in many RCU-protected data structures, including
-some that are size critical.
-The <tt>page</tt> structure is a case in point, as evidenced by
-the many occurrences of the <tt>union</tt> keyword within that structure.
-
-<p>
-This need for memory efficiency is one reason that RCU uses hand-crafted
-singly linked lists to track the <tt>rcu_head</tt> structures that
-are waiting for a grace period to elapse.
-It is also the reason why <tt>rcu_head</tt> structures do not contain
-debug information, such as fields tracking the file and line of the
-<tt>call_rcu()</tt> or <tt>kfree_rcu()</tt> that posted them.
-Although this information might appear in debug-only kernel builds at some
-point, in the meantime, the <tt>->func</tt> field will often provide
-the needed debug information.
-
-<p>
-However, in some cases, the need for memory efficiency leads to even
-more extreme measures.
-Returning to the <tt>page</tt> structure, the <tt>rcu_head</tt> field
-shares storage with a great many other structures that are used at
-various points in the corresponding page's lifetime.
-In order to correctly resolve certain
-<a href="https://lkml.kernel.org/g/1439976106-137226-1-git-send-email-kirill.shutemov@linux.intel.com">race conditions</a>,
-the Linux kernel's memory-management subsystem needs a particular bit
-to remain zero during all phases of grace-period processing,
-and that bit happens to map to the bottom bit of the
-<tt>rcu_head</tt> structure's <tt>->next</tt> field.
-RCU makes this guarantee as long as <tt>call_rcu()</tt>
-is used to post the callback, as opposed to <tt>kfree_rcu()</tt>
-or some future “lazy”
-variant of <tt>call_rcu()</tt> that might one day be created for
-energy-efficiency purposes.
-
-<h3><a name="Performance, Scalability, Response Time, and Reliability">
-Performance, Scalability, Response Time, and Reliability</a></h3>
-
-<p>
-Expanding on the
-<a href="#Performance and Scalability">earlier discussion</a>,
-RCU is used heavily by hot code paths in performance-critical
-portions of the Linux kernel's networking, security, virtualization,
-and scheduling code paths.
-RCU must therefore use efficient implementations, especially in its
-read-side primitives.
-To that end, it would be good if preemptible RCU's implementation
-of <tt>rcu_read_lock()</tt> could be inlined, however, doing
-this requires resolving <tt>#include</tt> issues with the
-<tt>task_struct</tt> structure.
-
-<p>
-The Linux kernel supports hardware configurations with up to
-4096 CPUs, which means that RCU must be extremely scalable.
-Algorithms that involve frequent acquisitions of global locks or
-frequent atomic operations on global variables simply cannot be
-tolerated within the RCU implementation.
-RCU therefore makes heavy use of a combining tree based on the
-<tt>rcu_node</tt> structure.
-RCU is required to tolerate all CPUs continuously invoking any
-combination of RCU's runtime primitives with minimal per-operation
-overhead.
-In fact, in many cases, increasing load must <i>decrease</i> the
-per-operation overhead, witness the batching optimizations for
-<tt>synchronize_rcu()</tt>, <tt>call_rcu()</tt>,
-<tt>synchronize_rcu_expedited()</tt>, and <tt>rcu_barrier()</tt>.
-As a general rule, RCU must cheerfully accept whatever the
-rest of the Linux kernel decides to throw at it.
-
-<p>
-The Linux kernel is used for real-time workloads, especially
-in conjunction with the
-<a href="https://rt.wiki.kernel.org/index.php/Main_Page">-rt patchset</a>.
-The real-time-latency response requirements are such that the
-traditional approach of disabling preemption across RCU
-read-side critical sections is inappropriate.
-Kernels built with <tt>CONFIG_PREEMPT=y</tt> therefore
-use an RCU implementation that allows RCU read-side critical
-sections to be preempted.
-This requirement made its presence known after users made it
-clear that an earlier
-<a href="https://lwn.net/Articles/107930/">real-time patch</a>
-did not meet their needs, in conjunction with some
-<a href="https://lkml.kernel.org/g/20050318002026.GA2693@us.ibm.com">RCU issues</a>
-encountered by a very early version of the -rt patchset.
-
-<p>
-In addition, RCU must make do with a sub-100-microsecond real-time latency
-budget.
-In fact, on smaller systems with the -rt patchset, the Linux kernel
-provides sub-20-microsecond real-time latencies for the whole kernel,
-including RCU.
-RCU's scalability and latency must therefore be sufficient for
-these sorts of configurations.
-To my surprise, the sub-100-microsecond real-time latency budget
-<a href="http://www.rdrop.com/users/paulmck/realtime/paper/bigrt.2013.01.31a.LCA.pdf">
-applies to even the largest systems [PDF]</a>,
-up to and including systems with 4096 CPUs.
-This real-time requirement motivated the grace-period kthread, which
-also simplified handling of a number of race conditions.
-
-<p>
-Finally, RCU's status as a synchronization primitive means that
-any RCU failure can result in arbitrary memory corruption that can be
-extremely difficult to debug.
-This means that RCU must be extremely reliable, which in
-practice also means that RCU must have an aggressive stress-test
-suite.
-This stress-test suite is called <tt>rcutorture</tt>.
-
-<p>
-Although the need for <tt>rcutorture</tt> was no surprise,
-the current immense popularity of the Linux kernel is posing
-interesting—and perhaps unprecedented—validation
-challenges.
-To see this, keep in mind that there are well over one billion
-instances of the Linux kernel running today, given Android
-smartphones, Linux-powered televisions, and servers.
-This number can be expected to increase sharply with the advent of
-the celebrated Internet of Things.
-
-<p>
-Suppose that RCU contains a race condition that manifests on average
-once per million years of runtime.
-This bug will be occurring about three times per <i>day</i> across
-the installed base.
-RCU could simply hide behind hardware error rates, given that no one
-should really expect their smartphone to last for a million years.
-However, anyone taking too much comfort from this thought should
-consider the fact that in most jurisdictions, a successful multi-year
-test of a given mechanism, which might include a Linux kernel,
-suffices for a number of types of safety-critical certifications.
-In fact, rumor has it that the Linux kernel is already being used
-in production for safety-critical applications.
-I don't know about you, but I would feel quite bad if a bug in RCU
-killed someone.
-Which might explain my recent focus on validation and verification.
-
-<h2><a name="Other RCU Flavors">Other RCU Flavors</a></h2>
-
-<p>
-One of the more surprising things about RCU is that there are now
-no fewer than five <i>flavors</i>, or API families.
-In addition, the primary flavor that has been the sole focus up to
-this point has two different implementations, non-preemptible and
-preemptible.
-The other four flavors are listed below, with requirements for each
-described in a separate section.
-
-<ol>
-<li> <a href="#Bottom-Half Flavor">Bottom-Half Flavor</a>
-<li> <a href="#Sched Flavor">Sched Flavor</a>
-<li> <a href="#Sleepable RCU">Sleepable RCU</a>
-<li> <a href="#Tasks RCU">Tasks RCU</a>
-</ol>
-
-<h3><a name="Bottom-Half Flavor">Bottom-Half Flavor</a></h3>
-
-<p>
-The softirq-disable (AKA “bottom-half”,
-hence the “_bh” abbreviations)
-flavor of RCU, or <i>RCU-bh</i>, was developed by
-Dipankar Sarma to provide a flavor of RCU that could withstand the
-network-based denial-of-service attacks researched by Robert
-Olsson.
-These attacks placed so much networking load on the system
-that some of the CPUs never exited softirq execution,
-which in turn prevented those CPUs from ever executing a context switch,
-which, in the RCU implementation of that time, prevented grace periods
-from ever ending.
-The result was an out-of-memory condition and a system hang.
-
-<p>
-The solution was the creation of RCU-bh, which does
-<tt>local_bh_disable()</tt>
-across its read-side critical sections, and which uses the transition
-from one type of softirq processing to another as a quiescent state
-in addition to context switch, idle, user mode, and offline.
-This means that RCU-bh grace periods can complete even when some of
-the CPUs execute in softirq indefinitely, thus allowing algorithms
-based on RCU-bh to withstand network-based denial-of-service attacks.
-
-<p>
-Because
-<tt>rcu_read_lock_bh()</tt> and <tt>rcu_read_unlock_bh()</tt>
-disable and re-enable softirq handlers, any attempt to start a softirq
-handlers during the
-RCU-bh read-side critical section will be deferred.
-In this case, <tt>rcu_read_unlock_bh()</tt>
-will invoke softirq processing, which can take considerable time.
-One can of course argue that this softirq overhead should be associated
-with the code following the RCU-bh read-side critical section rather
-than <tt>rcu_read_unlock_bh()</tt>, but the fact
-is that most profiling tools cannot be expected to make this sort
-of fine distinction.
-For example, suppose that a three-millisecond-long RCU-bh read-side
-critical section executes during a time of heavy networking load.
-There will very likely be an attempt to invoke at least one softirq
-handler during that three milliseconds, but any such invocation will
-be delayed until the time of the <tt>rcu_read_unlock_bh()</tt>.
-This can of course make it appear at first glance as if
-<tt>rcu_read_unlock_bh()</tt> was executing very slowly.
-
-<p>
-The
-<a href="https://lwn.net/Articles/609973/#RCU Per-Flavor API Table">RCU-bh API</a>
-includes
-<tt>rcu_read_lock_bh()</tt>,
-<tt>rcu_read_unlock_bh()</tt>,
-<tt>rcu_dereference_bh()</tt>,
-<tt>rcu_dereference_bh_check()</tt>,
-<tt>synchronize_rcu_bh()</tt>,
-<tt>synchronize_rcu_bh_expedited()</tt>,
-<tt>call_rcu_bh()</tt>,
-<tt>rcu_barrier_bh()</tt>, and
-<tt>rcu_read_lock_bh_held()</tt>.
-
-<h3><a name="Sched Flavor">Sched Flavor</a></h3>
-
-<p>
-Before preemptible RCU, waiting for an RCU grace period had the
-side effect of also waiting for all pre-existing interrupt
-and NMI handlers.
-However, there are legitimate preemptible-RCU implementations that
-do not have this property, given that any point in the code outside
-of an RCU read-side critical section can be a quiescent state.
-Therefore, <i>RCU-sched</i> was created, which follows “classic”
-RCU in that an RCU-sched grace period waits for for pre-existing
-interrupt and NMI handlers.
-In kernels built with <tt>CONFIG_PREEMPT=n</tt>, the RCU and RCU-sched
-APIs have identical implementations, while kernels built with
-<tt>CONFIG_PREEMPT=y</tt> provide a separate implementation for each.
-
-<p>
-Note well that in <tt>CONFIG_PREEMPT=y</tt> kernels,
-<tt>rcu_read_lock_sched()</tt> and <tt>rcu_read_unlock_sched()</tt>
-disable and re-enable preemption, respectively.
-This means that if there was a preemption attempt during the
-RCU-sched read-side critical section, <tt>rcu_read_unlock_sched()</tt>
-will enter the scheduler, with all the latency and overhead entailed.
-Just as with <tt>rcu_read_unlock_bh()</tt>, this can make it look
-as if <tt>rcu_read_unlock_sched()</tt> was executing very slowly.
-However, the highest-priority task won't be preempted, so that task
-will enjoy low-overhead <tt>rcu_read_unlock_sched()</tt> invocations.
-
-<p>
-The
-<a href="https://lwn.net/Articles/609973/#RCU Per-Flavor API Table">RCU-sched API</a>
-includes
-<tt>rcu_read_lock_sched()</tt>,
-<tt>rcu_read_unlock_sched()</tt>,
-<tt>rcu_read_lock_sched_notrace()</tt>,
-<tt>rcu_read_unlock_sched_notrace()</tt>,
-<tt>rcu_dereference_sched()</tt>,
-<tt>rcu_dereference_sched_check()</tt>,
-<tt>synchronize_sched()</tt>,
-<tt>synchronize_rcu_sched_expedited()</tt>,
-<tt>call_rcu_sched()</tt>,
-<tt>rcu_barrier_sched()</tt>, and
-<tt>rcu_read_lock_sched_held()</tt>.
-However, anything that disables preemption also marks an RCU-sched
-read-side critical section, including
-<tt>preempt_disable()</tt> and <tt>preempt_enable()</tt>,
-<tt>local_irq_save()</tt> and <tt>local_irq_restore()</tt>,
-and so on.
-
-<h3><a name="Sleepable RCU">Sleepable RCU</a></h3>
-
-<p>
-For well over a decade, someone saying “I need to block within
-an RCU read-side critical section” was a reliable indication
-that this someone did not understand RCU.
-After all, if you are always blocking in an RCU read-side critical
-section, you can probably afford to use a higher-overhead synchronization
-mechanism.
-However, that changed with the advent of the Linux kernel's notifiers,
-whose RCU read-side critical
-sections almost never sleep, but sometimes need to.
-This resulted in the introduction of
-<a href="https://lwn.net/Articles/202847/">sleepable RCU</a>,
-or <i>SRCU</i>.
-
-<p>
-SRCU allows different domains to be defined, with each such domain
-defined by an instance of an <tt>srcu_struct</tt> structure.
-A pointer to this structure must be passed in to each SRCU function,
-for example, <tt>synchronize_srcu(&ss)</tt>, where
-<tt>ss</tt> is the <tt>srcu_struct</tt> structure.
-The key benefit of these domains is that a slow SRCU reader in one
-domain does not delay an SRCU grace period in some other domain.
-That said, one consequence of these domains is that read-side code
-must pass a “cookie” from <tt>srcu_read_lock()</tt>
-to <tt>srcu_read_unlock()</tt>, for example, as follows:
-
-<blockquote>
-<pre>
- 1 int idx;
- 2
- 3 idx = srcu_read_lock(&ss);
- 4 do_something();
- 5 srcu_read_unlock(&ss, idx);
-</pre>
-</blockquote>
-
-<p>
-As noted above, it is legal to block within SRCU read-side critical sections,
-however, with great power comes great responsibility.
-If you block forever in one of a given domain's SRCU read-side critical
-sections, then that domain's grace periods will also be blocked forever.
-Of course, one good way to block forever is to deadlock, which can
-happen if any operation in a given domain's SRCU read-side critical
-section can block waiting, either directly or indirectly, for that domain's
-grace period to elapse.
-For example, this results in a self-deadlock:
-
-<blockquote>
-<pre>
- 1 int idx;
- 2
- 3 idx = srcu_read_lock(&ss);
- 4 do_something();
- 5 synchronize_srcu(&ss);
- 6 srcu_read_unlock(&ss, idx);
-</pre>
-</blockquote>
-
-<p>
-However, if line 5 acquired a mutex that was held across
-a <tt>synchronize_srcu()</tt> for domain <tt>ss</tt>,
-deadlock would still be possible.
-Furthermore, if line 5 acquired a mutex that was held across
-a <tt>synchronize_srcu()</tt> for some other domain <tt>ss1</tt>,
-and if an <tt>ss1</tt>-domain SRCU read-side critical section
-acquired another mutex that was held across as <tt>ss</tt>-domain
-<tt>synchronize_srcu()</tt>,
-deadlock would again be possible.
-Such a deadlock cycle could extend across an arbitrarily large number
-of different SRCU domains.
-Again, with great power comes great responsibility.
-
-<p>
-Unlike the other RCU flavors, SRCU read-side critical sections can
-run on idle and even offline CPUs.
-This ability requires that <tt>srcu_read_lock()</tt> and
-<tt>srcu_read_unlock()</tt> contain memory barriers, which means
-that SRCU readers will run a bit slower than would RCU readers.
-It also motivates the <tt>smp_mb__after_srcu_read_unlock()</tt>
-API, which, in combination with <tt>srcu_read_unlock()</tt>,
-guarantees a full memory barrier.
-
-<p>
-The
-<a href="https://lwn.net/Articles/609973/#RCU Per-Flavor API Table">SRCU API</a>
-includes
-<tt>srcu_read_lock()</tt>,
-<tt>srcu_read_unlock()</tt>,
-<tt>srcu_dereference()</tt>,
-<tt>srcu_dereference_check()</tt>,
-<tt>synchronize_srcu()</tt>,
-<tt>synchronize_srcu_expedited()</tt>,
-<tt>call_srcu()</tt>,
-<tt>srcu_barrier()</tt>, and
-<tt>srcu_read_lock_held()</tt>.
-It also includes
-<tt>DEFINE_SRCU()</tt>,
-<tt>DEFINE_STATIC_SRCU()</tt>, and
-<tt>init_srcu_struct()</tt>
-APIs for defining and initializing <tt>srcu_struct</tt> structures.
-
-<h3><a name="Tasks RCU">Tasks RCU</a></h3>
-
-<p>
-Some forms of tracing use “tramopolines” to handle the
-binary rewriting required to install different types of probes.
-It would be good to be able to free old trampolines, which sounds
-like a job for some form of RCU.
-However, because it is necessary to be able to install a trace
-anywhere in the code, it is not possible to use read-side markers
-such as <tt>rcu_read_lock()</tt> and <tt>rcu_read_unlock()</tt>.
-In addition, it does not work to have these markers in the trampoline
-itself, because there would need to be instructions following
-<tt>rcu_read_unlock()</tt>.
-Although <tt>synchronize_rcu()</tt> would guarantee that execution
-reached the <tt>rcu_read_unlock()</tt>, it would not be able to
-guarantee that execution had completely left the trampoline.
-
-<p>
-The solution, in the form of
-<a href="https://lwn.net/Articles/607117/"><i>Tasks RCU</i></a>,
-is to have implicit
-read-side critical sections that are delimited by voluntary context
-switches, that is, calls to <tt>schedule()</tt>,
-<tt>cond_resched_rcu_qs()</tt>, and
-<tt>synchronize_rcu_tasks()</tt>.
-In addition, transitions to and from userspace execution also delimit
-tasks-RCU read-side critical sections.
-
-<p>
-The tasks-RCU API is quite compact, consisting only of
-<tt>call_rcu_tasks()</tt>,
-<tt>synchronize_rcu_tasks()</tt>, and
-<tt>rcu_barrier_tasks()</tt>.
-
-<h2><a name="Possible Future Changes">Possible Future Changes</a></h2>
-
-<p>
-One of the tricks that RCU uses to attain update-side scalability is
-to increase grace-period latency with increasing numbers of CPUs.
-If this becomes a serious problem, it will be necessary to rework the
-grace-period state machine so as to avoid the need for the additional
-latency.
-
-<p>
-Expedited grace periods scan the CPUs, so their latency and overhead
-increases with increasing numbers of CPUs.
-If this becomes a serious problem on large systems, it will be necessary
-to do some redesign to avoid this scalability problem.
-
-<p>
-RCU disables CPU hotplug in a few places, perhaps most notably in the
-expedited grace-period and <tt>rcu_barrier()</tt> operations.
-If there is a strong reason to use expedited grace periods in CPU-hotplug
-notifiers, it will be necessary to avoid disabling CPU hotplug.
-This would introduce some complexity, so there had better be a <i>very</i>
-good reason.
-
-<p>
-The tradeoff between grace-period latency on the one hand and interruptions
-of other CPUs on the other hand may need to be re-examined.
-The desire is of course for zero grace-period latency as well as zero
-interprocessor interrupts undertaken during an expedited grace period
-operation.
-While this ideal is unlikely to be achievable, it is quite possible that
-further improvements can be made.
-
-<p>
-The multiprocessor implementations of RCU use a combining tree that
-groups CPUs so as to reduce lock contention and increase cache locality.
-However, this combining tree does not spread its memory across NUMA
-nodes nor does it align the CPU groups with hardware features such
-as sockets or cores.
-Such spreading and alignment is currently believed to be unnecessary
-because the hotpath read-side primitives do not access the combining
-tree, nor does <tt>call_rcu()</tt> in the common case.
-If you believe that your architecture needs such spreading and alignment,
-then your architecture should also benefit from the
-<tt>rcutree.rcu_fanout_leaf</tt> boot parameter, which can be set
-to the number of CPUs in a socket, NUMA node, or whatever.
-If the number of CPUs is too large, use a fraction of the number of
-CPUs.
-If the number of CPUs is a large prime number, well, that certainly
-is an “interesting” architectural choice!
-More flexible arrangements might be considered, but only if
-<tt>rcutree.rcu_fanout_leaf</tt> has proven inadequate, and only
-if the inadequacy has been demonstrated by a carefully run and
-realistic system-level workload.
-
-<p>
-Please note that arrangements that require RCU to remap CPU numbers will
-require extremely good demonstration of need and full exploration of
-alternatives.
-
-<p>
-There is an embarrassingly large number of flavors of RCU, and this
-number has been increasing over time.
-Perhaps it will be possible to combine some at some future date.
-
-<p>
-RCU's various kthreads are reasonably recent additions.
-It is quite likely that adjustments will be required to more gracefully
-handle extreme loads.
-It might also be necessary to be able to relate CPU utilization by
-RCU's kthreads and softirq handlers to the code that instigated this
-CPU utilization.
-For example, RCU callback overhead might be charged back to the
-originating <tt>call_rcu()</tt> instance, though probably not
-in production kernels.
-
-<h2><a name="Summary">Summary</a></h2>
-
-<p>
-This document has presented more than two decade's worth of RCU
-requirements.
-Given that the requirements keep changing, this will not be the last
-word on this subject, but at least it serves to get an important
-subset of the requirements set forth.
-
-<h2><a name="Acknowledgments">Acknowledgments</a></h2>
-
-I am grateful to Steven Rostedt, Lai Jiangshan, Ingo Molnar,
-Oleg Nesterov, Borislav Petkov, Peter Zijlstra, Boqun Feng, and
-Andy Lutomirski for their help in rendering
-this article human readable, and to Michelle Rankin for her support
-of this effort.
-Other contributions are acknowledged in the Linux kernel's git archive.
-The cartoon is copyright (c) 2013 by Melissa Broussard,
-and is provided
-under the terms of the Creative Commons Attribution-Share Alike 3.0
-United States license.
-
-<p>@@QQAL@@
-
-</body></html>
+++ /dev/null
-#!/bin/sh
-#
-# Usage: sh htmlqqz.sh file
-#
-# Extracts and converts quick quizzes in a proto-HTML document file.htmlx.
-# Commands, all of which must be on a line by themselves:
-#
-# "<p>@@QQ@@": Start of a quick quiz.
-# "<p>@@QQA@@": Start of a quick-quiz answer.
-# "<p>@@QQE@@": End of a quick-quiz answer, and thus of the quick quiz.
-# "<p>@@QQAL@@": Place to put quick-quiz answer list.
-#
-# Places the result in file.html.
-#
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, you can access it online at
-# http://www.gnu.org/licenses/gpl-2.0.html.
-#
-# Copyright (c) 2013 Paul E. McKenney, IBM Corporation.
-
-fn=$1
-if test ! -r $fn.htmlx
-then
- echo "Error: $fn.htmlx unreadable."
- exit 1
-fi
-
-echo "<!-- DO NOT HAND EDIT. -->" > $fn.html
-echo "<!-- Instead, edit $fn.htmlx and run 'sh htmlqqz.sh $fn' -->" >> $fn.html
-awk < $fn.htmlx >> $fn.html '
-
-state == "" && $1 != "<p>@@QQ@@" && $1 != "<p>@@QQAL@@" {
- print $0;
- if ($0 ~ /^<p>@@QQ/)
- print "Bad Quick Quiz command: " NR " (expected <p>@@QQ@@ or <p>@@QQAL@@)." > "/dev/stderr"
- next;
-}
-
-state == "" && $1 == "<p>@@QQ@@" {
- qqn++;
- qqlineno = NR;
- haveqq = 1;
- state = "qq";
- print "<p><a name=\"Quick Quiz " qqn "\"><b>Quick Quiz " qqn "</b>:</a>"
- next;
-}
-
-state == "qq" && $1 != "<p>@@QQA@@" {
- qq[qqn] = qq[qqn] $0 "\n";
- print $0
- if ($0 ~ /^<p>@@QQ/)
- print "Bad Quick Quiz command: " NR ". (expected <p>@@QQA@@)" > "/dev/stderr"
- next;
-}
-
-state == "qq" && $1 == "<p>@@QQA@@" {
- state = "qqa";
- print "<br><a href=\"#qq" qqn "answer\">Answer</a>"
- next;
-}
-
-state == "qqa" && $1 != "<p>@@QQE@@" {
- qqa[qqn] = qqa[qqn] $0 "\n";
- if ($0 ~ /^<p>@@QQ/)
- print "Bad Quick Quiz command: " NR " (expected <p>@@QQE@@)." > "/dev/stderr"
- next;
-}
-
-state == "qqa" && $1 == "<p>@@QQE@@" {
- state = "";
- next;
-}
-
-state == "" && $1 == "<p>@@QQAL@@" {
- haveqq = "";
- print "<h3><a name=\"Answers to Quick Quizzes\">"
- print "Answers to Quick Quizzes</a></h3>"
- print "";
- for (i = 1; i <= qqn; i++) {
- print "<a name=\"qq" i "answer\"></a>"
- print "<p><b>Quick Quiz " i "</b>:"
- print qq[i];
- print "";
- print "</p><p><b>Answer</b>:"
- print qqa[i];
- print "";
- print "</p><p><a href=\"#Quick%20Quiz%20" i "\"><b>Back to Quick Quiz " i "</b>.</a>"
- print "";
- }
- next;
-}
-
-END {
- if (state != "")
- print "Unterminated Quick Quiz: " qqlineno "." > "/dev/stderr"
- else if (haveqq)
- print "Missing \"<p>@@QQAL@@\", no Quick Quiz." > "/dev/stderr"
-}'
The output of "cat rcu/rcu_preempt/rcuexp" looks as follows:
-s=21872 wd0=0 wd1=0 wd2=0 wd3=5 n=0 enq=0 sc=21872
+s=21872 wd1=0 wd2=0 wd3=5 n=0 enq=0 sc=21872
These fields are as follows:
o "s" is the sequence number, with an odd number indicating that
an expedited grace period is in progress.
-o "wd0", "wd1", "wd2", and "wd3" are the number of times that an
- attempt to start an expedited grace period found that someone
- else had completed an expedited grace period that satisfies the
- attempted request. "Our work is done."
+o "wd1", "wd2", and "wd3" are the number of times that an attempt
+ to start an expedited grace period found that someone else had
+ completed an expedited grace period that satisfies the attempted
+ request. "Our work is done."
o "n" is number of times that a concurrent CPU-hotplug operation
forced a fallback to a normal grace period.
RCU is analogous to reader-writer locking. The following unified
diff shows how closely related RCU and reader-writer locking can be.
+ @@ -5,5 +5,5 @@ struct el {
+ int data;
+ /* Other data fields */
+ };
+ -rwlock_t listmutex;
+ +spinlock_t listmutex;
+ struct el head;
+
@@ -13,15 +14,15 @@
struct list_head *lp;
struct el *p;
- - read_lock();
+ - read_lock(&listmutex);
- list_for_each_entry(p, head, lp) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(p, head, lp) {
if (p->key == key) {
*result = p->data;
- - read_unlock();
+ - read_unlock(&listmutex);
+ rcu_read_unlock();
return 1;
}
}
- - read_unlock();
+ - read_unlock(&listmutex);
+ rcu_read_unlock();
return 0;
}
5 int data; 5 int data;
6 /* Other data fields */ 6 /* Other data fields */
7 }; 7 };
- 8 spinlock_t listmutex; 8 spinlock_t listmutex;
+ 8 rwlock_t listmutex; 8 spinlock_t listmutex;
9 struct el head; 9 struct el head;
1 int search(long key, int *result) 1 int search(long key, int *result)
3 struct list_head *lp; 3 struct list_head *lp;
4 struct el *p; 4 struct el *p;
5 5
- 6 read_lock(); 6 rcu_read_lock();
+ 6 read_lock(&listmutex); 6 rcu_read_lock();
7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
8 if (p->key == key) { 8 if (p->key == key) {
9 *result = p->data; 9 *result = p->data;
-10 read_unlock(); 10 rcu_read_unlock();
+10 read_unlock(&listmutex); 10 rcu_read_unlock();
11 return 1; 11 return 1;
12 } 12 }
13 } 13 }
-14 read_unlock(); 14 rcu_read_unlock();
+14 read_unlock(&listmutex); 14 rcu_read_unlock();
15 return 0; 15 return 0;
16 } 16 }
- target-supply : regulator for SATA target power
- phys : reference to the SATA PHY node
- phy-names : must be "sata-phy"
+- ports-implemented : Mask that indicates which ports that the HBA supports
+ are available for software to use. Useful if PORTS_IMPL
+ is not programmed by the BIOS, which is true with
+ some embedded SOC's.
Required properties when using sub-nodes:
- #address-cells : number of cells to encode an address
-Device-Tree binding for regmap
-
-The endianness mode of CPU & Device scenarios:
-Index Device Endianness properties
----------------------------------------------------
-1 BE 'big-endian'
-2 LE 'little-endian'
-3 Native 'native-endian'
-
-For one device driver, which will run in different scenarios above
-on different SoCs using the devicetree, we need one way to simplify
-this.
+Devicetree binding for regmap
Optional properties:
-- {big,little,native}-endian: these are boolean properties, if absent
- then the implementation will choose a default based on the device
- being controlled. These properties are for register values and all
- the buffers only. Native endian means that the CPU and device have
- the same endianness.
-Examples:
-Scenario 1 : CPU in LE mode & device in LE mode.
-dev: dev@40031000 {
- compatible = "name";
- reg = <0x40031000 0x1000>;
- ...
-};
+ little-endian,
+ big-endian,
+ native-endian: See common-properties.txt for a definition
-Scenario 2 : CPU in LE mode & device in BE mode.
-dev: dev@40031000 {
- compatible = "name";
- reg = <0x40031000 0x1000>;
- ...
- big-endian;
-};
+Note:
+Regmap defaults to little-endian register access on MMIO based
+devices, this is by far the most common setting. On CPU
+architectures that typically run big-endian operating systems
+(e.g. PowerPC), registers can be defined as big-endian and must
+be marked that way in the devicetree.
-Scenario 3 : CPU in BE mode & device in BE mode.
-dev: dev@40031000 {
- compatible = "name";
- reg = <0x40031000 0x1000>;
- ...
-};
+On SoCs that can be operated in both big-endian and little-endian
+modes, with a single hardware switch controlling both the endianess
+of the CPU and a byteswap for MMIO registers (e.g. many Broadcom MIPS
+chips), "native-endian" is used to allow using the same device tree
+blob in both cases.
-Scenario 4 : CPU in BE mode & device in LE mode.
+Examples:
+Scenario 1 : a register set in big-endian mode.
dev: dev@40031000 {
- compatible = "name";
+ compatible = "syscon";
reg = <0x40031000 0x1000>;
+ big-endian;
...
- little-endian;
};
Lazy RCU callbacks are those which RCU can
prove do nothing more than free memory.
+ rcuperf.gp_exp= [KNL]
+ Measure performance of expedited synchronous
+ grace-period primitives.
+
+ rcuperf.holdoff= [KNL]
+ Set test-start holdoff period. The purpose of
+ this parameter is to delay the start of the
+ test until boot completes in order to avoid
+ interference.
+
+ rcuperf.nreaders= [KNL]
+ Set number of RCU readers. The value -1 selects
+ N, where N is the number of CPUs. A value
+ "n" less than -1 selects N-n+1, where N is again
+ the number of CPUs. For example, -2 selects N
+ (the number of CPUs), -3 selects N+1, and so on.
+ A value of "n" less than or equal to -N selects
+ a single reader.
+
+ rcuperf.nwriters= [KNL]
+ Set number of RCU writers. The values operate
+ the same as for rcuperf.nreaders.
+ N, where N is the number of CPUs
+
+ rcuperf.perf_runnable= [BOOT]
+ Start rcuperf running at boot time.
+
+ rcuperf.shutdown= [KNL]
+ Shut the system down after performance tests
+ complete. This is useful for hands-off automated
+ testing.
+
+ rcuperf.perf_type= [KNL]
+ Specify the RCU implementation to test.
+
+ rcuperf.verbose= [KNL]
+ Enable additional printk() statements.
+
rcutorture.cbflood_inter_holdoff= [KNL]
Set holdoff time (jiffies) between successive
callback-flood tests.
LCO is a technique for efficiently computing the outer checksum of an
encapsulated datagram when the inner checksum is due to be offloaded.
The ones-complement sum of a correctly checksummed TCP or UDP packet is
- equal to the sum of the pseudo header, because everything else gets
- 'cancelled out' by the checksum field. This is because the sum was
+ equal to the complement of the sum of the pseudo header, because everything
+ else gets 'cancelled out' by the checksum field. This is because the sum was
complemented before being written to the checksum field.
More generally, this holds in any case where the 'IP-style' ones complement
checksum is used, and thus any checksum that TX Checksum Offload supports.
That is, if we have set up TX Checksum Offload with a start/offset pair, we
- know that _after the device has filled in that checksum_, the ones
+ know that after the device has filled in that checksum, the ones
complement sum from csum_start to the end of the packet will be equal to
- _whatever value we put in the checksum field beforehand_. This allows us
- to compute the outer checksum without looking at the payload: we simply
- stop summing when we get to csum_start, then add the 16-bit word at
- (csum_start + csum_offset).
+ the complement of whatever value we put in the checksum field beforehand.
+ This allows us to compute the outer checksum without looking at the payload:
+ we simply stop summing when we get to csum_start, then add the complement of
+ the 16-bit word at (csum_start + csum_offset).
Then, when the true inner checksum is filled in (either by hardware or by
skb_checksum_help()), the outer checksum will become correct by virtue of
the arithmetic.
perf_event_paranoid:
Controls use of the performance events system by unprivileged
-users (without CAP_SYS_ADMIN). The default value is 1.
+users (without CAP_SYS_ADMIN). The default value is 2.
-1: Allow use of (almost) all events by all users
>=0: Disallow raw tracepoint access by users without CAP_IOC_LOCK
F: kernel/trace/
F: tools/testing/selftests/ftrace/
+TRACING MMIO ACCESSES (MMIOTRACE)
+M: Steven Rostedt <rostedt@goodmis.org>
+M: Ingo Molnar <mingo@kernel.org>
+R: Karol Herbst <karolherbst@gmail.com>
+R: Pekka Paalanen <ppaalanen@gmail.com>
+S: Maintained
+L: linux-kernel@vger.kernel.org
+L: nouveau@lists.freedesktop.org
+F: kernel/trace/trace_mmiotrace.c
+F: include/linux/mmiotrace.h
+F: arch/x86/mm/kmmio.c
+F: arch/x86/mm/mmio-mod.c
+F: arch/x86/mm/testmmiotrace.c
+
TRIVIAL PATCHES
M: Jiri Kosina <trivial@kernel.org>
T: git git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial.git
VERSION = 4
PATCHLEVEL = 6
SUBLEVEL = 0
-EXTRAVERSION = -rc6
+EXTRAVERSION =
NAME = Charred Weasel
# *DOCUMENTATION*
pmc: pmc@fffffc00 {
compatible = "atmel,at91sam9x5-pmc", "syscon";
- reg = <0xfffffc00 0x100>;
+ reg = <0xfffffc00 0x200>;
interrupts = <1 IRQ_TYPE_LEVEL_HIGH 7>;
interrupt-controller;
#address-cells = <1>;
};
sata0: sata@29000000 {
- compatible = "generic-ahci";
+ compatible = "qcom,apq8064-ahci", "generic-ahci";
status = "disabled";
reg = <0x29000000 0x180>;
interrupts = <GIC_SPI 209 IRQ_TYPE_NONE>;
phys = <&sata_phy0>;
phy-names = "sata-phy";
+ ports-implemented = <0x1>;
};
/* Temporary fixed regulator */
status = "disabled";
nfc@c0000000 {
- compatible = "atmel,sama5d4-nfc";
+ compatible = "atmel,sama5d3-nfc";
#address-cells = <1>;
#size-cells = <1>;
reg = < /* NFC Command Registers */
#ifndef __ASSEMBLY__
+#ifdef CONFIG_CPU_CP15_MMU
static inline unsigned int get_domain(void)
{
unsigned int domain;
: : "r" (val) : "memory");
isb();
}
+#else
+static inline unsigned int get_domain(void)
+{
+ return 0;
+}
+
+static inline void set_domain(unsigned val)
+{
+}
+#endif
#ifdef CONFIG_CPU_USE_DOMAINS
#define modify_domain(dom,type) \
mov r0, #CONFIG_VECTORS_BASE @ Cover from VECTORS_BASE
ldr r5,=(MPU_AP_PL1RW_PL0NA | MPU_RGN_NORMAL)
/* Writing N to bits 5:1 (RSR_SZ) --> region size 2^N+1 */
- mov r6, #(((PAGE_SHIFT - 1) << MPU_RSR_SZ) | 1 << MPU_RSR_EN)
+ mov r6, #(((2 * PAGE_SHIFT - 1) << MPU_RSR_SZ) | 1 << MPU_RSR_EN)
setup_region r0, r5, r6, MPU_DATA_SIDE @ VECTORS_BASE, PL0 NA, enabled
beq 3f @ Memory-map not unified
/* MPU initialisation functions */
void __init sanity_check_meminfo_mpu(void)
{
- int i;
phys_addr_t phys_offset = PHYS_OFFSET;
phys_addr_t aligned_region_size, specified_mem_size, rounded_mem_size;
struct memblock_region *reg;
} else {
/*
* memblock auto merges contiguous blocks, remove
- * all blocks afterwards
+ * all blocks afterwards in one go (we can't remove
+ * blocks separately while iterating)
*/
pr_notice("Ignoring RAM after %pa, memory at %pa ignored\n",
- &mem_start, ®->base);
- memblock_remove(reg->base, reg->size);
+ &mem_end, ®->base);
+ memblock_remove(reg->base, 0 - reg->base);
+ break;
}
}
pr_warn("Truncating memory from %pa to %pa (MPU region constraints)",
&specified_mem_size, &aligned_region_size);
memblock_remove(mem_start + aligned_region_size,
- specified_mem_size - aligned_round_size);
+ specified_mem_size - aligned_region_size);
mem_end = mem_start + aligned_region_size;
}
return;
region_err = mpu_setup_region(MPU_RAM_REGION, PHYS_OFFSET,
- ilog2(meminfo.bank[0].size),
+ ilog2(memblock.memory.regions[0].size),
MPU_AP_PL1RW_PL0RW | MPU_RGN_NORMAL);
if (region_err) {
panic("MPU region initialization failure! %d", region_err);
* some architectures which the DRAM is the exception vector to trap,
* alloc_page breaks with error, although it is not NULL, but "0."
*/
- memblock_reserve(CONFIG_VECTORS_BASE, PAGE_SIZE);
+ memblock_reserve(CONFIG_VECTORS_BASE, 2 * PAGE_SIZE);
#else /* ifndef CONFIG_CPU_V7M */
/*
* There is no dedicated vector page on V7-M. So nothing needs to be
config ARCH_SUNXI
bool "Allwinner sunxi 64-bit SoC Family"
+ select GENERIC_IRQ_CHIP
help
This enables support for Allwinner sunxi based SoCs like the A64.
case BPF_JGE:
jmp_cond = A64_COND_CS;
break;
+ case BPF_JSET:
case BPF_JNE:
jmp_cond = A64_COND_NE;
break;
CONFIG_9P_FS=y
CONFIG_NET_9P=y
CONFIG_NET_9P_VIRTIO=y
+CONFIG_SCSI_LOWLEVEL=y
+CONFIG_SCSI_VIRTIO=y
+CONFIG_VIRTIO_INPUT=y
375 i386 membarrier sys_membarrier
376 i386 mlock2 sys_mlock2
377 i386 copy_file_range sys_copy_file_range
-378 i386 preadv2 sys_preadv2
-379 i386 pwritev2 sys_pwritev2
+378 i386 preadv2 sys_preadv2 compat_sys_preadv2
+379 i386 pwritev2 sys_pwritev2 compat_sys_pwritev2
c->idxmsk64 |= (1ULL << x86_pmu.num_counters) - 1;
}
c->idxmsk64 &=
- ~(~0UL << (INTEL_PMC_IDX_FIXED + x86_pmu.num_counters_fixed));
+ ~(~0ULL << (INTEL_PMC_IDX_FIXED + x86_pmu.num_counters_fixed));
c->weight = hweight64(c->idxmsk64);
}
}
/* clear STOP and INT from current entry */
buf->topa_index[buf->stop_pos]->stop = 0;
+ buf->topa_index[buf->stop_pos]->intr = 0;
buf->topa_index[buf->intr_pos]->intr = 0;
/* how many pages till the STOP marker */
buf->intr_pos = idx;
buf->topa_index[buf->stop_pos]->stop = 1;
+ buf->topa_index[buf->stop_pos]->intr = 1;
buf->topa_index[buf->intr_pos]->intr = 1;
return 0;
#define KNL_CHA_MSR_PMON_BOX_FILTER_TID 0x1ff
#define KNL_CHA_MSR_PMON_BOX_FILTER_STATE (7 << 18)
#define KNL_CHA_MSR_PMON_BOX_FILTER_OP (0xfffffe2aULL << 32)
+#define KNL_CHA_MSR_PMON_BOX_FILTER_REMOTE_NODE (0x1ULL << 32)
+#define KNL_CHA_MSR_PMON_BOX_FILTER_LOCAL_NODE (0x1ULL << 33)
+#define KNL_CHA_MSR_PMON_BOX_FILTER_NNC (0x1ULL << 37)
/* KNL EDC/MC UCLK */
#define KNL_UCLK_MSR_PMON_CTR0_LOW 0x400
reg1->reg = HSWEP_C0_MSR_PMON_BOX_FILTER0 +
KNL_CHA_MSR_OFFSET * box->pmu->pmu_idx;
reg1->config = event->attr.config1 & knl_cha_filter_mask(idx);
+
+ reg1->config |= KNL_CHA_MSR_PMON_BOX_FILTER_REMOTE_NODE;
+ reg1->config |= KNL_CHA_MSR_PMON_BOX_FILTER_LOCAL_NODE;
+ reg1->config |= KNL_CHA_MSR_PMON_BOX_FILTER_NNC;
reg1->idx = idx;
}
return 0;
if (unlikely(event->hw.event_base == MSR_SMI_COUNT))
delta = sign_extend64(delta, 31);
- local64_add(now - prev, &event->count);
+ local64_add(delta, &event->count);
}
static void msr_event_start(struct perf_event *event, int flags)
#define ARCH_HAS_RELATIVE_EXTABLE
+#define swap_ex_entry_fixup(a, b, tmp, delta) \
+ do { \
+ (a)->fixup = (b)->fixup + (delta); \
+ (b)->fixup = (tmp).fixup - (delta); \
+ (a)->handler = (b)->handler + (delta); \
+ (b)->handler = (tmp).handler - (delta); \
+ } while (0)
+
extern int fixup_exception(struct pt_regs *regs, int trapnr);
extern bool ex_has_fault_handler(unsigned long ip);
extern int early_fixup_exception(unsigned long *ip);
{
unsigned int eax, ebx, ecx, edx;
- if (c->cpuid_level < 4)
+ if (!IS_ENABLED(CONFIG_SMP) || c->cpuid_level < 4)
return 1;
/* Intel has a non-standard dependency on %ecx for this CPUID level. */
if (config_enabled(CONFIG_X86_64))
sp -= 128;
- if (!onsigstack) {
- /* This is the X/Open sanctioned signal stack switching. */
- if (ka->sa.sa_flags & SA_ONSTACK) {
- if (current->sas_ss_size)
- sp = current->sas_ss_sp + current->sas_ss_size;
- } else if (config_enabled(CONFIG_X86_32) &&
- (regs->ss & 0xffff) != __USER_DS &&
- !(ka->sa.sa_flags & SA_RESTORER) &&
- ka->sa.sa_restorer) {
- /* This is the legacy signal stack switching. */
- sp = (unsigned long) ka->sa.sa_restorer;
- }
+ /* This is the X/Open sanctioned signal stack switching. */
+ if (ka->sa.sa_flags & SA_ONSTACK) {
+ if (sas_ss_flags(sp) == 0)
+ sp = current->sas_ss_sp + current->sas_ss_size;
+ } else if (config_enabled(CONFIG_X86_32) &&
+ !onsigstack &&
+ (regs->ss & 0xffff) != __USER_DS &&
+ !(ka->sa.sa_flags & SA_RESTORER) &&
+ ka->sa.sa_restorer) {
+ /* This is the legacy signal stack switching. */
+ sp = (unsigned long) ka->sa.sa_restorer;
}
if (fpu->fpstate_active) {
* primary cores.
*/
ncpus = boot_cpu_data.x86_max_cores;
+ if (!ncpus) {
+ pr_warn("x86_max_cores == zero !?!?");
+ ncpus = 1;
+ }
+
__max_logical_packages = DIV_ROUND_UP(total_cpus, ncpus);
/*
static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *))
{
+ register void *__sp asm(_ASM_SP);
ulong flags = (ctxt->eflags & EFLAGS_MASK) | X86_EFLAGS_IF;
+
if (!(ctxt->d & ByteOp))
fop += __ffs(ctxt->dst.bytes) * FASTOP_SIZE;
+
asm("push %[flags]; popf; call *%[fastop]; pushf; pop %[flags]\n"
: "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags),
- [fastop]"+S"(fop)
+ [fastop]"+S"(fop), "+r"(__sp)
: "c"(ctxt->src2.val));
+
ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK);
if (!fop) /* exception is returned in fop variable */
return emulate_de(ctxt);
#include "blk.h"
-static bool iovec_gap_to_prv(struct request_queue *q,
- struct iovec *prv, struct iovec *cur)
-{
- unsigned long prev_end;
-
- if (!queue_virt_boundary(q))
- return false;
-
- if (prv->iov_base == NULL && prv->iov_len == 0)
- /* prv is not set - don't check */
- return false;
-
- prev_end = (unsigned long)(prv->iov_base + prv->iov_len);
-
- return (((unsigned long)cur->iov_base & queue_virt_boundary(q)) ||
- prev_end & queue_virt_boundary(q));
-}
-
int blk_rq_append_bio(struct request_queue *q, struct request *rq,
struct bio *bio)
{
struct rq_map_data *map_data,
const struct iov_iter *iter, gfp_t gfp_mask)
{
- struct iovec iov, prv = {.iov_base = NULL, .iov_len = 0};
- bool copy = (q->dma_pad_mask & iter->count) || map_data;
+ bool copy = false;
+ unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
struct bio *bio = NULL;
struct iov_iter i;
int ret;
- if (!iter || !iter->count)
- return -EINVAL;
-
- iov_for_each(iov, i, *iter) {
- unsigned long uaddr = (unsigned long) iov.iov_base;
-
- if (!iov.iov_len)
- return -EINVAL;
-
- /*
- * Keep going so we check length of all segments
- */
- if ((uaddr & queue_dma_alignment(q)) ||
- iovec_gap_to_prv(q, &prv, &iov))
- copy = true;
-
- prv.iov_base = iov.iov_base;
- prv.iov_len = iov.iov_len;
- }
+ if (map_data)
+ copy = true;
+ else if (iov_iter_alignment(iter) & align)
+ copy = true;
+ else if (queue_virt_boundary(q))
+ copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
i = *iter;
do {
config CRYPTO_RSA
tristate "RSA algorithm"
select CRYPTO_AKCIPHER
+ select CRYPTO_MANAGER
select MPILIB
select ASN1
help
struct scatterlist *sg;
sg = walk->sg;
- walk->pg = sg_page(sg);
walk->offset = sg->offset;
+ walk->pg = sg_page(walk->sg) + (walk->offset >> PAGE_SHIFT);
+ walk->offset = offset_in_page(walk->offset);
walk->entrylen = sg->length;
if (walk->entrylen > walk->total)
static int do_test_rsa(struct crypto_akcipher *tfm,
struct akcipher_testvec *vecs)
{
+ char *xbuf[XBUFSIZE];
struct akcipher_request *req;
void *outbuf_enc = NULL;
void *outbuf_dec = NULL;
int err = -ENOMEM;
struct scatterlist src, dst, src_tab[2];
+ if (testmgr_alloc_buf(xbuf))
+ return err;
+
req = akcipher_request_alloc(tfm, GFP_KERNEL);
if (!req)
- return err;
+ goto free_xbuf;
init_completion(&result.completion);
if (!outbuf_enc)
goto free_req;
+ if (WARN_ON(vecs->m_size > PAGE_SIZE))
+ goto free_all;
+
+ memcpy(xbuf[0], vecs->m, vecs->m_size);
+
sg_init_table(src_tab, 2);
- sg_set_buf(&src_tab[0], vecs->m, 8);
- sg_set_buf(&src_tab[1], vecs->m + 8, vecs->m_size - 8);
+ sg_set_buf(&src_tab[0], xbuf[0], 8);
+ sg_set_buf(&src_tab[1], xbuf[0] + 8, vecs->m_size - 8);
sg_init_one(&dst, outbuf_enc, out_len_max);
akcipher_request_set_crypt(req, src_tab, &dst, vecs->m_size,
out_len_max);
goto free_all;
}
/* verify that encrypted message is equal to expected */
- if (memcmp(vecs->c, sg_virt(req->dst), vecs->c_size)) {
+ if (memcmp(vecs->c, outbuf_enc, vecs->c_size)) {
pr_err("alg: rsa: encrypt test failed. Invalid output\n");
err = -EINVAL;
goto free_all;
err = -ENOMEM;
goto free_all;
}
- sg_init_one(&src, vecs->c, vecs->c_size);
+
+ if (WARN_ON(vecs->c_size > PAGE_SIZE))
+ goto free_all;
+
+ memcpy(xbuf[0], vecs->c, vecs->c_size);
+
+ sg_init_one(&src, xbuf[0], vecs->c_size);
sg_init_one(&dst, outbuf_dec, out_len_max);
init_completion(&result.completion);
akcipher_request_set_crypt(req, &src, &dst, vecs->c_size, out_len_max);
kfree(outbuf_enc);
free_req:
akcipher_request_free(req);
+free_xbuf:
+ testmgr_free_buf(xbuf);
return err;
}
If unsure, say N.
+config SATA_AHCI_SEATTLE
+ tristate "AMD Seattle 6.0Gbps AHCI SATA host controller support"
+ depends on ARCH_SEATTLE
+ help
+ This option enables support for AMD Seattle SATA host controller.
+
+ If unsure, say N
+
config SATA_INIC162X
tristate "Initio 162x SATA support (Very Experimental)"
depends on PCI
# non-SFF interface
obj-$(CONFIG_SATA_AHCI) += ahci.o libahci.o
obj-$(CONFIG_SATA_ACARD_AHCI) += acard-ahci.o libahci.o
+obj-$(CONFIG_SATA_AHCI_SEATTLE) += ahci_seattle.o libahci.o libahci_platform.o
obj-$(CONFIG_SATA_AHCI_PLATFORM) += ahci_platform.o libahci.o libahci_platform.o
obj-$(CONFIG_SATA_FSL) += sata_fsl.o
obj-$(CONFIG_SATA_INIC162X) += sata_inic162x.o
if (rc)
return rc;
+ of_property_read_u32(dev->of_node,
+ "ports-implemented", &hpriv->force_port_map);
+
if (of_device_is_compatible(dev->of_node, "hisilicon,hisi-ahci"))
hpriv->flags |= AHCI_HFLAG_NO_FBS | AHCI_HFLAG_NO_NCQ;
--- /dev/null
+/*
+ * AMD Seattle AHCI SATA driver
+ *
+ * Copyright (c) 2015, Advanced Micro Devices
+ * Author: Brijesh Singh <brijesh.singh@amd.com>
+ *
+ * based on the AHCI SATA platform driver by Jeff Garzik and Anton Vorontsov
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pm.h>
+#include <linux/device.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/libata.h>
+#include <linux/ahci_platform.h>
+#include <linux/acpi.h>
+#include <linux/pci_ids.h>
+#include "ahci.h"
+
+/* SGPIO Control Register definition
+ *
+ * Bit Type Description
+ * 31 RW OD7.2 (activity)
+ * 30 RW OD7.1 (locate)
+ * 29 RW OD7.0 (fault)
+ * 28...8 RW OD6.2...OD0.0 (3bits per port, 1 bit per LED)
+ * 7 RO SGPIO feature flag
+ * 6:4 RO Reserved
+ * 3:0 RO Number of ports (0 means no port supported)
+ */
+#define ACTIVITY_BIT_POS(x) (8 + (3 * x))
+#define LOCATE_BIT_POS(x) (ACTIVITY_BIT_POS(x) + 1)
+#define FAULT_BIT_POS(x) (LOCATE_BIT_POS(x) + 1)
+
+#define ACTIVITY_MASK 0x00010000
+#define LOCATE_MASK 0x00080000
+#define FAULT_MASK 0x00400000
+
+#define DRV_NAME "ahci-seattle"
+
+static ssize_t seattle_transmit_led_message(struct ata_port *ap, u32 state,
+ ssize_t size);
+
+struct seattle_plat_data {
+ void __iomem *sgpio_ctrl;
+};
+
+static struct ata_port_operations ahci_port_ops = {
+ .inherits = &ahci_ops,
+};
+
+static const struct ata_port_info ahci_port_info = {
+ .flags = AHCI_FLAG_COMMON,
+ .pio_mask = ATA_PIO4,
+ .udma_mask = ATA_UDMA6,
+ .port_ops = &ahci_port_ops,
+};
+
+static struct ata_port_operations ahci_seattle_ops = {
+ .inherits = &ahci_ops,
+ .transmit_led_message = seattle_transmit_led_message,
+};
+
+static const struct ata_port_info ahci_port_seattle_info = {
+ .flags = AHCI_FLAG_COMMON | ATA_FLAG_EM | ATA_FLAG_SW_ACTIVITY,
+ .link_flags = ATA_LFLAG_SW_ACTIVITY,
+ .pio_mask = ATA_PIO4,
+ .udma_mask = ATA_UDMA6,
+ .port_ops = &ahci_seattle_ops,
+};
+
+static struct scsi_host_template ahci_platform_sht = {
+ AHCI_SHT(DRV_NAME),
+};
+
+static ssize_t seattle_transmit_led_message(struct ata_port *ap, u32 state,
+ ssize_t size)
+{
+ struct ahci_host_priv *hpriv = ap->host->private_data;
+ struct ahci_port_priv *pp = ap->private_data;
+ struct seattle_plat_data *plat_data = hpriv->plat_data;
+ unsigned long flags;
+ int pmp;
+ struct ahci_em_priv *emp;
+ u32 val;
+
+ /* get the slot number from the message */
+ pmp = (state & EM_MSG_LED_PMP_SLOT) >> 8;
+ if (pmp >= EM_MAX_SLOTS)
+ return -EINVAL;
+ emp = &pp->em_priv[pmp];
+
+ val = ioread32(plat_data->sgpio_ctrl);
+ if (state & ACTIVITY_MASK)
+ val |= 1 << ACTIVITY_BIT_POS((ap->port_no));
+ else
+ val &= ~(1 << ACTIVITY_BIT_POS((ap->port_no)));
+
+ if (state & LOCATE_MASK)
+ val |= 1 << LOCATE_BIT_POS((ap->port_no));
+ else
+ val &= ~(1 << LOCATE_BIT_POS((ap->port_no)));
+
+ if (state & FAULT_MASK)
+ val |= 1 << FAULT_BIT_POS((ap->port_no));
+ else
+ val &= ~(1 << FAULT_BIT_POS((ap->port_no)));
+
+ iowrite32(val, plat_data->sgpio_ctrl);
+
+ spin_lock_irqsave(ap->lock, flags);
+
+ /* save off new led state for port/slot */
+ emp->led_state = state;
+
+ spin_unlock_irqrestore(ap->lock, flags);
+
+ return size;
+}
+
+static const struct ata_port_info *ahci_seattle_get_port_info(
+ struct platform_device *pdev, struct ahci_host_priv *hpriv)
+{
+ struct device *dev = &pdev->dev;
+ struct seattle_plat_data *plat_data;
+ u32 val;
+
+ plat_data = devm_kzalloc(dev, sizeof(*plat_data), GFP_KERNEL);
+ if (IS_ERR(plat_data))
+ return &ahci_port_info;
+
+ plat_data->sgpio_ctrl = devm_ioremap_resource(dev,
+ platform_get_resource(pdev, IORESOURCE_MEM, 1));
+ if (IS_ERR(plat_data->sgpio_ctrl))
+ return &ahci_port_info;
+
+ val = ioread32(plat_data->sgpio_ctrl);
+
+ if (!(val & 0xf))
+ return &ahci_port_info;
+
+ hpriv->em_loc = 0;
+ hpriv->em_buf_sz = 4;
+ hpriv->em_msg_type = EM_MSG_TYPE_LED;
+ hpriv->plat_data = plat_data;
+
+ dev_info(dev, "SGPIO LED control is enabled.\n");
+ return &ahci_port_seattle_info;
+}
+
+static int ahci_seattle_probe(struct platform_device *pdev)
+{
+ int rc;
+ struct ahci_host_priv *hpriv;
+
+ hpriv = ahci_platform_get_resources(pdev);
+ if (IS_ERR(hpriv))
+ return PTR_ERR(hpriv);
+
+ rc = ahci_platform_enable_resources(hpriv);
+ if (rc)
+ return rc;
+
+ rc = ahci_platform_init_host(pdev, hpriv,
+ ahci_seattle_get_port_info(pdev, hpriv),
+ &ahci_platform_sht);
+ if (rc)
+ goto disable_resources;
+
+ return 0;
+disable_resources:
+ ahci_platform_disable_resources(hpriv);
+ return rc;
+}
+
+static SIMPLE_DEV_PM_OPS(ahci_pm_ops, ahci_platform_suspend,
+ ahci_platform_resume);
+
+static const struct acpi_device_id ahci_acpi_match[] = {
+ { "AMDI0600", 0 },
+ {}
+};
+MODULE_DEVICE_TABLE(acpi, ahci_acpi_match);
+
+static struct platform_driver ahci_seattle_driver = {
+ .probe = ahci_seattle_probe,
+ .remove = ata_platform_remove_one,
+ .driver = {
+ .name = DRV_NAME,
+ .acpi_match_table = ahci_acpi_match,
+ .pm = &ahci_pm_ops,
+ },
+};
+module_platform_driver(ahci_seattle_driver);
+
+MODULE_DESCRIPTION("Seattle AHCI SATA platform driver");
+MODULE_AUTHOR("Brijesh Singh <brijesh.singh@amd.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:" DRV_NAME);
dev_info(dev, "forcing port_map 0x%x -> 0x%x\n",
port_map, hpriv->force_port_map);
port_map = hpriv->force_port_map;
+ hpriv->saved_port_map = port_map;
}
if (hpriv->mask_port_map) {
#ifndef _REGMAP_INTERNAL_H
#define _REGMAP_INTERNAL_H
+#include <linux/device.h>
#include <linux/regmap.h>
#include <linux/fs.h>
#include <linux/list.h>
#include <linux/regmap.h>
#include <linux/slab.h>
+#include "internal.h"
+
struct regmap_mmio_context {
void __iomem *regs;
unsigned val_bytes;
.reg_write = regmap_mmio_write,
.reg_read = regmap_mmio_read,
.free_context = regmap_mmio_free_context,
+ .val_format_endian_default = REGMAP_ENDIAN_LITTLE,
};
static struct regmap_mmio_context *regmap_mmio_gen_context(struct device *dev,
ctx->val_bytes = config->val_bits / 8;
ctx->clk = ERR_PTR(-ENODEV);
- switch (config->reg_format_endian) {
+ switch (regmap_get_val_endian(dev, ®map_mmio, config)) {
case REGMAP_ENDIAN_DEFAULT:
case REGMAP_ENDIAN_LITTLE:
#ifdef __LITTLE_ENDIAN
while (val_size) {
len = min_t(size_t, val_size, 8);
- err = spmi_ext_register_readl(context, addr, val, val_size);
+ err = spmi_ext_register_readl(context, addr, val, len);
if (err)
goto err_out;
uint32_t vf_mask);
void adf_enable_pf2vf_interrupts(struct adf_accel_dev *accel_dev);
void adf_disable_pf2vf_interrupts(struct adf_accel_dev *accel_dev);
+int adf_init_pf_wq(void);
+void adf_exit_pf_wq(void);
#else
static inline int adf_sriov_configure(struct pci_dev *pdev, int numvfs)
{
static inline void adf_disable_pf2vf_interrupts(struct adf_accel_dev *accel_dev)
{
}
+
+static inline int adf_init_pf_wq(void)
+{
+ return 0;
+}
+
+static inline void adf_exit_pf_wq(void)
+{
+}
#endif
#endif
if (adf_init_aer())
goto err_aer;
+ if (adf_init_pf_wq())
+ goto err_pf_wq;
+
if (qat_crypto_register())
goto err_crypto_register;
return 0;
err_crypto_register:
+ adf_exit_pf_wq();
+err_pf_wq:
adf_exit_aer();
err_aer:
adf_chr_drv_destroy();
{
adf_chr_drv_destroy();
adf_exit_aer();
+ adf_exit_pf_wq();
qat_crypto_unregister();
adf_clean_vf_map(false);
mutex_destroy(&adf_ctl_lock);
int i;
u32 reg;
- /* Workqueue for PF2VF responses */
- pf2vf_resp_wq = create_workqueue("qat_pf2vf_resp_wq");
- if (!pf2vf_resp_wq)
- return -ENOMEM;
-
for (i = 0, vf_info = accel_dev->pf.vf_info; i < totalvfs;
i++, vf_info++) {
/* This ptr will be populated when VFs will be created */
kfree(accel_dev->pf.vf_info);
accel_dev->pf.vf_info = NULL;
-
- if (pf2vf_resp_wq) {
- destroy_workqueue(pf2vf_resp_wq);
- pf2vf_resp_wq = NULL;
- }
}
EXPORT_SYMBOL_GPL(adf_disable_sriov);
return numvfs;
}
EXPORT_SYMBOL_GPL(adf_sriov_configure);
+
+int __init adf_init_pf_wq(void)
+{
+ /* Workqueue for PF2VF responses */
+ pf2vf_resp_wq = create_workqueue("qat_pf2vf_resp_wq");
+
+ return !pf2vf_resp_wq ? -ENOMEM : 0;
+}
+
+void adf_exit_pf_wq(void)
+{
+ if (pf2vf_resp_wq) {
+ destroy_workqueue(pf2vf_resp_wq);
+ pf2vf_resp_wq = NULL;
+ }
+}
}
}
} else {
- for (lane_num = 1; lane_num <= max_lane_num; lane_num <<= 1) {
- for (i = 0; i < ARRAY_SIZE(link_rates) && link_rates[i] <= max_link_rate; i++) {
+ for (i = 0; i < ARRAY_SIZE(link_rates) && link_rates[i] <= max_link_rate; i++) {
+ for (lane_num = 1; lane_num <= max_lane_num; lane_num <<= 1) {
max_pix_clock = (lane_num * link_rates[i] * 8) / bpp;
if (max_pix_clock >= pix_clock) {
*dp_lanes = lane_num;
intel_panel_info(m, &intel_connector->panel);
}
-static void intel_dp_mst_info(struct seq_file *m,
- struct intel_connector *intel_connector)
-{
- struct intel_encoder *intel_encoder = intel_connector->encoder;
- struct intel_dp_mst_encoder *intel_mst =
- enc_to_mst(&intel_encoder->base);
- struct intel_digital_port *intel_dig_port = intel_mst->primary;
- struct intel_dp *intel_dp = &intel_dig_port->dp;
- bool has_audio = drm_dp_mst_port_has_audio(&intel_dp->mst_mgr,
- intel_connector->port);
-
- seq_printf(m, "\taudio support: %s\n", yesno(has_audio));
-}
-
static void intel_hdmi_info(struct seq_file *m,
struct intel_connector *intel_connector)
{
intel_hdmi_info(m, intel_connector);
else if (intel_encoder->type == INTEL_OUTPUT_LVDS)
intel_lvds_info(m, intel_connector);
- else if (intel_encoder->type == INTEL_OUTPUT_DP_MST)
- intel_dp_mst_info(m, intel_connector);
}
seq_printf(m, "\tmodes:\n");
#define TRANS_CLK_SEL_DISABLED (0x0<<29)
#define TRANS_CLK_SEL_PORT(x) (((x)+1)<<29)
+#define CDCLK_FREQ _MMIO(0x46200)
+
#define _TRANSA_MSA_MISC 0x60410
#define _TRANSB_MSA_MISC 0x61410
#define _TRANSC_MSA_MISC 0x62410
tmp |= AUD_CONFIG_N_PROG_ENABLE;
tmp &= ~AUD_CONFIG_UPPER_N_MASK;
tmp &= ~AUD_CONFIG_LOWER_N_MASK;
- if (intel_pipe_has_type(intel_crtc, INTEL_OUTPUT_DISPLAYPORT) ||
- intel_pipe_has_type(intel_crtc, INTEL_OUTPUT_DP_MST))
+ if (intel_pipe_has_type(intel_crtc, INTEL_OUTPUT_DISPLAYPORT))
tmp |= AUD_CONFIG_N_VALUE_INDEX;
I915_WRITE(HSW_AUD_CFG(pipe), tmp);
tmp &= ~AUD_CONFIG_N_VALUE_INDEX;
tmp &= ~AUD_CONFIG_N_PROG_ENABLE;
tmp &= ~AUD_CONFIG_PIXEL_CLOCK_HDMI_MASK;
- if (intel_pipe_has_type(intel_crtc, INTEL_OUTPUT_DISPLAYPORT) ||
- intel_pipe_has_type(intel_crtc, INTEL_OUTPUT_DP_MST))
+ if (intel_pipe_has_type(intel_crtc, INTEL_OUTPUT_DISPLAYPORT))
tmp |= AUD_CONFIG_N_VALUE_INDEX;
else
tmp |= audio_config_hdmi_pixel_clock(adjusted_mode);
/* ELD Conn_Type */
connector->eld[5] &= ~(3 << 2);
- if (intel_pipe_has_type(crtc, INTEL_OUTPUT_DISPLAYPORT) ||
- intel_pipe_has_type(crtc, INTEL_OUTPUT_DP_MST))
+ if (intel_pipe_has_type(crtc, INTEL_OUTPUT_DISPLAYPORT))
connector->eld[5] |= (1 << 2);
connector->eld[6] = drm_av_sync_delay(connector, adjusted_mode) / 2;
pipe_config->has_pch_encoder = true;
/* LPT FDI RX only supports 8bpc. */
- if (HAS_PCH_LPT(dev))
+ if (HAS_PCH_LPT(dev)) {
+ if (pipe_config->bw_constrained && pipe_config->pipe_bpp < 24) {
+ DRM_DEBUG_KMS("LPT only supports 24bpp\n");
+ return false;
+ }
+
pipe_config->pipe_bpp = 24;
+ }
/* FDI must always be 2.7 GHz */
if (HAS_DDI(dev)) {
I915_WRITE(FDI_RX_CTL(PIPE_A), val);
}
-bool intel_ddi_is_audio_enabled(struct drm_i915_private *dev_priv,
- struct intel_crtc *intel_crtc)
-{
- u32 temp;
-
- if (intel_display_power_get_if_enabled(dev_priv, POWER_DOMAIN_AUDIO)) {
- temp = I915_READ(HSW_AUD_PIN_ELD_CP_VLD);
-
- intel_display_power_put(dev_priv, POWER_DOMAIN_AUDIO);
-
- if (temp & AUDIO_OUTPUT_ENABLE(intel_crtc->pipe))
- return true;
- }
-
- return false;
-}
-
void intel_ddi_get_config(struct intel_encoder *encoder,
struct intel_crtc_state *pipe_config)
{
break;
}
- pipe_config->has_audio =
- intel_ddi_is_audio_enabled(dev_priv, intel_crtc);
+ if (intel_display_power_is_enabled(dev_priv, POWER_DOMAIN_AUDIO)) {
+ temp = I915_READ(HSW_AUD_PIN_ELD_CP_VLD);
+ if (temp & AUDIO_OUTPUT_ENABLE(intel_crtc->pipe))
+ pipe_config->has_audio = true;
+ }
if (encoder->type == INTEL_OUTPUT_EDP && dev_priv->vbt.edp_bpp &&
pipe_config->pipe_bpp > dev_priv->vbt.edp_bpp) {
pipe_config->gmch_pfit.control = tmp;
pipe_config->gmch_pfit.pgm_ratios = I915_READ(PFIT_PGM_RATIOS);
- if (INTEL_INFO(dev)->gen < 5)
- pipe_config->gmch_pfit.lvds_border_bits =
- I915_READ(LVDS) & LVDS_BORDER_ENABLE;
}
static void vlv_crtc_clock_get(struct intel_crtc *crtc,
sandybridge_pcode_write(dev_priv, HSW_PCODE_DE_WRITE_FREQ_REQ, data);
mutex_unlock(&dev_priv->rps.hw_lock);
+ I915_WRITE(CDCLK_FREQ, DIV_ROUND_CLOSEST(cdclk, 1000) - 1);
+
intel_update_cdclk(dev);
WARN(cdclk != dev_priv->cdclk_freq,
return false;
}
- if (drm_dp_mst_port_has_audio(&intel_dp->mst_mgr, found->port))
- pipe_config->has_audio = true;
mst_pbn = drm_dp_calc_pbn_mode(adjusted_mode->crtc_clock, bpp);
pipe_config->pbn = mst_pbn;
struct intel_dp_mst_encoder *intel_mst = enc_to_mst(&encoder->base);
struct intel_digital_port *intel_dig_port = intel_mst->primary;
struct intel_dp *intel_dp = &intel_dig_port->dp;
- struct drm_device *dev = encoder->base.dev;
- struct drm_i915_private *dev_priv = dev->dev_private;
- struct drm_crtc *crtc = encoder->base.crtc;
- struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-
int ret;
DRM_DEBUG_KMS("%d\n", intel_dp->active_mst_links);
if (ret) {
DRM_ERROR("failed to update payload %d\n", ret);
}
- if (intel_crtc->config->has_audio) {
- intel_audio_codec_disable(encoder);
- intel_display_power_put(dev_priv, POWER_DOMAIN_AUDIO);
- }
}
static void intel_mst_post_disable_dp(struct intel_encoder *encoder)
struct intel_dp *intel_dp = &intel_dig_port->dp;
struct drm_device *dev = intel_dig_port->base.base.dev;
struct drm_i915_private *dev_priv = dev->dev_private;
- struct intel_crtc *crtc = to_intel_crtc(encoder->base.crtc);
enum port port = intel_dig_port->port;
int ret;
ret = drm_dp_check_act_status(&intel_dp->mst_mgr);
ret = drm_dp_update_payload_part2(&intel_dp->mst_mgr);
-
- if (crtc->config->has_audio) {
- DRM_DEBUG_DRIVER("Enabling DP audio on pipe %c\n",
- pipe_name(crtc->pipe));
- intel_display_power_get(dev_priv, POWER_DOMAIN_AUDIO);
- intel_audio_codec_enable(encoder);
- }
}
static bool intel_dp_mst_enc_get_hw_state(struct intel_encoder *encoder,
pipe_config->has_dp_encoder = true;
- pipe_config->has_audio =
- intel_ddi_is_audio_enabled(dev_priv, crtc);
-
temp = I915_READ(TRANS_DDI_FUNC_CTL(cpu_transcoder));
if (temp & TRANS_DDI_PHSYNC)
flags |= DRM_MODE_FLAG_PHSYNC;
void intel_ddi_prepare_link_retrain(struct intel_dp *intel_dp);
bool intel_ddi_connector_get_hw_state(struct intel_connector *intel_connector);
void intel_ddi_fdi_disable(struct drm_crtc *crtc);
-bool intel_ddi_is_audio_enabled(struct drm_i915_private *dev_priv,
- struct intel_crtc *intel_crtc);
void intel_ddi_get_config(struct intel_encoder *encoder,
struct intel_crtc_state *pipe_config);
struct intel_encoder *
pipe_config->base.adjusted_mode.flags |= flags;
+ if (INTEL_INFO(dev)->gen < 5)
+ pipe_config->gmch_pfit.lvds_border_bits =
+ tmp & LVDS_BORDER_ENABLE;
+
/* gen2/3 store dither state in pfit control, needs to match */
if (INTEL_INFO(dev)->gen < 4) {
tmp = I915_READ(PFIT_CONTROL);
misccpctl = I915_READ(GEN7_MISCCPCTL);
I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
I915_WRITE(GEN8_L3SQCREG1, BDW_WA_L3SQCREG1_DEFAULT);
+ /*
+ * Wait at least 100 clocks before re-enabling clock gating. See
+ * the definition of L3SQCREG1 in BSpec.
+ */
+ POSTING_READ(GEN8_L3SQCREG1);
+ udelay(1);
I915_WRITE(GEN7_MISCCPCTL, misccpctl);
/*
static int radeon_get_shared_dp_ppll(struct drm_crtc *crtc)
{
struct drm_device *dev = crtc->dev;
+ struct radeon_device *rdev = dev->dev_private;
struct drm_crtc *test_crtc;
struct radeon_crtc *test_radeon_crtc;
test_radeon_crtc = to_radeon_crtc(test_crtc);
if (test_radeon_crtc->encoder &&
ENCODER_MODE_IS_DP(atombios_get_encoder_mode(test_radeon_crtc->encoder))) {
+ /* PPLL2 is exclusive to UNIPHYA on DCE61 */
+ if (ASIC_IS_DCE61(rdev) && !ASIC_IS_DCE8(rdev) &&
+ test_radeon_crtc->pll_id == ATOM_PPLL2)
+ continue;
/* for DP use the same PLL for all */
if (test_radeon_crtc->pll_id != ATOM_PPLL_INVALID)
return test_radeon_crtc->pll_id;
{
struct radeon_crtc *radeon_crtc = to_radeon_crtc(crtc);
struct drm_device *dev = crtc->dev;
+ struct radeon_device *rdev = dev->dev_private;
struct drm_crtc *test_crtc;
struct radeon_crtc *test_radeon_crtc;
u32 adjusted_clock, test_adjusted_clock;
test_radeon_crtc = to_radeon_crtc(test_crtc);
if (test_radeon_crtc->encoder &&
!ENCODER_MODE_IS_DP(atombios_get_encoder_mode(test_radeon_crtc->encoder))) {
+ /* PPLL2 is exclusive to UNIPHYA on DCE61 */
+ if (ASIC_IS_DCE61(rdev) && !ASIC_IS_DCE8(rdev) &&
+ test_radeon_crtc->pll_id == ATOM_PPLL2)
+ continue;
/* check if we are already driving this connector with another crtc */
if (test_radeon_crtc->connector == radeon_crtc->connector) {
/* if we are, return that pll */
}
}
} else {
- for (lane_num = 1; lane_num <= max_lane_num; lane_num <<= 1) {
- for (i = 0; i < ARRAY_SIZE(link_rates) && link_rates[i] <= max_link_rate; i++) {
+ for (i = 0; i < ARRAY_SIZE(link_rates) && link_rates[i] <= max_link_rate; i++) {
+ for (lane_num = 1; lane_num <= max_lane_num; lane_num <<= 1) {
max_pix_clock = (lane_num * link_rates[i] * 8) / bpp;
if (max_pix_clock >= pix_clock) {
*dp_lanes = lane_num;
tmp &= AUX_HPD_SEL(0x7);
tmp |= AUX_HPD_SEL(chan->rec.hpd);
- tmp |= AUX_EN | AUX_LS_READ_EN;
+ tmp |= AUX_EN | AUX_LS_READ_EN | AUX_HPD_DISCON(0x1);
WREG32(AUX_CONTROL + aux_offset[instance], tmp);
* there is room for the producer to send the pending packet.
*/
-static bool hv_need_to_signal_on_read(u32 prev_write_sz,
- struct hv_ring_buffer_info *rbi)
+static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
{
u32 cur_write_sz;
u32 r_size;
- u32 write_loc = rbi->ring_buffer->write_index;
+ u32 write_loc;
u32 read_loc = rbi->ring_buffer->read_index;
- u32 pending_sz = rbi->ring_buffer->pending_send_sz;
+ u32 pending_sz;
+ /*
+ * Issue a full memory barrier before making the signaling decision.
+ * Here is the reason for having this barrier:
+ * If the reading of the pend_sz (in this function)
+ * were to be reordered and read before we commit the new read
+ * index (in the calling function) we could
+ * have a problem. If the host were to set the pending_sz after we
+ * have sampled pending_sz and go to sleep before we commit the
+ * read index, we could miss sending the interrupt. Issue a full
+ * memory barrier to address this.
+ */
+ mb();
+
+ pending_sz = rbi->ring_buffer->pending_send_sz;
+ write_loc = rbi->ring_buffer->write_index;
/* If the other end is not blocked on write don't bother. */
if (pending_sz == 0)
return false;
cur_write_sz = write_loc >= read_loc ? r_size - (write_loc - read_loc) :
read_loc - write_loc;
- if ((prev_write_sz < pending_sz) && (cur_write_sz >= pending_sz))
+ if (cur_write_sz >= pending_sz)
return true;
return false;
/* Update the read index */
hv_set_next_read_location(inring_info, next_read_location);
- *signal = hv_need_to_signal_on_read(bytes_avail_towrite, inring_info);
+ *signal = hv_need_to_signal_on_read(inring_info);
return ret;
}
if (ret)
goto vref_disable;
+ platform_set_drvdata(pdev, indio_dev);
+
ret = iio_device_register(indio_dev);
if (ret < 0)
goto per_clk_disable_unprepare;
return 0;
}
+static const char *inv_mpu_match_acpi_device(struct device *dev, int *chip_id)
+{
+ const struct acpi_device_id *id;
+
+ id = acpi_match_device(dev->driver->acpi_match_table, dev);
+ if (!id)
+ return NULL;
+
+ *chip_id = (int)id->driver_data;
+
+ return dev_name(dev);
+}
+
/**
* inv_mpu_probe() - probe function.
* @client: i2c client.
const struct i2c_device_id *id)
{
struct inv_mpu6050_state *st;
- int result;
- const char *name = id ? id->name : NULL;
+ int result, chip_type;
struct regmap *regmap;
+ const char *name;
if (!i2c_check_functionality(client->adapter,
I2C_FUNC_SMBUS_I2C_BLOCK))
return -EOPNOTSUPP;
+ if (id) {
+ chip_type = (int)id->driver_data;
+ name = id->name;
+ } else if (ACPI_HANDLE(&client->dev)) {
+ name = inv_mpu_match_acpi_device(&client->dev, &chip_type);
+ if (!name)
+ return -ENODEV;
+ } else {
+ return -ENOSYS;
+ }
+
regmap = devm_regmap_init_i2c(client, &inv_mpu_regmap_config);
if (IS_ERR(regmap)) {
dev_err(&client->dev, "Failed to register i2c regmap %d\n",
}
result = inv_mpu_core_probe(regmap, client->irq, name,
- NULL, id->driver_data);
+ NULL, chip_type);
if (result < 0)
return result;
struct regmap *regmap;
const struct spi_device_id *id = spi_get_device_id(spi);
const char *name = id ? id->name : NULL;
+ const int chip_type = id ? id->driver_data : 0;
regmap = devm_regmap_init_spi(spi, &inv_mpu_regmap_config);
if (IS_ERR(regmap)) {
}
return inv_mpu_core_probe(regmap, spi->irq, name,
- inv_mpu_i2c_disable, id->driver_data);
+ inv_mpu_i2c_disable, chip_type);
}
static int inv_mpu_remove(struct spi_device *spi)
int rc;
int irq;
+ init_waitqueue_head(&data->data_ready_queue);
+ clear_bit(0, &data->flags);
if (client->irq)
irq = client->irq;
else
return rc;
}
- init_waitqueue_head(&data->data_ready_queue);
- clear_bit(0, &data->flags);
data->eoc_irq = irq;
return rc;
int eoc_gpio;
int err;
const char *name = NULL;
- enum asahi_compass_chipset chipset;
+ enum asahi_compass_chipset chipset = AK_MAX_TYPE;
/* Grab and set up the supplied GPIO. */
if (client->dev.platform_data)
struct Scsi_Host *shost;
struct iser_conn *iser_conn = NULL;
struct ib_conn *ib_conn;
+ u32 max_fr_sectors;
u16 max_cmds;
shost = iscsi_host_alloc(&iscsi_iser_sht, 0, 0);
iser_conn = ep->dd_data;
max_cmds = iser_conn->max_cmds;
shost->sg_tablesize = iser_conn->scsi_sg_tablesize;
- shost->max_sectors = iser_conn->scsi_max_sectors;
mutex_lock(&iser_conn->state_mutex);
if (iser_conn->state != ISER_CONN_UP) {
*/
shost->sg_tablesize = min_t(unsigned short, shost->sg_tablesize,
ib_conn->device->ib_device->attrs.max_fast_reg_page_list_len);
- shost->max_sectors = min_t(unsigned int,
- 1024, (shost->sg_tablesize * PAGE_SIZE) >> 9);
if (iscsi_host_add(shost,
ib_conn->device->ib_device->dma_device)) {
goto free_host;
}
+ /*
+ * FRs or FMRs can only map up to a (device) page per entry, but if the
+ * first entry is misaligned we'll end up using using two entries
+ * (head and tail) for a single page worth data, so we have to drop
+ * one segment from the calculation.
+ */
+ max_fr_sectors = ((shost->sg_tablesize - 1) * PAGE_SIZE) >> 9;
+ shost->max_sectors = min(iser_max_sectors, max_fr_sectors);
+
if (cmds_max > max_cmds) {
iser_info("cmds_max changed from %u to %u\n",
cmds_max, max_cmds);
.queuecommand = iscsi_queuecommand,
.change_queue_depth = scsi_change_queue_depth,
.sg_tablesize = ISCSI_ISER_DEF_SG_TABLESIZE,
- .max_sectors = ISER_DEF_MAX_SECTORS,
.cmd_per_lun = ISER_DEF_CMD_PER_LUN,
.eh_abort_handler = iscsi_eh_abort,
.eh_device_reset_handler= iscsi_eh_device_reset,
struct max8997_dev *iodev = dev_get_drvdata(pdev->dev.parent);
const struct max8997_platform_data *pdata =
dev_get_platdata(iodev->dev);
- const struct max8997_haptic_platform_data *haptic_pdata =
- pdata->haptic_pdata;
+ const struct max8997_haptic_platform_data *haptic_pdata = NULL;
struct max8997_haptic *chip;
struct input_dev *input_dev;
int error;
+ if (pdata)
+ haptic_pdata = pdata->haptic_pdata;
+
if (!haptic_pdata) {
dev_err(&pdev->dev, "no haptic platform data\n");
return -EINVAL;
int vddvibr_uV = 0;
int error;
+ of_node_get(twl6040_core_dev->of_node);
twl6040_core_node = of_find_node_by_name(twl6040_core_dev->of_node,
"vibra");
if (!twl6040_core_node) {
* BYD TouchPad PS/2 mouse driver
*
* Copyright (C) 2015 Chris Diamand <chris@diamand.org>
+ * Copyright (C) 2015 Richard Pospesel
+ * Copyright (C) 2015 Tai Chi Minh Ralph Eastwood
+ * Copyright (C) 2015 Martin Wimpress
+ * Copyright (C) 2015 Jay Kuri
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
}
EXPORT_SYMBOL_GPL(media_device_find_devres);
+#if IS_ENABLED(CONFIG_PCI)
void media_device_pci_init(struct media_device *mdev,
struct pci_dev *pci_dev,
const char *name)
{
-#ifdef CONFIG_PCI
mdev->dev = &pci_dev->dev;
if (name)
mdev->driver_version = LINUX_VERSION_CODE;
media_device_init(mdev);
-#endif
}
EXPORT_SYMBOL_GPL(media_device_pci_init);
+#endif
+#if IS_ENABLED(CONFIG_USB)
void __media_device_usb_init(struct media_device *mdev,
struct usb_device *udev,
const char *board_name,
const char *driver_name)
{
-#ifdef CONFIG_USB
mdev->dev = &udev->dev;
if (driver_name)
mdev->driver_version = LINUX_VERSION_CODE;
media_device_init(mdev);
-#endif
}
EXPORT_SYMBOL_GPL(__media_device_usb_init);
+#endif
#endif /* CONFIG_MEDIA_CONTROLLER */
platform_set_drvdata(pdev, fmd);
- /* Protect the media graph while we're registering entities */
- mutex_lock(&fmd->media_dev.graph_mutex);
-
ret = fimc_md_register_platform_entities(fmd, dev->of_node);
- if (ret) {
- mutex_unlock(&fmd->media_dev.graph_mutex);
+ if (ret)
goto err_clk;
- }
ret = fimc_md_register_sensor_entities(fmd);
- if (ret) {
- mutex_unlock(&fmd->media_dev.graph_mutex);
+ if (ret)
goto err_m_ent;
- }
-
- mutex_unlock(&fmd->media_dev.graph_mutex);
ret = device_create_file(&pdev->dev, &dev_attr_subdev_conf_mode);
if (ret)
if (ret < 0)
goto err_sens;
- mutex_lock(&camif->media_dev.graph_mutex);
-
ret = v4l2_device_register_subdev_nodes(&camif->v4l2_dev);
if (ret < 0)
- goto err_unlock;
+ goto err_sens;
ret = camif_register_video_nodes(camif);
if (ret < 0)
- goto err_unlock;
+ goto err_sens;
ret = camif_create_media_links(camif);
if (ret < 0)
- goto err_unlock;
-
- mutex_unlock(&camif->media_dev.graph_mutex);
+ goto err_sens;
ret = media_device_register(&camif->media_dev);
if (ret < 0)
pm_runtime_put(dev);
return 0;
-err_unlock:
- mutex_unlock(&camif->media_dev.graph_mutex);
err_sens:
v4l2_device_unregister(&camif->v4l2_dev);
media_device_unregister(&camif->media_dev);
return 0;
}
-static int __verify_planes_array_core(struct vb2_buffer *vb, const void *pb)
-{
- return __verify_planes_array(vb, pb);
-}
-
/**
* __verify_length() - Verify that the bytesused value for each plane fits in
* the plane length and that the data offset doesn't exceed the bytesused value.
}
static const struct vb2_buf_ops v4l2_buf_ops = {
- .verify_planes_array = __verify_planes_array_core,
.fill_user_buffer = __fill_v4l2_buffer,
.fill_vb2_buffer = __fill_vb2_buffer,
.copy_timestamp = __copy_timestamp,
ret = -EFAULT;
goto free_ret;
}
+ /* Ensure desc has not changed between the two reads */
+ if (memcmp(&dd, dd_config, sizeof(dd))) {
+ ret = -EINVAL;
+ goto free_ret;
+ }
mutex_lock(&vdev->vdev_mutex);
mutex_lock(&vi->vop_mutex);
ret = vop_virtio_add_device(vdev, dd_config);
static void xgene_cle_dbptr_to_hw(struct xgene_enet_pdata *pdata,
struct xgene_cle_dbptr *dbptr, u32 *buf)
{
+ buf[0] = SET_VAL(CLE_DROP, dbptr->drop);
buf[4] = SET_VAL(CLE_FPSEL, dbptr->fpsel) |
SET_VAL(CLE_DSTQIDL, dbptr->dstqid);
.branch = {
{
/* IPV4 */
- .valid = 0,
+ .valid = 1,
.next_packet_pointer = 22,
.jump_bw = JMP_FW,
.jump_rel = JMP_ABS,
.next_node = PKT_PROT_NODE,
.next_branch = 0,
.data = 0x8,
- .mask = 0xffff
+ .mask = 0x0
},
{
.valid = 0,
.next_node = RSS_IPV4_TCP_NODE,
.next_branch = 0,
.data = 0x0600,
- .mask = 0xffff
+ .mask = 0x00ff
},
{
/* UDP */
.next_node = RSS_IPV4_UDP_NODE,
.next_branch = 0,
.data = 0x1100,
- .mask = 0xffff
+ .mask = 0x00ff
},
{
.valid = 0,
{
/* TCP DST Port */
.valid = 0,
- .next_packet_pointer = 256,
+ .next_packet_pointer = 258,
.jump_bw = JMP_FW,
.jump_rel = JMP_ABS,
.operation = EQT,
#define CLE_TYPE_POS 0
#define CLE_TYPE_LEN 2
+#define CLE_DROP_POS 28
+#define CLE_DROP_LEN 1
#define CLE_DSTQIDL_POS 25
#define CLE_DSTQIDL_LEN 7
#define CLE_DSTQIDH_POS 0
struct xgene_enet_pdata *pdata,
enum xgene_enet_err_code status)
{
- struct rtnl_link_stats64 *stats = &pdata->stats;
-
switch (status) {
case INGRESS_CRC:
- stats->rx_crc_errors++;
+ ring->rx_crc_errors++;
+ ring->rx_dropped++;
break;
case INGRESS_CHECKSUM:
case INGRESS_CHECKSUM_COMPUTE:
- stats->rx_errors++;
+ ring->rx_errors++;
+ ring->rx_dropped++;
break;
case INGRESS_TRUNC_FRAME:
- stats->rx_frame_errors++;
+ ring->rx_frame_errors++;
+ ring->rx_dropped++;
break;
case INGRESS_PKT_LEN:
- stats->rx_length_errors++;
+ ring->rx_length_errors++;
+ ring->rx_dropped++;
break;
case INGRESS_PKT_UNDER:
- stats->rx_frame_errors++;
+ ring->rx_frame_errors++;
+ ring->rx_dropped++;
break;
case INGRESS_FIFO_OVERRUN:
- stats->rx_fifo_errors++;
+ ring->rx_fifo_errors++;
break;
default:
break;
#define RINGADDRL_POS 5
#define RINGADDRL_LEN 27
#define RINGADDRH_POS 0
-#define RINGADDRH_LEN 6
+#define RINGADDRH_LEN 7
#define RINGSIZE_POS 23
#define RINGSIZE_LEN 3
#define RINGTYPE_POS 19
#define RINGMODE_POS 20
#define RINGMODE_LEN 3
#define RECOMTIMEOUTL_POS 28
-#define RECOMTIMEOUTL_LEN 3
+#define RECOMTIMEOUTL_LEN 4
#define RECOMTIMEOUTH_POS 0
-#define RECOMTIMEOUTH_LEN 2
+#define RECOMTIMEOUTH_LEN 3
#define NUMMSGSINQ_POS 1
#define NUMMSGSINQ_LEN 16
#define ACCEPTLERR BIT(19)
#define USERINFO_LEN 32
#define FPQNUM_POS 32
#define FPQNUM_LEN 12
+#define ELERR_POS 46
+#define ELERR_LEN 2
#define NV_POS 50
#define NV_LEN 1
#define LL_POS 51
skb_tx_timestamp(skb);
- pdata->stats.tx_packets++;
- pdata->stats.tx_bytes += skb->len;
+ tx_ring->tx_packets++;
+ tx_ring->tx_bytes += skb->len;
pdata->ring_ops->wr_cmd(tx_ring, count);
return NETDEV_TX_OK;
skb = buf_pool->rx_skb[skb_index];
/* checking for error */
- status = GET_VAL(LERR, le64_to_cpu(raw_desc->m0));
+ status = (GET_VAL(ELERR, le64_to_cpu(raw_desc->m0)) << LERR_LEN) ||
+ GET_VAL(LERR, le64_to_cpu(raw_desc->m0));
if (unlikely(status > 2)) {
dev_kfree_skb_any(skb);
xgene_enet_parse_error(rx_ring, netdev_priv(rx_ring->ndev),
status);
- pdata->stats.rx_dropped++;
ret = -EIO;
goto out;
}
xgene_enet_skip_csum(skb);
}
- pdata->stats.rx_packets++;
- pdata->stats.rx_bytes += datalen;
+ rx_ring->rx_packets++;
+ rx_ring->rx_bytes += datalen;
napi_gro_receive(&rx_ring->napi, skb);
out:
if (--rx_ring->nbufpool == 0) {
ring = pdata->rx_ring[i];
irq_set_status_flags(ring->irq, IRQ_DISABLE_UNLAZY);
ret = devm_request_irq(dev, ring->irq, xgene_enet_rx_irq,
- IRQF_SHARED, ring->irq_name, ring);
+ 0, ring->irq_name, ring);
if (ret) {
netdev_err(ndev, "Failed to request irq %s\n",
ring->irq_name);
ring = pdata->tx_ring[i]->cp_ring;
irq_set_status_flags(ring->irq, IRQ_DISABLE_UNLAZY);
ret = devm_request_irq(dev, ring->irq, xgene_enet_rx_irq,
- IRQF_SHARED, ring->irq_name, ring);
+ 0, ring->irq_name, ring);
if (ret) {
netdev_err(ndev, "Failed to request irq %s\n",
ring->irq_name);
{
struct xgene_enet_pdata *pdata = netdev_priv(ndev);
struct rtnl_link_stats64 *stats = &pdata->stats;
+ struct xgene_enet_desc_ring *ring;
+ int i;
- stats->rx_errors += stats->rx_length_errors +
- stats->rx_crc_errors +
- stats->rx_frame_errors +
- stats->rx_fifo_errors;
- memcpy(storage, &pdata->stats, sizeof(struct rtnl_link_stats64));
+ memset(stats, 0, sizeof(struct rtnl_link_stats64));
+ for (i = 0; i < pdata->txq_cnt; i++) {
+ ring = pdata->tx_ring[i];
+ if (ring) {
+ stats->tx_packets += ring->tx_packets;
+ stats->tx_bytes += ring->tx_bytes;
+ }
+ }
+
+ for (i = 0; i < pdata->rxq_cnt; i++) {
+ ring = pdata->rx_ring[i];
+ if (ring) {
+ stats->rx_packets += ring->rx_packets;
+ stats->rx_bytes += ring->rx_bytes;
+ stats->rx_errors += ring->rx_length_errors +
+ ring->rx_crc_errors +
+ ring->rx_frame_errors +
+ ring->rx_fifo_errors;
+ stats->rx_dropped += ring->rx_dropped;
+ }
+ }
+ memcpy(storage, stats, sizeof(struct rtnl_link_stats64));
return storage;
}
for (i = 0; i < max_irqs; i++) {
ret = platform_get_irq(pdev, i);
if (ret <= 0) {
+ if (pdata->phy_mode == PHY_INTERFACE_MODE_XGMII) {
+ max_irqs = i;
+ pdata->rxq_cnt = max_irqs / 2;
+ pdata->txq_cnt = max_irqs / 2;
+ pdata->cq_cnt = max_irqs / 2;
+ break;
+ }
dev_err(dev, "Unable to get ENET IRQ\n");
ret = ret ? : -ENXIO;
return ret;
pdata->port_ops = &xgene_xgport_ops;
pdata->cle_ops = &xgene_cle3in_ops;
pdata->rm = RM0;
- pdata->rxq_cnt = XGENE_NUM_RX_RING;
- pdata->txq_cnt = XGENE_NUM_TX_RING;
- pdata->cq_cnt = XGENE_NUM_TXC_RING;
+ if (!pdata->rxq_cnt) {
+ pdata->rxq_cnt = XGENE_NUM_RX_RING;
+ pdata->txq_cnt = XGENE_NUM_TX_RING;
+ pdata->cq_cnt = XGENE_NUM_TXC_RING;
+ }
break;
}
if (pdata->enet_id == XGENE_ENET1) {
switch (pdata->port_id) {
case 0:
- pdata->cpu_bufnum = START_CPU_BUFNUM_0;
- pdata->eth_bufnum = START_ETH_BUFNUM_0;
- pdata->bp_bufnum = START_BP_BUFNUM_0;
- pdata->ring_num = START_RING_NUM_0;
+ if (pdata->phy_mode == PHY_INTERFACE_MODE_XGMII) {
+ pdata->cpu_bufnum = X2_START_CPU_BUFNUM_0;
+ pdata->eth_bufnum = X2_START_ETH_BUFNUM_0;
+ pdata->bp_bufnum = X2_START_BP_BUFNUM_0;
+ pdata->ring_num = START_RING_NUM_0;
+ } else {
+ pdata->cpu_bufnum = START_CPU_BUFNUM_0;
+ pdata->eth_bufnum = START_ETH_BUFNUM_0;
+ pdata->bp_bufnum = START_BP_BUFNUM_0;
+ pdata->ring_num = START_RING_NUM_0;
+ }
break;
case 1:
if (pdata->phy_mode == PHY_INTERFACE_MODE_XGMII) {
ret = xgene_enet_init_hw(pdata);
if (ret)
- goto err;
+ goto err_netdev;
mac_ops = pdata->mac_ops;
if (pdata->phy_mode == PHY_INTERFACE_MODE_RGMII) {
ret = xgene_enet_mdio_config(pdata);
if (ret)
- goto err;
+ goto err_netdev;
} else {
INIT_DELAYED_WORK(&pdata->link_work, mac_ops->link_state);
}
xgene_enet_napi_add(pdata);
return 0;
-err:
+err_netdev:
unregister_netdev(ndev);
+err:
free_netdev(ndev);
return ret;
}
#define XGENE_ENET_MSS 1448
#define XGENE_MIN_ENET_FRAME_SIZE 60
-#define XGENE_MAX_ENET_IRQ 8
-#define XGENE_NUM_RX_RING 4
-#define XGENE_NUM_TX_RING 4
-#define XGENE_NUM_TXC_RING 4
+#define XGENE_MAX_ENET_IRQ 16
+#define XGENE_NUM_RX_RING 8
+#define XGENE_NUM_TX_RING 8
+#define XGENE_NUM_TXC_RING 8
#define START_CPU_BUFNUM_0 0
#define START_ETH_BUFNUM_0 2
struct xgene_enet_raw_desc16 *raw_desc16;
};
__le64 *exp_bufs;
+ u64 tx_packets;
+ u64 tx_bytes;
+ u64 rx_packets;
+ u64 rx_bytes;
+ u64 rx_dropped;
+ u64 rx_errors;
+ u64 rx_length_errors;
+ u64 rx_crc_errors;
+ u64 rx_frame_errors;
+ u64 rx_fifo_errors;
};
struct xgene_mac_ops {
#define LINK_STATUS BIT(2)
#define LINK_UP BIT(15)
#define MPA_IDLE_WITH_QMI_EMPTY BIT(12)
-#define SG_RX_DV_GATE_REG_0_ADDR 0x0dfc
+#define SG_RX_DV_GATE_REG_0_ADDR 0x05fc
extern const struct xgene_mac_ops xgene_sgmac_ops;
extern const struct xgene_port_ops xgene_sgport_ops;
return skb;
}
+static int bnxt_discard_rx(struct bnxt *bp, struct bnxt_napi *bnapi,
+ u32 *raw_cons, void *cmp)
+{
+ struct bnxt_cp_ring_info *cpr = &bnapi->cp_ring;
+ struct rx_cmp *rxcmp = cmp;
+ u32 tmp_raw_cons = *raw_cons;
+ u8 cmp_type, agg_bufs = 0;
+
+ cmp_type = RX_CMP_TYPE(rxcmp);
+
+ if (cmp_type == CMP_TYPE_RX_L2_CMP) {
+ agg_bufs = (le32_to_cpu(rxcmp->rx_cmp_misc_v1) &
+ RX_CMP_AGG_BUFS) >>
+ RX_CMP_AGG_BUFS_SHIFT;
+ } else if (cmp_type == CMP_TYPE_RX_L2_TPA_END_CMP) {
+ struct rx_tpa_end_cmp *tpa_end = cmp;
+
+ agg_bufs = (le32_to_cpu(tpa_end->rx_tpa_end_cmp_misc_v1) &
+ RX_TPA_END_CMP_AGG_BUFS) >>
+ RX_TPA_END_CMP_AGG_BUFS_SHIFT;
+ }
+
+ if (agg_bufs) {
+ if (!bnxt_agg_bufs_valid(bp, cpr, agg_bufs, &tmp_raw_cons))
+ return -EBUSY;
+ }
+ *raw_cons = tmp_raw_cons;
+ return 0;
+}
+
+static void bnxt_sched_reset(struct bnxt *bp, struct bnxt_rx_ring_info *rxr)
+{
+ if (!rxr->bnapi->in_reset) {
+ rxr->bnapi->in_reset = true;
+ set_bit(BNXT_RESET_TASK_SP_EVENT, &bp->sp_event);
+ schedule_work(&bp->sp_task);
+ }
+ rxr->rx_next_cons = 0xffff;
+}
+
static void bnxt_tpa_start(struct bnxt *bp, struct bnxt_rx_ring_info *rxr,
struct rx_tpa_start_cmp *tpa_start,
struct rx_tpa_start_cmp_ext *tpa_start1)
prod_rx_buf = &rxr->rx_buf_ring[prod];
tpa_info = &rxr->rx_tpa[agg_id];
+ if (unlikely(cons != rxr->rx_next_cons)) {
+ bnxt_sched_reset(bp, rxr);
+ return;
+ }
+
prod_rx_buf->data = tpa_info->data;
mapping = tpa_info->mapping;
rxr->rx_prod = NEXT_RX(prod);
cons = NEXT_RX(cons);
+ rxr->rx_next_cons = NEXT_RX(cons);
cons_rx_buf = &rxr->rx_buf_ring[cons];
bnxt_reuse_rx_data(rxr, cons, cons_rx_buf->data);
dma_addr_t mapping;
struct sk_buff *skb;
+ if (unlikely(bnapi->in_reset)) {
+ int rc = bnxt_discard_rx(bp, bnapi, raw_cons, tpa_end);
+
+ if (rc < 0)
+ return ERR_PTR(-EBUSY);
+ return NULL;
+ }
+
tpa_info = &rxr->rx_tpa[agg_id];
data = tpa_info->data;
prefetch(data);
cons = rxcmp->rx_cmp_opaque;
rx_buf = &rxr->rx_buf_ring[cons];
data = rx_buf->data;
+ if (unlikely(cons != rxr->rx_next_cons)) {
+ int rc1 = bnxt_discard_rx(bp, bnapi, raw_cons, rxcmp);
+
+ bnxt_sched_reset(bp, rxr);
+ return rc1;
+ }
prefetch(data);
agg_bufs = (le32_to_cpu(rxcmp->rx_cmp_misc_v1) & RX_CMP_AGG_BUFS) >>
next_rx:
rxr->rx_prod = NEXT_RX(prod);
+ rxr->rx_next_cons = NEXT_RX(cons);
next_rx_no_prod:
*raw_cons = tmp_raw_cons;
if (!TX_CMP_VALID(txcmp, raw_cons))
break;
+ /* The valid test of the entry must be done first before
+ * reading any further.
+ */
+ rmb();
if (TX_CMP_TYPE(txcmp) == CMP_TYPE_TX_L2_CMP) {
tx_pkts++;
/* return full budget so NAPI will complete. */
rxr->rx_prod = 0;
rxr->rx_agg_prod = 0;
rxr->rx_sw_agg_prod = 0;
+ rxr->rx_next_cons = 0;
}
}
}
}
static int bnxt_cfg_rx_mode(struct bnxt *);
+static bool bnxt_mc_list_updated(struct bnxt *, u32 *);
static int bnxt_init_chip(struct bnxt *bp, bool irq_re_init)
{
+ struct bnxt_vnic_info *vnic = &bp->vnic_info[0];
int rc = 0;
if (irq_re_init) {
netdev_err(bp->dev, "HWRM vnic filter failure rc: %x\n", rc);
goto err_out;
}
- bp->vnic_info[0].uc_filter_count = 1;
+ vnic->uc_filter_count = 1;
- bp->vnic_info[0].rx_mask = CFA_L2_SET_RX_MASK_REQ_MASK_BCAST;
+ vnic->rx_mask = CFA_L2_SET_RX_MASK_REQ_MASK_BCAST;
if ((bp->dev->flags & IFF_PROMISC) && BNXT_PF(bp))
- bp->vnic_info[0].rx_mask |=
- CFA_L2_SET_RX_MASK_REQ_MASK_PROMISCUOUS;
+ vnic->rx_mask |= CFA_L2_SET_RX_MASK_REQ_MASK_PROMISCUOUS;
+
+ if (bp->dev->flags & IFF_ALLMULTI) {
+ vnic->rx_mask |= CFA_L2_SET_RX_MASK_REQ_MASK_ALL_MCAST;
+ vnic->mc_list_count = 0;
+ } else {
+ u32 mask = 0;
+
+ bnxt_mc_list_updated(bp, &mask);
+ vnic->rx_mask |= mask;
+ }
rc = bnxt_cfg_rx_mode(bp);
if (rc)
int i;
for (i = 0; i < bp->cp_nr_rings; i++) {
+ bp->bnapi[i]->in_reset = false;
bnxt_enable_poll(bp->bnapi[i]);
napi_enable(&bp->bnapi[i]->napi);
}
u16 rx_prod;
u16 rx_agg_prod;
u16 rx_sw_agg_prod;
+ u16 rx_next_cons;
void __iomem *rx_doorbell;
void __iomem *rx_agg_doorbell;
#ifdef CONFIG_NET_RX_BUSY_POLL
atomic_t poll_state;
#endif
+ bool in_reset;
};
#ifdef CONFIG_NET_RX_BUSY_POLL
nicvf_config_vlan_stripping(nic, nic->netdev->features);
/* Enable Receive queue */
+ memset(&rq_cfg, 0, sizeof(struct rq_cfg));
rq_cfg.ena = 1;
rq_cfg.tcp_ena = 0;
nicvf_queue_reg_write(nic, NIC_QSET_RQ_0_7_CFG, qidx, *(u64 *)&rq_cfg);
qidx, (u64)(cq->dmem.phys_base));
/* Enable Completion queue */
+ memset(&cq_cfg, 0, sizeof(struct cq_cfg));
cq_cfg.ena = 1;
cq_cfg.reset = 0;
cq_cfg.caching = 0;
qidx, (u64)(sq->dmem.phys_base));
/* Enable send queue & set queue size */
+ memset(&sq_cfg, 0, sizeof(struct sq_cfg));
sq_cfg.ena = 1;
sq_cfg.reset = 0;
sq_cfg.ldwb = 0;
/* Enable RBDR & set queue size */
/* Buffer size should be in multiples of 128 bytes */
+ memset(&rbdr_cfg, 0, sizeof(struct rbdr_cfg));
rbdr_cfg.ena = 1;
rbdr_cfg.reset = 0;
rbdr_cfg.ldwb = 0;
u32 tx_ctrl_nt = (tx_ctrl_value & TX_CTL_NT_MASK) >> TX_CTL_NT_SHIFT;
/* Check if we got TX */
- if (!priv->tx_packet_sent || tx_ctrl_ct)
+ if (!priv->tx_skb || tx_ctrl_ct)
return;
/* Ack Tx ctrl register */
}
dev_kfree_skb(priv->tx_skb);
- priv->tx_packet_sent = false;
+ priv->tx_skb = NULL;
if (netif_queue_stopped(ndev))
netif_wake_queue(ndev);
work_done = nps_enet_rx_handler(ndev);
if (work_done < budget) {
u32 buf_int_enable_value = 0;
+ u32 tx_ctrl_value = nps_enet_reg_get(priv, NPS_ENET_REG_TX_CTL);
+ u32 tx_ctrl_ct =
+ (tx_ctrl_value & TX_CTL_CT_MASK) >> TX_CTL_CT_SHIFT;
napi_complete(napi);
nps_enet_reg_set(priv, NPS_ENET_REG_BUF_INT_ENABLE,
buf_int_enable_value);
+
+ /* in case we will get a tx interrupt while interrupts
+ * are masked, we will lose it since the tx is edge interrupt.
+ * specifically, while executing the code section above,
+ * between nps_enet_tx_handler and the interrupts enable, all
+ * tx requests will be stuck until we will get an rx interrupt.
+ * the two code lines below will solve this situation by
+ * re-adding ourselves to the poll list.
+ */
+
+ if (priv->tx_skb && !tx_ctrl_ct)
+ napi_reschedule(napi);
}
return work_done;
u32 tx_ctrl_ct = (tx_ctrl_value & TX_CTL_CT_MASK) >> TX_CTL_CT_SHIFT;
u32 rx_ctrl_cr = (rx_ctrl_value & RX_CTL_CR_MASK) >> RX_CTL_CR_SHIFT;
- if ((!tx_ctrl_ct && priv->tx_packet_sent) || rx_ctrl_cr)
+ if ((!tx_ctrl_ct && priv->tx_skb) || rx_ctrl_cr)
if (likely(napi_schedule_prep(&priv->napi))) {
nps_enet_reg_set(priv, NPS_ENET_REG_BUF_INT_ENABLE, 0);
__napi_schedule(&priv->napi);
/* Write the length of the Frame */
tx_ctrl_value |= length << TX_CTL_NT_SHIFT;
- /* Indicate SW is done */
- priv->tx_packet_sent = true;
tx_ctrl_value |= NPS_ENET_ENABLE << TX_CTL_CT_SHIFT;
/* Send Frame */
nps_enet_reg_set(priv, NPS_ENET_REG_TX_CTL, tx_ctrl_value);
s32 err;
/* Reset private variables */
- priv->tx_packet_sent = false;
+ priv->tx_skb = NULL;
priv->ge_mac_cfg_2_value = 0;
priv->ge_mac_cfg_3_value = 0;
priv->tx_skb = skb;
+ /* make sure tx_skb is actually written to the memory
+ * before the HW is informed and the IRQ is fired.
+ */
+ wmb();
+
nps_enet_send_frame(ndev, skb);
return NETDEV_TX_OK;
* struct nps_enet_priv - Storage of ENET's private information.
* @regs_base: Base address of ENET memory-mapped control registers.
* @irq: For RX/TX IRQ number.
- * @tx_packet_sent: SW indication if frame is being sent.
* @tx_skb: socket buffer of sent frame.
* @napi: Structure for NAPI.
*/
struct nps_enet_priv {
void __iomem *regs_base;
s32 irq;
- bool tx_packet_sent;
struct sk_buff *tx_skb;
struct napi_struct napi;
u32 ge_mac_cfg_2_value;
struct fec_enet_private *fep = netdev_priv(ndev);
for_each_set_bit(queue_id, &fep->work_rx, FEC_ENET_MAX_RX_QS) {
- clear_bit(queue_id, &fep->work_rx);
- pkt_received += fec_enet_rx_queue(ndev,
+ int ret;
+
+ ret = fec_enet_rx_queue(ndev,
budget - pkt_received, queue_id);
+
+ if (ret < budget - pkt_received)
+ clear_bit(queue_id, &fep->work_rx);
+
+ pkt_received += ret;
}
return pkt_received;
}
config MVNETA_BM
tristate
- default y if MVNETA=y && MVNETA_BM_ENABLE
+ default y if MVNETA=y && MVNETA_BM_ENABLE!=n
default MVNETA_BM_ENABLE
select HWBM
help
if (ipv6h->nexthdr == IPPROTO_FRAGMENT || ipv6h->nexthdr == IPPROTO_HOPOPTS)
return -1;
- hw_checksum = csum_add(hw_checksum, (__force __wsum)(ipv6h->nexthdr << 8));
+ hw_checksum = csum_add(hw_checksum, (__force __wsum)htons(ipv6h->nexthdr));
csum_pseudo_hdr = csum_partial(&ipv6h->saddr,
sizeof(ipv6h->saddr) + sizeof(ipv6h->daddr), 0);
bool "Mellanox Technologies ConnectX-4 Ethernet support"
depends on NETDEVICES && ETHERNET && PCI && MLX5_CORE
select PTP_1588_CLOCK
- select VXLAN if MLX5_CORE=y
default n
---help---
Ethernet support in Mellanox Technologies ConnectX-4 NIC.
This flag is depended on the kernel's DCB support.
If unsure, set to Y
+
+config MLX5_CORE_EN_VXLAN
+ bool "VXLAN offloads Support"
+ default y
+ depends on MLX5_CORE_EN && VXLAN && !(MLX5_CORE=y && VXLAN=m)
+ ---help---
+ Say Y here if you want to use VXLAN offloads in the driver.
mlx5_core-$(CONFIG_MLX5_CORE_EN) += wq.o eswitch.o \
en_main.o en_fs.o en_ethtool.o en_tx.o en_rx.o \
- en_txrx.o en_clock.o vxlan.o en_tc.o
+ en_txrx.o en_clock.o en_tc.o
+mlx5_core-$(CONFIG_MLX5_CORE_EN_VXLAN) += vxlan.o
mlx5_core-$(CONFIG_MLX5_CORE_EN_DCB) += en_dcbnl.o
struct mlx5e_flow_tables fts;
struct mlx5e_eth_addr_db eth_addr;
struct mlx5e_vlan_db vlan;
+#ifdef CONFIG_MLX5_CORE_EN_VXLAN
struct mlx5e_vxlan_db vxlan;
+#endif
struct mlx5e_params params;
struct workqueue_struct *wq;
vf_stats);
}
+#if IS_ENABLED(CONFIG_MLX5_CORE_EN_VXLAN)
static void mlx5e_add_vxlan_port(struct net_device *netdev,
sa_family_t sa_family, __be16 port)
{
return features;
}
+#endif
static const struct net_device_ops mlx5e_netdev_ops_basic = {
.ndo_open = mlx5e_open,
.ndo_set_features = mlx5e_set_features,
.ndo_change_mtu = mlx5e_change_mtu,
.ndo_do_ioctl = mlx5e_ioctl,
+#ifdef CONFIG_MLX5_CORE_EN_VXLAN
.ndo_add_vxlan_port = mlx5e_add_vxlan_port,
.ndo_del_vxlan_port = mlx5e_del_vxlan_port,
.ndo_features_check = mlx5e_features_check,
+#endif
.ndo_set_vf_mac = mlx5e_set_vf_mac,
.ndo_set_vf_vlan = mlx5e_set_vf_vlan,
.ndo_get_vf_config = mlx5e_get_vf_config,
static inline bool mlx5e_vxlan_allowed(struct mlx5_core_dev *mdev)
{
- return (MLX5_CAP_ETH(mdev, tunnel_stateless_vxlan) &&
+ return IS_ENABLED(CONFIG_MLX5_CORE_EN_VXLAN) &&
+ (MLX5_CAP_ETH(mdev, tunnel_stateless_vxlan) &&
mlx5_core_is_pf(mdev));
}
+#ifdef CONFIG_MLX5_CORE_EN_VXLAN
void mlx5e_vxlan_init(struct mlx5e_priv *priv);
+void mlx5e_vxlan_cleanup(struct mlx5e_priv *priv);
+#else
+static inline void mlx5e_vxlan_init(struct mlx5e_priv *priv) {}
+static inline void mlx5e_vxlan_cleanup(struct mlx5e_priv *priv) {}
+#endif
+
void mlx5e_vxlan_queue_work(struct mlx5e_priv *priv, sa_family_t sa_family,
u16 port, int add);
struct mlx5e_vxlan *mlx5e_vxlan_lookup_port(struct mlx5e_priv *priv, u16 port);
-void mlx5e_vxlan_cleanup(struct mlx5e_priv *priv);
#endif /* __MLX5_VXLAN_H__ */
lag->ref_count++;
return 0;
+err_col_port_enable:
+ mlxsw_sp_lag_col_port_remove(mlxsw_sp_port, lag_id);
err_col_port_add:
if (!lag->ref_count)
mlxsw_sp_lag_destroy(mlxsw_sp, lag_id);
-err_col_port_enable:
- mlxsw_sp_lag_col_port_remove(mlxsw_sp_port, lag_id);
return err;
}
mlxsw_reg_sftr_pack(sftr_pl, MLXSW_SP_FLOOD_TABLE_BM, idx_begin,
table_type, range, local_port, set);
err = mlxsw_reg_write(mlxsw_sp->core, MLXSW_REG(sftr), sftr_pl);
+ if (err)
+ goto err_flood_bm_set;
+ else
+ goto buffer_out;
+err_flood_bm_set:
+ mlxsw_reg_sftr_pack(sftr_pl, MLXSW_SP_FLOOD_TABLE_UC, idx_begin,
+ table_type, range, local_port, !set);
+ mlxsw_reg_write(mlxsw_sp->core, MLXSW_REG(sftr), sftr_pl);
buffer_out:
kfree(sftr_pl);
return err;
{
int i, v, addr;
__le32 *ptr32;
+ int ret;
addr = base;
ptr32 = buf;
for (i = 0; i < size / sizeof(u32); i++) {
- if (netxen_rom_fast_read(adapter, addr, &v) == -1)
- return -1;
+ ret = netxen_rom_fast_read(adapter, addr, &v);
+ if (ret)
+ return ret;
+
*ptr32 = cpu_to_le32(v);
ptr32++;
addr += sizeof(u32);
}
if ((char *)buf + size > (char *)ptr32) {
__le32 local;
- if (netxen_rom_fast_read(adapter, addr, &v) == -1)
- return -1;
+ ret = netxen_rom_fast_read(adapter, addr, &v);
+ if (ret)
+ return ret;
local = cpu_to_le32(v);
memcpy(ptr32, &local, (char *)buf + size - (char *)ptr32);
}
if (adapter->phy_read &&
adapter->phy_read(adapter,
NETXEN_NIU_GB_MII_MGMT_ADDR_AUTONEG,
- &autoneg) != 0)
+ &autoneg) == 0)
adapter->link_autoneg = autoneg;
} else
goto link_down;
ptr32 = (__le32 *)&serial_num;
offset = NX_FW_SERIAL_NUM_OFFSET;
for (i = 0; i < 8; i++) {
- if (netxen_rom_fast_read(adapter, offset, &val) == -1) {
+ err = netxen_rom_fast_read(adapter, offset, &val);
+ if (err) {
dev_err(&pdev->dev, "error reading board info\n");
adapter->driver_mismatch = 1;
return;
u8 xmit_type;
u16 idx;
u16 hlen;
- bool data_split;
+ bool data_split = false;
/* Get tx-queue context and netdev index */
txq_index = skb_get_queue_mapping(skb);
edev->q_num_rx_buffers = NUM_RX_BDS_DEF;
edev->q_num_tx_buffers = NUM_TX_BDS_DEF;
- DP_INFO(edev, "Allocated netdev with 64 tx queues and 64 rx queues\n");
-
SET_NETDEV_DEV(ndev, &pdev->dev);
memset(&edev->stats, 0, sizeof(edev->stats));
{
struct qed_pf_params pf_params;
- /* 16 rx + 16 tx */
+ /* 64 rx + 64 tx */
memset(&pf_params, 0, sizeof(struct qed_pf_params));
- pf_params.eth_pf_params.num_cons = 32;
+ pf_params.eth_pf_params.num_cons = 128;
qed_ops->common->update_pf_params(cdev, &pf_params);
}
struct qlcnic_fw_dump *fw_dump = &ahw->fw_dump;
struct pci_dev *pdev = adapter->pdev;
bool extended = false;
+ int ret;
prev_version = adapter->fw_version;
current_version = qlcnic_83xx_get_fw_version(adapter);
if (qlcnic_83xx_md_check_extended_dump_capability(adapter))
extended = !qlcnic_83xx_extend_md_capab(adapter);
- if (!qlcnic_fw_cmd_get_minidump_temp(adapter))
- dev_info(&pdev->dev, "Supports FW dump capability\n");
+ ret = qlcnic_fw_cmd_get_minidump_temp(adapter);
+ if (ret)
+ return;
+
+ dev_info(&pdev->dev, "Supports FW dump capability\n");
/* Once we have minidump template with extended iSCSI dump
* capability, update the minidump capture mask to 0x1f as
priv->phydev = NULL;
}
+ if (priv->chip_id == RCAR_GEN3)
+ free_irq(priv->emac_irq, ndev);
free_irq(ndev->irq, ndev);
napi_disable(&priv->napi[RAVB_NC]);
int gh_len;
int err = -ENOSYS;
- udp_tunnel_gro_complete(skb, nhoff);
-
gh = (struct genevehdr *)(skb->data + nhoff);
gh_len = geneve_hlen(gh);
type = gh->proto_type;
err = ptype->callbacks.gro_complete(skb, nhoff + gh_len);
rcu_read_unlock();
+
+ skb_set_inner_mac_header(skb, nhoff + gh_len);
+
return err;
}
* @tfm: crypto struct, key storage
*/
struct macsec_key {
- u64 id;
+ u8 id[MACSEC_KEYID_LEN];
struct crypto_aead *tfm;
};
[MACSEC_SA_ATTR_AN] = { .type = NLA_U8 },
[MACSEC_SA_ATTR_ACTIVE] = { .type = NLA_U8 },
[MACSEC_SA_ATTR_PN] = { .type = NLA_U32 },
- [MACSEC_SA_ATTR_KEYID] = { .type = NLA_U64 },
+ [MACSEC_SA_ATTR_KEYID] = { .type = NLA_BINARY,
+ .len = MACSEC_KEYID_LEN, },
[MACSEC_SA_ATTR_KEY] = { .type = NLA_BINARY,
.len = MACSEC_MAX_KEY_LEN, },
};
return false;
}
+ if (nla_len(attrs[MACSEC_SA_ATTR_KEYID]) != MACSEC_KEYID_LEN)
+ return false;
+
return true;
}
if (tb_sa[MACSEC_SA_ATTR_ACTIVE])
rx_sa->active = !!nla_get_u8(tb_sa[MACSEC_SA_ATTR_ACTIVE]);
- rx_sa->key.id = nla_get_u64(tb_sa[MACSEC_SA_ATTR_KEYID]);
+ nla_memcpy(rx_sa->key.id, tb_sa[MACSEC_SA_ATTR_KEY], MACSEC_KEYID_LEN);
rx_sa->sc = rx_sc;
rcu_assign_pointer(rx_sc->sa[assoc_num], rx_sa);
return false;
}
+ if (nla_len(attrs[MACSEC_SA_ATTR_KEYID]) != MACSEC_KEYID_LEN)
+ return false;
+
return true;
}
return -ENOMEM;
}
- tx_sa->key.id = nla_get_u64(tb_sa[MACSEC_SA_ATTR_KEYID]);
+ nla_memcpy(tx_sa->key.id, tb_sa[MACSEC_SA_ATTR_KEY], MACSEC_KEYID_LEN);
spin_lock_bh(&tx_sa->lock);
tx_sa->next_pn = nla_get_u32(tb_sa[MACSEC_SA_ATTR_PN]);
if (nla_put_u8(skb, MACSEC_SA_ATTR_AN, i) ||
nla_put_u32(skb, MACSEC_SA_ATTR_PN, tx_sa->next_pn) ||
- nla_put_u64(skb, MACSEC_SA_ATTR_KEYID, tx_sa->key.id) ||
+ nla_put(skb, MACSEC_SA_ATTR_KEYID, MACSEC_KEYID_LEN, tx_sa->key.id) ||
nla_put_u8(skb, MACSEC_SA_ATTR_ACTIVE, tx_sa->active)) {
nla_nest_cancel(skb, txsa_nest);
nla_nest_cancel(skb, txsa_list);
if (nla_put_u8(skb, MACSEC_SA_ATTR_AN, i) ||
nla_put_u32(skb, MACSEC_SA_ATTR_PN, rx_sa->next_pn) ||
- nla_put_u64(skb, MACSEC_SA_ATTR_KEYID, rx_sa->key.id) ||
+ nla_put(skb, MACSEC_SA_ATTR_KEYID, MACSEC_KEYID_LEN, rx_sa->key.id) ||
nla_put_u8(skb, MACSEC_SA_ATTR_ACTIVE, rx_sa->active)) {
nla_nest_cancel(skb, rxsa_nest);
nla_nest_cancel(skb, rxsc_nest);
goto wake_up;
}
- kfree_skb(skb);
+ consume_skb(skb);
while (segs) {
struct sk_buff *nskb = segs->next;
break;
case PHY_HALTED:
/* make sure interrupts are re-enabled for the PHY */
- err = phy_enable_interrupts(phydev);
- if (err < 0)
- break;
+ if (phydev->irq != PHY_POLL) {
+ err = phy_enable_interrupts(phydev);
+ if (err < 0)
+ break;
+ }
phydev->state = PHY_RESUMING;
do_resume = true;
static int vxlan_gro_complete(struct sk_buff *skb, int nhoff,
struct udp_offload *uoff)
{
- udp_tunnel_gro_complete(skb, nhoff);
-
+ /* Sets 'skb->inner_mac_header' since we are always called with
+ * 'skb->encapsulation' set.
+ */
return eth_gro_complete(skb, nhoff + sizeof(struct vxlanhdr));
}
struct iwl_tx_cmd *tx_cmd,
struct ieee80211_tx_info *info, u8 sta_id)
{
+ struct ieee80211_tx_info *skb_info = IEEE80211_SKB_CB(skb);
struct ieee80211_hdr *hdr = (void *)skb->data;
__le16 fc = hdr->frame_control;
u32 tx_flags = le32_to_cpu(tx_cmd->tx_flags);
tx_cmd->tx_flags = cpu_to_le32(tx_flags);
/* Total # bytes to be transmitted */
tx_cmd->len = cpu_to_le16((u16)skb->len +
- (uintptr_t)info->driver_data[0]);
+ (uintptr_t)skb_info->driver_data[0]);
tx_cmd->next_frame_len = 0;
tx_cmd->life_time = cpu_to_le32(TX_CMD_LIFE_TIME_INFINITE);
tx_cmd->sta_id = sta_id;
*/
static struct iwl_device_cmd *
iwl_mvm_set_tx_params(struct iwl_mvm *mvm, struct sk_buff *skb,
- int hdrlen, struct ieee80211_sta *sta, u8 sta_id)
+ struct ieee80211_tx_info *info, int hdrlen,
+ struct ieee80211_sta *sta, u8 sta_id)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
- struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+ struct ieee80211_tx_info *skb_info = IEEE80211_SKB_CB(skb);
struct iwl_device_cmd *dev_cmd;
struct iwl_tx_cmd *tx_cmd;
iwl_mvm_set_tx_cmd_rate(mvm, tx_cmd, info, sta, hdr->frame_control);
- memset(&info->status, 0, sizeof(info->status));
- memset(info->driver_data, 0, sizeof(info->driver_data));
+ memset(&skb_info->status, 0, sizeof(skb_info->status));
+ memset(skb_info->driver_data, 0, sizeof(skb_info->driver_data));
- info->driver_data[1] = dev_cmd;
+ skb_info->driver_data[1] = dev_cmd;
return dev_cmd;
}
int iwl_mvm_tx_skb_non_sta(struct iwl_mvm *mvm, struct sk_buff *skb)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
- struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+ struct ieee80211_tx_info *skb_info = IEEE80211_SKB_CB(skb);
+ struct ieee80211_tx_info info;
struct iwl_device_cmd *dev_cmd;
struct iwl_tx_cmd *tx_cmd;
u8 sta_id;
int hdrlen = ieee80211_hdrlen(hdr->frame_control);
- if (WARN_ON_ONCE(info->flags & IEEE80211_TX_CTL_AMPDU))
+ memcpy(&info, skb->cb, sizeof(info));
+
+ if (WARN_ON_ONCE(info.flags & IEEE80211_TX_CTL_AMPDU))
return -1;
- if (WARN_ON_ONCE(info->flags & IEEE80211_TX_CTL_SEND_AFTER_DTIM &&
- (!info->control.vif ||
- info->hw_queue != info->control.vif->cab_queue)))
+ if (WARN_ON_ONCE(info.flags & IEEE80211_TX_CTL_SEND_AFTER_DTIM &&
+ (!info.control.vif ||
+ info.hw_queue != info.control.vif->cab_queue)))
return -1;
/* This holds the amsdu headers length */
- info->driver_data[0] = (void *)(uintptr_t)0;
+ skb_info->driver_data[0] = (void *)(uintptr_t)0;
/*
* IWL_MVM_OFFCHANNEL_QUEUE is used for ROC packets that can be used
* and hence needs to be sent on the aux queue
*/
if (IEEE80211_SKB_CB(skb)->hw_queue == IWL_MVM_OFFCHANNEL_QUEUE &&
- info->control.vif->type == NL80211_IFTYPE_STATION)
+ info.control.vif->type == NL80211_IFTYPE_STATION)
IEEE80211_SKB_CB(skb)->hw_queue = mvm->aux_queue;
/*
* AUX station.
*/
sta_id = mvm->aux_sta.sta_id;
- if (info->control.vif) {
+ if (info.control.vif) {
struct iwl_mvm_vif *mvmvif =
- iwl_mvm_vif_from_mac80211(info->control.vif);
+ iwl_mvm_vif_from_mac80211(info.control.vif);
- if (info->control.vif->type == NL80211_IFTYPE_P2P_DEVICE ||
- info->control.vif->type == NL80211_IFTYPE_AP)
+ if (info.control.vif->type == NL80211_IFTYPE_P2P_DEVICE ||
+ info.control.vif->type == NL80211_IFTYPE_AP)
sta_id = mvmvif->bcast_sta.sta_id;
- else if (info->control.vif->type == NL80211_IFTYPE_STATION &&
+ else if (info.control.vif->type == NL80211_IFTYPE_STATION &&
is_multicast_ether_addr(hdr->addr1)) {
u8 ap_sta_id = ACCESS_ONCE(mvmvif->ap_sta_id);
}
}
- IWL_DEBUG_TX(mvm, "station Id %d, queue=%d\n", sta_id, info->hw_queue);
+ IWL_DEBUG_TX(mvm, "station Id %d, queue=%d\n", sta_id, info.hw_queue);
- dev_cmd = iwl_mvm_set_tx_params(mvm, skb, hdrlen, NULL, sta_id);
+ dev_cmd = iwl_mvm_set_tx_params(mvm, skb, &info, hdrlen, NULL, sta_id);
if (!dev_cmd)
return -1;
- /* From now on, we cannot access info->control */
tx_cmd = (struct iwl_tx_cmd *)dev_cmd->payload;
/* Copy MAC header from skb into command buffer */
memcpy(tx_cmd->hdr, hdr, hdrlen);
- if (iwl_trans_tx(mvm->trans, skb, dev_cmd, info->hw_queue)) {
+ if (iwl_trans_tx(mvm->trans, skb, dev_cmd, info.hw_queue)) {
iwl_trans_free_tx_cmd(mvm->trans, dev_cmd);
return -1;
}
#ifdef CONFIG_INET
static int iwl_mvm_tx_tso(struct iwl_mvm *mvm, struct sk_buff *skb,
+ struct ieee80211_tx_info *info,
struct ieee80211_sta *sta,
struct sk_buff_head *mpdus_skb)
{
struct iwl_mvm_sta *mvmsta = iwl_mvm_sta_from_mac80211(sta);
- struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
struct ieee80211_hdr *hdr = (void *)skb->data;
unsigned int mss = skb_shinfo(skb)->gso_size;
struct sk_buff *tmp, *next;
/* This skb fits in one single A-MSDU */
if (num_subframes * mss >= tcp_payload_len) {
+ struct ieee80211_tx_info *skb_info = IEEE80211_SKB_CB(skb);
+
/*
* Compute the length of all the data added for the A-MSDU.
* This will be used to compute the length to write in the TX
* already had one set of SNAP / IP / TCP headers.
*/
num_subframes = DIV_ROUND_UP(tcp_payload_len, mss);
- info = IEEE80211_SKB_CB(skb);
amsdu_add = num_subframes * sizeof(struct ethhdr) +
(num_subframes - 1) * (snap_ip_tcp + pad);
/* This holds the amsdu headers length */
- info->driver_data[0] = (void *)(uintptr_t)amsdu_add;
+ skb_info->driver_data[0] = (void *)(uintptr_t)amsdu_add;
__skb_queue_tail(mpdus_skb, skb);
return 0;
ip_hdr(tmp)->id = htons(ip_base_id + i * num_subframes);
if (tcp_payload_len > mss) {
+ struct ieee80211_tx_info *skb_info =
+ IEEE80211_SKB_CB(tmp);
+
num_subframes = DIV_ROUND_UP(tcp_payload_len, mss);
- info = IEEE80211_SKB_CB(tmp);
amsdu_add = num_subframes * sizeof(struct ethhdr) +
(num_subframes - 1) * (snap_ip_tcp + pad);
- info->driver_data[0] = (void *)(uintptr_t)amsdu_add;
+ skb_info->driver_data[0] =
+ (void *)(uintptr_t)amsdu_add;
skb_shinfo(tmp)->gso_size = mss;
} else {
qc = ieee80211_get_qos_ctl((void *)tmp->data);
}
#else /* CONFIG_INET */
static int iwl_mvm_tx_tso(struct iwl_mvm *mvm, struct sk_buff *skb,
+ struct ieee80211_tx_info *info,
struct ieee80211_sta *sta,
struct sk_buff_head *mpdus_skb)
{
* Sets the fields in the Tx cmd that are crypto related
*/
static int iwl_mvm_tx_mpdu(struct iwl_mvm *mvm, struct sk_buff *skb,
+ struct ieee80211_tx_info *info,
struct ieee80211_sta *sta)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
- struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
struct iwl_mvm_sta *mvmsta;
struct iwl_device_cmd *dev_cmd;
struct iwl_tx_cmd *tx_cmd;
if (WARN_ON_ONCE(mvmsta->sta_id == IWL_MVM_STATION_COUNT))
return -1;
- dev_cmd = iwl_mvm_set_tx_params(mvm, skb, hdrlen, sta, mvmsta->sta_id);
+ dev_cmd = iwl_mvm_set_tx_params(mvm, skb, info, hdrlen,
+ sta, mvmsta->sta_id);
if (!dev_cmd)
goto drop;
struct ieee80211_sta *sta)
{
struct iwl_mvm_sta *mvmsta = iwl_mvm_sta_from_mac80211(sta);
- struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+ struct ieee80211_tx_info *skb_info = IEEE80211_SKB_CB(skb);
+ struct ieee80211_tx_info info;
struct sk_buff_head mpdus_skbs;
unsigned int payload_len;
int ret;
if (WARN_ON_ONCE(mvmsta->sta_id == IWL_MVM_STATION_COUNT))
return -1;
+ memcpy(&info, skb->cb, sizeof(info));
+
/* This holds the amsdu headers length */
- info->driver_data[0] = (void *)(uintptr_t)0;
+ skb_info->driver_data[0] = (void *)(uintptr_t)0;
if (!skb_is_gso(skb))
- return iwl_mvm_tx_mpdu(mvm, skb, sta);
+ return iwl_mvm_tx_mpdu(mvm, skb, &info, sta);
payload_len = skb_tail_pointer(skb) - skb_transport_header(skb) -
tcp_hdrlen(skb) + skb->data_len;
if (payload_len <= skb_shinfo(skb)->gso_size)
- return iwl_mvm_tx_mpdu(mvm, skb, sta);
+ return iwl_mvm_tx_mpdu(mvm, skb, &info, sta);
__skb_queue_head_init(&mpdus_skbs);
- ret = iwl_mvm_tx_tso(mvm, skb, sta, &mpdus_skbs);
+ ret = iwl_mvm_tx_tso(mvm, skb, &info, sta, &mpdus_skbs);
if (ret)
return ret;
while (!skb_queue_empty(&mpdus_skbs)) {
skb = __skb_dequeue(&mpdus_skbs);
- ret = iwl_mvm_tx_mpdu(mvm, skb, sta);
+ ret = iwl_mvm_tx_mpdu(mvm, skb, &info, sta);
if (ret) {
__skb_queue_purge(&mpdus_skbs);
return ret;
if (cons == end)
break;
RING_COPY_REQUEST(&queue->tx, cons++, txp);
+ extra_count = 0; /* only the first frag can have extras */
} while (1);
queue->tx.req_cons = cons;
}
/*
* vmemmap_populate_hugepages() allocates the memmap array in
- * HPAGE_SIZE chunks.
+ * PMD_SIZE chunks.
*/
- memmap_size = ALIGN(64 * npfns, HPAGE_SIZE);
+ memmap_size = ALIGN(64 * npfns, PMD_SIZE);
offset = ALIGN(start + SZ_8K + memmap_size, nd_pfn->align)
- start;
} else if (nd_pfn->mode == PFN_MODE_RAM)
if (ret)
goto close_banks;
- while (val_size) {
+ while (val_size >= reg_size) {
if ((offset < OCOTP_DATA_OFFSET) || (offset % 16)) {
/* fill up non-data register */
*buf = 0;
}
buf++;
- val_size--;
+ val_size -= reg_size;
offset += reg_size;
}
dev->match_driver = true;
retval = device_attach(&dev->dev);
- if (retval < 0) {
+ if (retval < 0 && retval != -EPROBE_DEFER) {
dev_warn(&dev->dev, "device attach failed (%d)\n", retval);
pci_proc_detach_device(dev);
pci_remove_sysfs_dev_files(dev);
}
list_for_each_entry(dev, &bus->devices, bus_list) {
- BUG_ON(!dev->is_added);
+ /* Skip if device attach failed */
+ if (!dev->is_added)
+ continue;
child = dev->subordinate;
if (child)
pci_bus_add_devices(child);
break;
case PIN_CONFIG_BIAS_PULL_UP:
conf |= ATMEL_PIO_PUEN_MASK;
+ conf &= (~ATMEL_PIO_PDEN_MASK);
break;
case PIN_CONFIG_BIAS_PULL_DOWN:
conf |= ATMEL_PIO_PDEN_MASK;
+ conf &= (~ATMEL_PIO_PUEN_MASK);
break;
case PIN_CONFIG_DRIVE_OPEN_DRAIN:
if (arg == 0)
static const struct regulator_linear_range axp20x_ldo4_ranges[] = {
REGULATOR_LINEAR_RANGE(1250000, 0x0, 0x0, 0),
REGULATOR_LINEAR_RANGE(1300000, 0x1, 0x8, 100000),
- REGULATOR_LINEAR_RANGE(2500000, 0x9, 0xf, 100000),
+ REGULATOR_LINEAR_RANGE(2500000, 0x9, 0x9, 0),
+ REGULATOR_LINEAR_RANGE(2700000, 0xa, 0xb, 100000),
+ REGULATOR_LINEAR_RANGE(3000000, 0xc, 0xf, 100000),
};
static const struct regulator_desc axp20x_regulators[] = {
AXP22X_ELDO2_V_OUT, 0x1f, AXP22X_PWR_OUT_CTRL2, BIT(1)),
AXP_DESC(AXP22X, ELDO3, "eldo3", "eldoin", 700, 3300, 100,
AXP22X_ELDO3_V_OUT, 0x1f, AXP22X_PWR_OUT_CTRL2, BIT(2)),
- AXP_DESC_IO(AXP22X, LDO_IO0, "ldo_io0", "ips", 1800, 3300, 100,
+ /* Note the datasheet only guarantees reliable operation up to
+ * 3.3V, this needs to be enforced via dts provided constraints */
+ AXP_DESC_IO(AXP22X, LDO_IO0, "ldo_io0", "ips", 700, 3800, 100,
AXP22X_LDO_IO0_V_OUT, 0x1f, AXP20X_GPIO0_CTRL, 0x07,
AXP22X_IO_ENABLED, AXP22X_IO_DISABLED),
- AXP_DESC_IO(AXP22X, LDO_IO1, "ldo_io1", "ips", 1800, 3300, 100,
+ /* Note the datasheet only guarantees reliable operation up to
+ * 3.3V, this needs to be enforced via dts provided constraints */
+ AXP_DESC_IO(AXP22X, LDO_IO1, "ldo_io1", "ips", 700, 3800, 100,
AXP22X_LDO_IO1_V_OUT, 0x1f, AXP20X_GPIO1_CTRL, 0x07,
AXP22X_IO_ENABLED, AXP22X_IO_DISABLED),
AXP_DESC_FIXED(AXP22X, RTC_LDO, "rtc_ldo", "ips", 3000),
MODULE_AUTHOR("Krystian Garbaciak <krystian.garbaciak@diasemi.com>");
MODULE_DESCRIPTION("DA9063 regulators driver");
MODULE_LICENSE("GPL");
-MODULE_ALIAS("paltform:" DA9063_DRVNAME_REGULATORS);
+MODULE_ALIAS("platform:" DA9063_DRVNAME_REGULATORS);
of_property_read_u32(np, "startup-delay-us", &config->startup_delay);
config->enable_gpio = of_get_named_gpio(np, "enable-gpio", 0);
+ if (config->enable_gpio == -EPROBE_DEFER)
+ return ERR_PTR(-EPROBE_DEFER);
/* Fetch GPIOs. - optional property*/
ret = of_gpio_count(np);
.enable_mask = S2MPS11_ENABLE_MASK \
}
-#define regulator_desc_s2mps11_buck6_10(num, min, step) { \
+#define regulator_desc_s2mps11_buck67810(num, min, step) { \
.name = "BUCK"#num, \
.id = S2MPS11_BUCK##num, \
.ops = &s2mps11_buck_ops, \
.enable_mask = S2MPS11_ENABLE_MASK \
}
+#define regulator_desc_s2mps11_buck9 { \
+ .name = "BUCK9", \
+ .id = S2MPS11_BUCK9, \
+ .ops = &s2mps11_buck_ops, \
+ .type = REGULATOR_VOLTAGE, \
+ .owner = THIS_MODULE, \
+ .min_uV = MIN_3000_MV, \
+ .uV_step = STEP_25_MV, \
+ .n_voltages = S2MPS11_BUCK9_N_VOLTAGES, \
+ .ramp_delay = S2MPS11_RAMP_DELAY, \
+ .vsel_reg = S2MPS11_REG_B9CTRL2, \
+ .vsel_mask = S2MPS11_BUCK9_VSEL_MASK, \
+ .enable_reg = S2MPS11_REG_B9CTRL1, \
+ .enable_mask = S2MPS11_ENABLE_MASK \
+}
+
static const struct regulator_desc s2mps11_regulators[] = {
regulator_desc_s2mps11_ldo(1, STEP_25_MV),
regulator_desc_s2mps11_ldo(2, STEP_50_MV),
regulator_desc_s2mps11_buck1_4(3),
regulator_desc_s2mps11_buck1_4(4),
regulator_desc_s2mps11_buck5,
- regulator_desc_s2mps11_buck6_10(6, MIN_600_MV, STEP_6_25_MV),
- regulator_desc_s2mps11_buck6_10(7, MIN_600_MV, STEP_6_25_MV),
- regulator_desc_s2mps11_buck6_10(8, MIN_600_MV, STEP_6_25_MV),
- regulator_desc_s2mps11_buck6_10(9, MIN_3000_MV, STEP_25_MV),
- regulator_desc_s2mps11_buck6_10(10, MIN_750_MV, STEP_12_5_MV),
+ regulator_desc_s2mps11_buck67810(6, MIN_600_MV, STEP_6_25_MV),
+ regulator_desc_s2mps11_buck67810(7, MIN_600_MV, STEP_6_25_MV),
+ regulator_desc_s2mps11_buck67810(8, MIN_600_MV, STEP_6_25_MV),
+ regulator_desc_s2mps11_buck9,
+ regulator_desc_s2mps11_buck67810(10, MIN_750_MV, STEP_12_5_MV),
};
static struct regulator_ops s2mps14_reg_ops;
return SCSI_DH_DEV_TEMP_BUSY;
retry:
+ err = 0;
retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
if (retval) {
.eh_bus_reset_handler = qla1280_eh_bus_reset,
.eh_host_reset_handler = qla1280_eh_adapter_reset,
.bios_param = qla1280_biosparam,
- .can_queue = 0xfffff,
+ .can_queue = MAX_OUTSTANDING_COMMANDS,
.this_id = -1,
.sg_tablesize = SG_ALL,
.use_clustering = ENABLE_CLUSTERING,
dspi->cur_chip = spi_get_ctldata(spi);
dspi->cs = spi->chip_select;
dspi->cs_change = 0;
- if (dspi->cur_transfer->transfer_list.next
- == &dspi->cur_msg->transfers)
+ if (list_is_last(&dspi->cur_transfer->transfer_list,
+ &dspi->cur_msg->transfers) || transfer->cs_change)
dspi->cs_change = 1;
dspi->void_write_data = dspi->cur_chip->void_write_data;
if (mcspi_dma->dma_tx) {
struct dma_async_tx_descriptor *tx;
+ struct scatterlist sg;
dmaengine_slave_config(mcspi_dma->dma_tx, &cfg);
- tx = dmaengine_prep_slave_sg(mcspi_dma->dma_tx, xfer->tx_sg.sgl,
- xfer->tx_sg.nents, DMA_MEM_TO_DEV,
- DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ sg_init_table(&sg, 1);
+ sg_dma_address(&sg) = xfer->tx_dma;
+ sg_dma_len(&sg) = xfer->len;
+
+ tx = dmaengine_prep_slave_sg(mcspi_dma->dma_tx, &sg, 1,
+ DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (tx) {
tx->callback = omap2_mcspi_tx_callback;
tx->callback_param = spi;
if (mcspi_dma->dma_rx) {
struct dma_async_tx_descriptor *tx;
+ struct scatterlist sg;
dmaengine_slave_config(mcspi_dma->dma_rx, &cfg);
if ((l & OMAP2_MCSPI_CHCONF_TURBO) && mcspi->fifo_depth == 0)
dma_count -= es;
- tx = dmaengine_prep_slave_sg(mcspi_dma->dma_rx, xfer->rx_sg.sgl,
- xfer->rx_sg.nents, DMA_DEV_TO_MEM,
- DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ sg_init_table(&sg, 1);
+ sg_dma_address(&sg) = xfer->rx_dma;
+ sg_dma_len(&sg) = dma_count;
+
+ tx = dmaengine_prep_slave_sg(mcspi_dma->dma_rx, &sg, 1,
+ DMA_DEV_TO_MEM, DMA_PREP_INTERRUPT |
+ DMA_CTRL_ACK);
if (tx) {
tx->callback = omap2_mcspi_rx_callback;
tx->callback_param = spi;
omap2_mcspi_set_dma_req(spi, 1, 1);
wait_for_completion(&mcspi_dma->dma_rx_completion);
+ dma_unmap_single(mcspi->dev, xfer->rx_dma, count,
+ DMA_FROM_DEVICE);
if (mcspi->fifo_depth > 0)
return count;
if (tx != NULL) {
wait_for_completion(&mcspi_dma->dma_tx_completion);
+ dma_unmap_single(mcspi->dev, xfer->tx_dma, xfer->len,
+ DMA_TO_DEVICE);
if (mcspi->fifo_depth > 0) {
irqstat_reg = mcspi->base + OMAP2_MCSPI_IRQSTATUS;
gpio_free(spi->cs_gpio);
}
-static bool omap2_mcspi_can_dma(struct spi_master *master,
- struct spi_device *spi,
- struct spi_transfer *xfer)
-{
- if (xfer->len < DMA_MIN_BYTES)
- return false;
-
- return true;
-}
-
static int omap2_mcspi_work_one(struct omap2_mcspi *mcspi,
struct spi_device *spi, struct spi_transfer *t)
{
return -EINVAL;
}
+ if (len < DMA_MIN_BYTES)
+ goto skip_dma_map;
+
+ if (mcspi_dma->dma_tx && tx_buf != NULL) {
+ t->tx_dma = dma_map_single(mcspi->dev, (void *) tx_buf,
+ len, DMA_TO_DEVICE);
+ if (dma_mapping_error(mcspi->dev, t->tx_dma)) {
+ dev_dbg(mcspi->dev, "dma %cX %d bytes error\n",
+ 'T', len);
+ return -EINVAL;
+ }
+ }
+ if (mcspi_dma->dma_rx && rx_buf != NULL) {
+ t->rx_dma = dma_map_single(mcspi->dev, rx_buf, t->len,
+ DMA_FROM_DEVICE);
+ if (dma_mapping_error(mcspi->dev, t->rx_dma)) {
+ dev_dbg(mcspi->dev, "dma %cX %d bytes error\n",
+ 'R', len);
+ if (tx_buf != NULL)
+ dma_unmap_single(mcspi->dev, t->tx_dma,
+ len, DMA_TO_DEVICE);
+ return -EINVAL;
+ }
+ }
+
+skip_dma_map:
return omap2_mcspi_work_one(mcspi, spi, t);
}
master->transfer_one = omap2_mcspi_transfer_one;
master->set_cs = omap2_mcspi_set_cs;
master->cleanup = omap2_mcspi_cleanup;
- master->can_dma = omap2_mcspi_can_dma;
master->dev.of_node = node;
master->max_speed_hz = OMAP2_MCSPI_MAX_FREQ;
master->min_speed_hz = OMAP2_MCSPI_MAX_FREQ >> 15;
.reg_general = -1,
.reg_ssp = 0x20,
.reg_cs_ctrl = 0x24,
- .reg_capabilities = 0xfc,
+ .reg_capabilities = -1,
.rx_threshold = 1,
.tx_threshold_lo = 32,
.tx_threshold_hi = 56,
#define QSPI_FLEN(n) ((n - 1) << 0)
#define QSPI_WLEN_MAX_BITS 128
#define QSPI_WLEN_MAX_BYTES 16
+#define QSPI_WLEN_MASK QSPI_WLEN(QSPI_WLEN_MAX_BITS)
/* STATUS REGISTER */
#define BUSY 0x01
return -ETIMEDOUT;
}
-static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)
+static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t,
+ int count)
{
- int wlen, count, xfer_len;
+ int wlen, xfer_len;
unsigned int cmd;
const u8 *txbuf;
u32 data;
txbuf = t->tx_buf;
cmd = qspi->cmd | QSPI_WR_SNGL;
- count = t->len;
wlen = t->bits_per_word >> 3; /* in bytes */
xfer_len = wlen;
return 0;
}
-static int qspi_read_msg(struct ti_qspi *qspi, struct spi_transfer *t)
+static int qspi_read_msg(struct ti_qspi *qspi, struct spi_transfer *t,
+ int count)
{
- int wlen, count;
+ int wlen;
unsigned int cmd;
u8 *rxbuf;
cmd |= QSPI_RD_SNGL;
break;
}
- count = t->len;
wlen = t->bits_per_word >> 3; /* in bytes */
while (count) {
return 0;
}
-static int qspi_transfer_msg(struct ti_qspi *qspi, struct spi_transfer *t)
+static int qspi_transfer_msg(struct ti_qspi *qspi, struct spi_transfer *t,
+ int count)
{
int ret;
if (t->tx_buf) {
- ret = qspi_write_msg(qspi, t);
+ ret = qspi_write_msg(qspi, t, count);
if (ret) {
dev_dbg(qspi->dev, "Error while writing\n");
return ret;
}
if (t->rx_buf) {
- ret = qspi_read_msg(qspi, t);
+ ret = qspi_read_msg(qspi, t, count);
if (ret) {
dev_dbg(qspi->dev, "Error while reading\n");
return ret;
struct spi_device *spi = m->spi;
struct spi_transfer *t;
int status = 0, ret;
- int frame_length;
+ unsigned int frame_len_words, transfer_len_words;
+ int wlen;
/* setup device control reg */
qspi->dc = 0;
if (spi->mode & SPI_CS_HIGH)
qspi->dc |= QSPI_CSPOL(spi->chip_select);
- frame_length = (m->frame_length << 3) / spi->bits_per_word;
-
- frame_length = clamp(frame_length, 0, QSPI_FRAME);
+ frame_len_words = 0;
+ list_for_each_entry(t, &m->transfers, transfer_list)
+ frame_len_words += t->len / (t->bits_per_word >> 3);
+ frame_len_words = min_t(unsigned int, frame_len_words, QSPI_FRAME);
/* setup command reg */
qspi->cmd = 0;
qspi->cmd |= QSPI_EN_CS(spi->chip_select);
- qspi->cmd |= QSPI_FLEN(frame_length);
+ qspi->cmd |= QSPI_FLEN(frame_len_words);
ti_qspi_write(qspi, qspi->dc, QSPI_SPI_DC_REG);
ti_qspi_disable_memory_map(spi);
list_for_each_entry(t, &m->transfers, transfer_list) {
- qspi->cmd |= QSPI_WLEN(t->bits_per_word);
+ qspi->cmd = ((qspi->cmd & ~QSPI_WLEN_MASK) |
+ QSPI_WLEN(t->bits_per_word));
+
+ wlen = t->bits_per_word >> 3;
+ transfer_len_words = min(t->len / wlen, frame_len_words);
- ret = qspi_transfer_msg(qspi, t);
+ ret = qspi_transfer_msg(qspi, t, transfer_len_words * wlen);
if (ret) {
dev_dbg(qspi->dev, "transfer message failed\n");
mutex_unlock(&qspi->list_lock);
return -EINVAL;
}
- m->actual_length += t->len;
+ m->actual_length += transfer_len_words * wlen;
+ frame_len_words -= transfer_len_words;
+ if (frame_len_words == 0)
+ break;
}
mutex_unlock(&qspi->list_lock);
return retval;
}
-
-static int usb_port_prepare(struct device *dev)
-{
- return 1;
-}
#endif
static const struct dev_pm_ops usb_port_pm_ops = {
#ifdef CONFIG_PM
.runtime_suspend = usb_port_runtime_suspend,
.runtime_resume = usb_port_runtime_resume,
- .prepare = usb_port_prepare,
#endif
};
static int usb_dev_prepare(struct device *dev)
{
- struct usb_device *udev = to_usb_device(dev);
-
- /* Return 0 if the current wakeup setting is wrong, otherwise 1 */
- if (udev->do_remote_wakeup != device_may_wakeup(dev))
- return 0;
-
- return 1;
+ return 0; /* Implement eventually? */
}
static void usb_dev_complete(struct device *dev)
{
usb_phy_generic_register();
musb->xceiv = usb_get_phy(USB_PHY_TYPE_USB2);
- if (!musb->xceiv) {
+ if (IS_ERR(musb->xceiv)) {
pr_err("HS UDC: no transceiver configured\n");
- return -ENODEV;
+ return PTR_ERR(musb->xceiv);
}
/* Silicon does not implement ConfigData register.
musb_writew(epio, MUSB_RXMAXP, 0);
}
- musb_ep->desc = NULL;
- musb_ep->end_point.desc = NULL;
-
/* abort all pending DMA and requests */
nuke(musb_ep, -ESHUTDOWN);
+ musb_ep->desc = NULL;
+ musb_ep->end_point.desc = NULL;
+
schedule_work(&musb->irq_work);
spin_unlock_irqrestore(&(musb->lock), flags);
.description = "musb-hcd",
.product_desc = "MUSB HDRC host driver",
.hcd_priv_size = sizeof(struct musb *),
- .flags = HCD_USB2 | HCD_MEMORY | HCD_BH,
+ .flags = HCD_USB2 | HCD_MEMORY,
/* not using irq handler or reset hooks from usbcore, since
* those must be shared with peripheral code for OTG configs
{ USB_DEVICE(0x10C4, 0x826B) }, /* Cygnal Integrated Products, Inc., Fasttrax GPS demonstration module */
{ USB_DEVICE(0x10C4, 0x8281) }, /* Nanotec Plug & Drive */
{ USB_DEVICE(0x10C4, 0x8293) }, /* Telegesis ETRX2USB */
+ { USB_DEVICE(0x10C4, 0x82F4) }, /* Starizona MicroTouch */
{ USB_DEVICE(0x10C4, 0x82F9) }, /* Procyon AVS */
{ USB_DEVICE(0x10C4, 0x8341) }, /* Siemens MC35PU GPRS Modem */
{ USB_DEVICE(0x10C4, 0x8382) }, /* Cygnal Integrated Products, Inc. */
{ USB_DEVICE(0x10C4, 0x8418) }, /* IRZ Automation Teleport SG-10 GSM/GPRS Modem */
{ USB_DEVICE(0x10C4, 0x846E) }, /* BEI USB Sensor Interface (VCP) */
{ USB_DEVICE(0x10C4, 0x8477) }, /* Balluff RFID */
+ { USB_DEVICE(0x10C4, 0x84B6) }, /* Starizona Hyperion */
{ USB_DEVICE(0x10C4, 0x85EA) }, /* AC-Services IBUS-IF */
{ USB_DEVICE(0x10C4, 0x85EB) }, /* AC-Services CIS-IBUS */
{ USB_DEVICE(0x10C4, 0x85F8) }, /* Virtenio Preon32 */
{ USB_DEVICE(0x10C4, 0xF004) }, /* Elan Digital Systems USBcount50 */
{ USB_DEVICE(0x10C5, 0xEA61) }, /* Silicon Labs MobiData GPRS USB Modem */
{ USB_DEVICE(0x10CE, 0xEA6A) }, /* Silicon Labs MobiData GPRS USB Modem 100EU */
+ { USB_DEVICE(0x12B8, 0xEC60) }, /* Link G4 ECU */
+ { USB_DEVICE(0x12B8, 0xEC62) }, /* Link G4+ ECU */
{ USB_DEVICE(0x13AD, 0x9999) }, /* Baltech card reader */
{ USB_DEVICE(0x1555, 0x0004) }, /* Owen AC4 USB-RS485 Converter */
{ USB_DEVICE(0x166A, 0x0201) }, /* Clipsal 5500PACA C-Bus Pascal Automation Controller */
.sb = inode->i_sb,
};
lower_file = ecryptfs_file_to_lower(file);
- lower_file->f_pos = ctx->pos;
rc = iterate_dir(lower_file, &buf.ctx);
ctx->pos = buf.ctx.pos;
if (rc < 0)
}
ecryptfs_set_file_lower(
file, ecryptfs_inode_to_private(inode)->lower_file);
- if (d_is_dir(ecryptfs_dentry)) {
- ecryptfs_printk(KERN_DEBUG, "This is a directory\n");
- mutex_lock(&crypt_stat->cs_mutex);
- crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
- mutex_unlock(&crypt_stat->cs_mutex);
- rc = 0;
- goto out;
- }
rc = read_or_initialize_metadata(ecryptfs_dentry);
if (rc)
goto out_put;
return rc;
}
+/**
+ * ecryptfs_dir_open
+ * @inode: inode speciying file to open
+ * @file: Structure to return filled in
+ *
+ * Opens the file specified by inode.
+ *
+ * Returns zero on success; non-zero otherwise
+ */
+static int ecryptfs_dir_open(struct inode *inode, struct file *file)
+{
+ struct dentry *ecryptfs_dentry = file->f_path.dentry;
+ /* Private value of ecryptfs_dentry allocated in
+ * ecryptfs_lookup() */
+ struct ecryptfs_file_info *file_info;
+ struct file *lower_file;
+
+ /* Released in ecryptfs_release or end of function if failure */
+ file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
+ ecryptfs_set_file_private(file, file_info);
+ if (unlikely(!file_info)) {
+ ecryptfs_printk(KERN_ERR,
+ "Error attempting to allocate memory\n");
+ return -ENOMEM;
+ }
+ lower_file = dentry_open(ecryptfs_dentry_to_lower_path(ecryptfs_dentry),
+ file->f_flags, current_cred());
+ if (IS_ERR(lower_file)) {
+ printk(KERN_ERR "%s: Error attempting to initialize "
+ "the lower file for the dentry with name "
+ "[%pd]; rc = [%ld]\n", __func__,
+ ecryptfs_dentry, PTR_ERR(lower_file));
+ kmem_cache_free(ecryptfs_file_info_cache, file_info);
+ return PTR_ERR(lower_file);
+ }
+ ecryptfs_set_file_lower(file, lower_file);
+ return 0;
+}
+
static int ecryptfs_flush(struct file *file, fl_owner_t td)
{
struct file *lower_file = ecryptfs_file_to_lower(file);
return 0;
}
+static int ecryptfs_dir_release(struct inode *inode, struct file *file)
+{
+ fput(ecryptfs_file_to_lower(file));
+ kmem_cache_free(ecryptfs_file_info_cache,
+ ecryptfs_file_to_private(file));
+ return 0;
+}
+
+static loff_t ecryptfs_dir_llseek(struct file *file, loff_t offset, int whence)
+{
+ return vfs_llseek(ecryptfs_file_to_lower(file), offset, whence);
+}
+
static int
ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
#ifdef CONFIG_COMPAT
.compat_ioctl = ecryptfs_compat_ioctl,
#endif
- .open = ecryptfs_open,
- .flush = ecryptfs_flush,
- .release = ecryptfs_release,
+ .open = ecryptfs_dir_open,
+ .release = ecryptfs_dir_release,
.fsync = ecryptfs_fsync,
- .fasync = ecryptfs_fasync,
- .splice_read = generic_file_splice_read,
- .llseek = default_llseek,
+ .llseek = ecryptfs_dir_llseek,
};
const struct file_operations ecryptfs_main_fops = {
.llseek = generic_file_llseek,
.read_iter = ecryptfs_read_update_atime,
.write_iter = generic_file_write_iter,
- .iterate = ecryptfs_readdir,
.unlocked_ioctl = ecryptfs_unlocked_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = ecryptfs_compat_ioctl,
int retnamlen = 0;
int truncate = 0;
int ret = 0;
+ char *p;
+ int len;
if (!ISOFS_SB(inode->i_sb)->s_rock)
return 0;
rr->u.NM.flags);
break;
}
- if ((strlen(retname) + rr->len - 5) >= 254) {
+ len = rr->len - 5;
+ if (retnamlen + len >= 254) {
truncate = 1;
break;
}
- strncat(retname, rr->u.NM.name, rr->len - 5);
- retnamlen += rr->len - 5;
+ p = memchr(rr->u.NM.name, '\0', len);
+ if (unlikely(p))
+ len = p - rr->u.NM.name;
+ memcpy(retname + retnamlen, rr->u.NM.name, len);
+ retnamlen += len;
+ retname[retnamlen] = '\0';
break;
case SIG('R', 'E'):
kfree(rs.buffer);
p = buf + len + nlen;
*p = '\0';
for (kn = kn_to; kn != common; kn = kn->parent) {
- nlen = strlen(kn->name);
- p -= nlen;
- memcpy(p, kn->name, nlen);
+ size_t tmp = strlen(kn->name);
+ p -= tmp;
+ memcpy(p, kn->name, tmp);
*(--p) = '/';
}
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/namei.h>
+#include <linux/seq_file.h>
#include "kernfs-internal.h"
return 0;
}
+static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
+{
+ struct kernfs_node *node = dentry->d_fsdata;
+ struct kernfs_root *root = kernfs_root(node);
+ struct kernfs_syscall_ops *scops = root->syscall_ops;
+
+ if (scops && scops->show_path)
+ return scops->show_path(sf, node, root);
+
+ seq_dentry(sf, dentry, " \t\n\\");
+ return 0;
+}
+
const struct super_operations kernfs_sops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
.remount_fs = kernfs_sop_remount_fs,
.show_options = kernfs_sop_show_options,
+ .show_path = kernfs_sop_show_path,
};
/**
return hash_64(hash, 32);
}
+/*
+ * This is George Marsaglia's XORSHIFT generator.
+ * It implements a maximum-period LFSR in only a few
+ * instructions. It also has the property (required
+ * by hash_name()) that mix_hash(0) = 0.
+ */
+static inline unsigned long mix_hash(unsigned long hash)
+{
+ hash ^= hash << 13;
+ hash ^= hash >> 7;
+ hash ^= hash << 17;
+ return hash;
+}
+
#else /* 32-bit case */
#define fold_hash(x) (x)
+static inline unsigned long mix_hash(unsigned long hash)
+{
+ hash ^= hash << 13;
+ hash ^= hash >> 17;
+ hash ^= hash << 5;
+ return hash;
+}
+
#endif
unsigned int full_name_hash(const unsigned char *name, unsigned int len)
{
- unsigned long a, mask;
- unsigned long hash = 0;
+ unsigned long a, hash = 0;
for (;;) {
a = load_unaligned_zeropad(name);
if (len < sizeof(unsigned long))
break;
- hash += a;
- hash *= 9;
+ hash = mix_hash(hash + a);
name += sizeof(unsigned long);
len -= sizeof(unsigned long);
if (!len)
goto done;
}
- mask = bytemask_from_count(len);
- hash += mask & a;
+ hash += a & bytemask_from_count(len);
done:
return fold_hash(hash);
}
hash = a = 0;
len = -sizeof(unsigned long);
do {
- hash = (hash + a) * 9;
+ hash = mix_hash(hash + a);
len += sizeof(unsigned long);
a = load_unaligned_zeropad(name+len);
b = a ^ REPEAT_BYTE('/');
}
EXPORT_SYMBOL(vfs_path_lookup);
+/**
+ * lookup_hash - lookup single pathname component on already hashed name
+ * @name: name and hash to lookup
+ * @base: base directory to lookup from
+ *
+ * The name must have been verified and hashed (see lookup_one_len()). Using
+ * this after just full_name_hash() is unsafe.
+ *
+ * This function also doesn't check for search permission on base directory.
+ *
+ * Use lookup_one_len_unlocked() instead, unless you really know what you are
+ * doing.
+ *
+ * Do not hold i_mutex; this helper takes i_mutex if necessary.
+ */
+struct dentry *lookup_hash(const struct qstr *name, struct dentry *base)
+{
+ struct dentry *ret;
+
+ ret = lookup_dcache(name, base, 0);
+ if (!ret)
+ ret = lookup_slow(name, base, 0);
+
+ return ret;
+}
+EXPORT_SYMBOL(lookup_hash);
+
/**
* lookup_one_len - filesystem helper to lookup single pathname component
* @name: pathname component to lookup
struct qstr this;
unsigned int c;
int err;
- struct dentry *ret;
this.name = name;
this.len = len;
if (err)
return ERR_PTR(err);
- ret = lookup_dcache(&this, base, 0);
- if (!ret)
- ret = lookup_slow(&this, base, 0);
- return ret;
+ return lookup_hash(&this, base);
}
EXPORT_SYMBOL(lookup_one_len_unlocked);
dentry = lookup_real(dir, dentry, nd->flags);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
-
- if (create_error) {
- int open_flag = op->open_flag;
-
- error = create_error;
- if ((open_flag & O_EXCL)) {
- if (!dentry->d_inode)
- goto out;
- } else if (!dentry->d_inode) {
- goto out;
- } else if ((open_flag & O_TRUNC) &&
- d_is_reg(dentry)) {
- goto out;
- }
- /* will fail later, go on to get the right error */
- }
+ }
+ if (create_error && !dentry->d_inode) {
+ error = create_error;
+ goto out;
}
looked_up:
path->dentry = dentry;
bool new_is_dir = false;
unsigned max_links = new_dir->i_sb->s_max_links;
- if (source == target)
+ /*
+ * Check source == target.
+ * On overlayfs need to look at underlying inodes.
+ */
+ if (vfs_select_inode(old_dentry, 0) == vfs_select_inode(new_dentry, 0))
return 0;
error = may_delete(old_dir, old_dentry, is_dir);
brelse(di_bh);
return acl;
}
+
+int ocfs2_acl_chmod(struct inode *inode, struct buffer_head *bh)
+{
+ struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+ struct posix_acl *acl;
+ int ret;
+
+ if (S_ISLNK(inode->i_mode))
+ return -EOPNOTSUPP;
+
+ if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
+ return 0;
+
+ acl = ocfs2_get_acl_nolock(inode, ACL_TYPE_ACCESS, bh);
+ if (IS_ERR(acl) || !acl)
+ return PTR_ERR(acl);
+ ret = __posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
+ if (ret)
+ return ret;
+ ret = ocfs2_set_acl(NULL, inode, NULL, ACL_TYPE_ACCESS,
+ acl, NULL, NULL);
+ posix_acl_release(acl);
+ return ret;
+}
+
+/*
+ * Initialize the ACLs of a new inode. If parent directory has default ACL,
+ * then clone to new inode. Called from ocfs2_mknod.
+ */
+int ocfs2_init_acl(handle_t *handle,
+ struct inode *inode,
+ struct inode *dir,
+ struct buffer_head *di_bh,
+ struct buffer_head *dir_bh,
+ struct ocfs2_alloc_context *meta_ac,
+ struct ocfs2_alloc_context *data_ac)
+{
+ struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+ struct posix_acl *acl = NULL;
+ int ret = 0, ret2;
+ umode_t mode;
+
+ if (!S_ISLNK(inode->i_mode)) {
+ if (osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) {
+ acl = ocfs2_get_acl_nolock(dir, ACL_TYPE_DEFAULT,
+ dir_bh);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ }
+ if (!acl) {
+ mode = inode->i_mode & ~current_umask();
+ ret = ocfs2_acl_set_mode(inode, di_bh, handle, mode);
+ if (ret) {
+ mlog_errno(ret);
+ goto cleanup;
+ }
+ }
+ }
+ if ((osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) && acl) {
+ if (S_ISDIR(inode->i_mode)) {
+ ret = ocfs2_set_acl(handle, inode, di_bh,
+ ACL_TYPE_DEFAULT, acl,
+ meta_ac, data_ac);
+ if (ret)
+ goto cleanup;
+ }
+ mode = inode->i_mode;
+ ret = __posix_acl_create(&acl, GFP_NOFS, &mode);
+ if (ret < 0)
+ return ret;
+
+ ret2 = ocfs2_acl_set_mode(inode, di_bh, handle, mode);
+ if (ret2) {
+ mlog_errno(ret2);
+ ret = ret2;
+ goto cleanup;
+ }
+ if (ret > 0) {
+ ret = ocfs2_set_acl(handle, inode,
+ di_bh, ACL_TYPE_ACCESS,
+ acl, meta_ac, data_ac);
+ }
+ }
+cleanup:
+ posix_acl_release(acl);
+ return ret;
+}
struct posix_acl *acl,
struct ocfs2_alloc_context *meta_ac,
struct ocfs2_alloc_context *data_ac);
+extern int ocfs2_acl_chmod(struct inode *, struct buffer_head *);
+extern int ocfs2_init_acl(handle_t *, struct inode *, struct inode *,
+ struct buffer_head *, struct buffer_head *,
+ struct ocfs2_alloc_context *,
+ struct ocfs2_alloc_context *);
#endif /* OCFS2_ACL_H */
if (size_change)
ocfs2_rw_unlock(inode, 1);
bail:
- brelse(bh);
/* Release quota pointers in case we acquired them */
for (qtype = 0; qtype < OCFS2_MAXQUOTAS; qtype++)
dqput(transfer_to[qtype]);
if (!status && attr->ia_valid & ATTR_MODE) {
- status = posix_acl_chmod(inode, inode->i_mode);
+ status = ocfs2_acl_chmod(inode, bh);
if (status < 0)
mlog_errno(status);
}
if (inode_locked)
ocfs2_inode_unlock(inode, 1);
+ brelse(bh);
return status;
}
struct ocfs2_dir_lookup_result lookup = { NULL, };
sigset_t oldset;
int did_block_signals = 0;
- struct posix_acl *default_acl = NULL, *acl = NULL;
struct ocfs2_dentry_lock *dl = NULL;
trace_ocfs2_mknod(dir, dentry, dentry->d_name.len, dentry->d_name.name,
goto leave;
}
- status = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
- if (status) {
- mlog_errno(status);
- goto leave;
- }
-
handle = ocfs2_start_trans(osb, ocfs2_mknod_credits(osb->sb,
S_ISDIR(mode),
xattr_credits));
inc_nlink(dir);
}
- if (default_acl) {
- status = ocfs2_set_acl(handle, inode, new_fe_bh,
- ACL_TYPE_DEFAULT, default_acl,
- meta_ac, data_ac);
- }
- if (!status && acl) {
- status = ocfs2_set_acl(handle, inode, new_fe_bh,
- ACL_TYPE_ACCESS, acl,
- meta_ac, data_ac);
- }
+ status = ocfs2_init_acl(handle, inode, dir, new_fe_bh, parent_fe_bh,
+ meta_ac, data_ac);
if (status < 0) {
mlog_errno(status);
d_instantiate(dentry, inode);
status = 0;
leave:
- if (default_acl)
- posix_acl_release(default_acl);
- if (acl)
- posix_acl_release(acl);
if (status < 0 && did_quota_inode)
dquot_free_inode(inode);
if (handle)
struct inode *inode = d_inode(old_dentry);
struct buffer_head *old_bh = NULL;
struct inode *new_orphan_inode = NULL;
- struct posix_acl *default_acl, *acl;
- umode_t mode;
if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb)))
return -EOPNOTSUPP;
- mode = inode->i_mode;
- error = posix_acl_create(dir, &mode, &default_acl, &acl);
- if (error) {
- mlog_errno(error);
- return error;
- }
- error = ocfs2_create_inode_in_orphan(dir, mode,
+ error = ocfs2_create_inode_in_orphan(dir, inode->i_mode,
&new_orphan_inode);
if (error) {
mlog_errno(error);
/* If the security isn't preserved, we need to re-initialize them. */
if (!preserve) {
error = ocfs2_init_security_and_acl(dir, new_orphan_inode,
- &new_dentry->d_name,
- default_acl, acl);
+ &new_dentry->d_name);
if (error)
mlog_errno(error);
}
out:
- if (default_acl)
- posix_acl_release(default_acl);
- if (acl)
- posix_acl_release(acl);
if (!error) {
error = ocfs2_mv_orphaned_inode_to_new(dir, new_orphan_inode,
new_dentry);
*/
int ocfs2_init_security_and_acl(struct inode *dir,
struct inode *inode,
- const struct qstr *qstr,
- struct posix_acl *default_acl,
- struct posix_acl *acl)
+ const struct qstr *qstr)
{
- struct buffer_head *dir_bh = NULL;
int ret = 0;
+ struct buffer_head *dir_bh = NULL;
ret = ocfs2_init_security_get(inode, dir, qstr, NULL);
if (ret) {
mlog_errno(ret);
goto leave;
}
-
- if (!ret && default_acl)
- ret = ocfs2_iop_set_acl(inode, default_acl, ACL_TYPE_DEFAULT);
- if (!ret && acl)
- ret = ocfs2_iop_set_acl(inode, acl, ACL_TYPE_ACCESS);
+ ret = ocfs2_init_acl(NULL, inode, dir, NULL, dir_bh, NULL, NULL);
+ if (ret)
+ mlog_errno(ret);
ocfs2_inode_unlock(dir, 0);
brelse(dir_bh);
bool preserve_security);
int ocfs2_init_security_and_acl(struct inode *dir,
struct inode *inode,
- const struct qstr *qstr,
- struct posix_acl *default_acl,
- struct posix_acl *acl);
+ const struct qstr *qstr);
#endif /* OCFS2_XATTR_H */
int vfs_open(const struct path *path, struct file *file,
const struct cred *cred)
{
- struct dentry *dentry = path->dentry;
- struct inode *inode = dentry->d_inode;
+ struct inode *inode = vfs_select_inode(path->dentry, file->f_flags);
- file->f_path = *path;
- if (dentry->d_flags & DCACHE_OP_SELECT_INODE) {
- inode = dentry->d_op->d_select_inode(dentry, file->f_flags);
- if (IS_ERR(inode))
- return PTR_ERR(inode);
- }
+ if (IS_ERR(inode))
+ return PTR_ERR(inode);
+ file->f_path = *path;
return do_dentry_open(file, inode, NULL, cred);
}
{
struct dentry *dentry;
- inode_lock(dir->d_inode);
- dentry = lookup_one_len(name->name, dir, name->len);
- inode_unlock(dir->d_inode);
+ dentry = lookup_hash(name, dir);
if (IS_ERR(dentry)) {
if (PTR_ERR(dentry) == -ENOENT)
&& !lookup_symbol_name(wchan, symname))
seq_printf(m, "%s", symname);
else
- seq_puts(m, "0\n");
+ seq_putc(m, '0');
return 0;
}
if (unlikely(ret < 0))
return ret;
+ if (unlikely(len > MAX_RW_COUNT))
+ len = MAX_RW_COUNT;
+
if (in->f_op->splice_read)
splice_read = in->f_op->splice_read;
else
#define __HAVE_BUILTIN_BSWAP32__
#define __HAVE_BUILTIN_BSWAP64__
#endif
-#if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600)
+#if GCC_VERSION >= 40800
#define __HAVE_BUILTIN_BSWAP16__
#endif
#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
return dentry;
}
+static inline struct inode *vfs_select_inode(struct dentry *dentry,
+ unsigned open_flags)
+{
+ struct inode *inode = d_inode(dentry);
+
+ if (inode && unlikely(dentry->d_flags & DCACHE_OP_SELECT_INODE))
+ inode = dentry->d_op->d_select_inode(dentry, open_flags);
+
+ return inode;
+}
+
+
#endif /* __LINUX_DCACHE_H */
int (*rmdir)(struct kernfs_node *kn);
int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
const char *new_name);
+ int (*show_path)(struct seq_file *sf, struct kernfs_node *kn,
+ struct kernfs_root *root);
};
struct kernfs_root {
#define S2MPS11_LDO_VSEL_MASK 0x3F
#define S2MPS11_BUCK_VSEL_MASK 0xFF
+#define S2MPS11_BUCK9_VSEL_MASK 0x1F
#define S2MPS11_ENABLE_MASK (0x03 << S2MPS11_ENABLE_SHIFT)
#define S2MPS11_ENABLE_SHIFT 0x06
#define S2MPS11_LDO_N_VOLTAGES (S2MPS11_LDO_VSEL_MASK + 1)
#define S2MPS11_BUCK_N_VOLTAGES (S2MPS11_BUCK_VSEL_MASK + 1)
+#define S2MPS11_BUCK9_N_VOLTAGES (S2MPS11_BUCK9_VSEL_MASK + 1)
#define S2MPS11_RAMP_DELAY 25000 /* uV/us */
#define S2MPS11_CTRL1_PWRHOLD_MASK BIT(4)
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int total_mapcount(struct page *page);
+int page_trans_huge_mapcount(struct page *page, int *total_mapcount);
#else
static inline int total_mapcount(struct page *page)
{
return page_mapcount(page);
}
+static inline int page_trans_huge_mapcount(struct page *page,
+ int *total_mapcount)
+{
+ int mapcount = page_mapcount(page);
+ if (total_mapcount)
+ *total_mapcount = mapcount;
+ return mapcount;
+}
#endif
static inline struct page *virt_to_head_page(const void *x)
extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
+struct qstr;
+extern struct dentry *lookup_hash(const struct qstr *, struct dentry *);
extern int follow_down_one(struct path *);
extern int follow_down(struct path *);
struct udp_offload;
+/* 'skb->encapsulation' is set before gro_complete() is called. gro_complete()
+ * must set 'skb->inner_mac_header' to the beginning of tunnel payload.
+ */
struct udp_offload_callbacks {
struct sk_buff **(*gro_receive)(struct sk_buff **head,
struct sk_buff *skb,
+++ /dev/null
-/*
- * FLoating proportions
- *
- * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
- *
- * This file contains the public data structure and API definitions.
- */
-
-#ifndef _LINUX_PROPORTIONS_H
-#define _LINUX_PROPORTIONS_H
-
-#include <linux/percpu_counter.h>
-#include <linux/spinlock.h>
-#include <linux/mutex.h>
-#include <linux/gfp.h>
-
-struct prop_global {
- /*
- * The period over which we differentiate
- *
- * period = 2^shift
- */
- int shift;
- /*
- * The total event counter aka 'time'.
- *
- * Treated as an unsigned long; the lower 'shift - 1' bits are the
- * counter bits, the remaining upper bits the period counter.
- */
- struct percpu_counter events;
-};
-
-/*
- * global proportion descriptor
- *
- * this is needed to consistently flip prop_global structures.
- */
-struct prop_descriptor {
- int index;
- struct prop_global pg[2];
- struct mutex mutex; /* serialize the prop_global switch */
-};
-
-int prop_descriptor_init(struct prop_descriptor *pd, int shift, gfp_t gfp);
-void prop_change_shift(struct prop_descriptor *pd, int new_shift);
-
-/*
- * ----- PERCPU ------
- */
-
-struct prop_local_percpu {
- /*
- * the local events counter
- */
- struct percpu_counter events;
-
- /*
- * snapshot of the last seen global state
- */
- int shift;
- unsigned long period;
- raw_spinlock_t lock; /* protect the snapshot state */
-};
-
-int prop_local_init_percpu(struct prop_local_percpu *pl, gfp_t gfp);
-void prop_local_destroy_percpu(struct prop_local_percpu *pl);
-void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl);
-void prop_fraction_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl,
- long *numerator, long *denominator);
-
-static inline
-void prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- __prop_inc_percpu(pd, pl);
- local_irq_restore(flags);
-}
-
-/*
- * Limit the time part in order to ensure there are some bits left for the
- * cycle counter and fraction multiply.
- */
-#if BITS_PER_LONG == 32
-#define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
-#else
-#define PROP_MAX_SHIFT (BITS_PER_LONG/2)
-#endif
-
-#define PROP_FRAC_SHIFT (BITS_PER_LONG - PROP_MAX_SHIFT - 1)
-#define PROP_FRAC_BASE (1UL << PROP_FRAC_SHIFT)
-
-void __prop_inc_percpu_max(struct prop_descriptor *pd,
- struct prop_local_percpu *pl, long frac);
-
-
-/*
- * ----- SINGLE ------
- */
-
-struct prop_local_single {
- /*
- * the local events counter
- */
- unsigned long events;
-
- /*
- * snapshot of the last seen global state
- * and a lock protecting this state
- */
- unsigned long period;
- int shift;
- raw_spinlock_t lock; /* protect the snapshot state */
-};
-
-#define INIT_PROP_LOCAL_SINGLE(name) \
-{ .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \
-}
-
-int prop_local_init_single(struct prop_local_single *pl);
-void prop_local_destroy_single(struct prop_local_single *pl);
-void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
-void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
- long *numerator, long *denominator);
-
-static inline
-void prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- __prop_inc_single(pd, pl);
- local_irq_restore(flags);
-}
-
-#endif /* _LINUX_PROPORTIONS_H */
* CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
* critical section unless it can prove otherwise.
*/
-#ifdef CONFIG_PREEMPT_COUNT
int rcu_read_lock_sched_held(void);
-#else /* #ifdef CONFIG_PREEMPT_COUNT */
-static inline int rcu_read_lock_sched_held(void)
-{
- return 1;
-}
-#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
return 1;
}
-#ifdef CONFIG_PREEMPT_COUNT
static inline int rcu_read_lock_sched_held(void)
{
- return preempt_count() != 0 || irqs_disabled();
-}
-#else /* #ifdef CONFIG_PREEMPT_COUNT */
-static inline int rcu_read_lock_sched_held(void)
-{
- return 1;
+ return !preemptible();
}
-#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */
-
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
#ifdef CONFIG_PROVE_RCU
#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
+/*
+ * Dump the ftrace buffer, but only one time per callsite per boot.
+ */
+#define rcu_ftrace_dump(oops_dump_mode) \
+do { \
+ static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \
+ \
+ if (!atomic_read(&___rfd_beenhere) && \
+ !atomic_xchg(&___rfd_beenhere, 1)) \
+ ftrace_dump(oops_dump_mode); \
+} while (0)
+
+
#endif /* __LINUX_RCUPDATE_H */
return 0;
}
+/*
+ * Return the number of expedited grace periods completed.
+ */
+static inline unsigned long rcu_exp_batches_completed(void)
+{
+ return 0;
+}
+
+/*
+ * Return the number of expedited sched grace periods completed.
+ */
+static inline unsigned long rcu_exp_batches_completed_sched(void)
+{
+ return 0;
+}
+
static inline void rcu_force_quiescent_state(void)
{
}
unsigned long rcu_batches_completed(void);
unsigned long rcu_batches_completed_bh(void);
unsigned long rcu_batches_completed_sched(void);
+unsigned long rcu_exp_batches_completed(void);
+unsigned long rcu_exp_batches_completed_sched(void);
void show_rcu_gp_kthreads(void);
void rcu_force_quiescent_state(void);
#include <linux/pid.h>
#include <linux/percpu.h>
#include <linux/topology.h>
-#include <linux/proportions.h>
#include <linux/seccomp.h>
#include <linux/rcupdate.h>
#include <linux/rculist.h>
unsigned long sas_ss_sp;
size_t sas_ss_size;
+ unsigned sas_ss_flags;
struct callback_head *task_works;
*/
static inline int on_sig_stack(unsigned long sp)
{
+ /*
+ * If the signal stack is SS_AUTODISARM then, by construction, we
+ * can't be on the signal stack unless user code deliberately set
+ * SS_AUTODISARM when we were already on it.
+ *
+ * This improves reliability: if user state gets corrupted such that
+ * the stack pointer points very close to the end of the signal stack,
+ * then this check will enable the signal to be handled anyway.
+ */
+ if (current->sas_ss_flags & SS_AUTODISARM)
+ return 0;
+
#ifdef CONFIG_STACK_GROWSUP
return sp >= current->sas_ss_sp &&
sp - current->sas_ss_sp < current->sas_ss_size;
return on_sig_stack(sp) ? SS_ONSTACK : 0;
}
+static inline void sas_ss_reset(struct task_struct *p)
+{
+ p->sas_ss_sp = 0;
+ p->sas_ss_size = 0;
+ p->sas_ss_flags = SS_DISABLE;
+}
+
static inline unsigned long sigsp(unsigned long sp, struct ksignal *ksig)
{
if (unlikely((ksig->ka.sa.sa_flags & SA_ONSTACK)) && ! sas_ss_flags(sp))
stack_t __user *__uss = uss; \
struct task_struct *t = current; \
put_user_ex((void __user *)t->sas_ss_sp, &__uss->ss_sp); \
- put_user_ex(sas_ss_flags(sp), &__uss->ss_flags); \
+ put_user_ex(t->sas_ss_flags, &__uss->ss_flags); \
put_user_ex(t->sas_ss_size, &__uss->ss_size); \
+ if (t->sas_ss_flags & SS_AUTODISARM) \
+ sas_ss_reset(t); \
} while (0);
#ifdef CONFIG_PROC_FS
extern int page_swapcount(struct page *);
extern int swp_swapcount(swp_entry_t entry);
extern struct swap_info_struct *page_swap_info(struct page *);
-extern int reuse_swap_page(struct page *);
+extern bool reuse_swap_page(struct page *, int *);
extern int try_to_free_swap(struct page *);
struct backing_dev_info;
return 0;
}
-#define reuse_swap_page(page) \
- (!PageTransCompound(page) && page_mapcount(page) == 1)
+#define reuse_swap_page(page, total_mapcount) \
+ (page_trans_huge_mapcount(page, total_mapcount) == 1)
static inline int try_to_free_swap(struct page *page)
{
size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
size_t iov_iter_zero(size_t bytes, struct iov_iter *);
unsigned long iov_iter_alignment(const struct iov_iter *i);
+unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
unsigned long nr_segs, size_t count);
void iov_iter_kvec(struct iov_iter *i, int direction, const struct kvec *kvec,
struct flow_cache flow_cache_global;
atomic_t flow_cache_genid;
struct list_head flow_cache_gc_list;
+ atomic_t flow_cache_gc_count;
spinlock_t flow_cache_gc_lock;
struct work_struct flow_cache_gc_work;
struct work_struct flow_cache_flush_work;
return iptunnel_handle_offloads(skb, type);
}
-static inline void udp_tunnel_gro_complete(struct sk_buff *skb, int nhoff)
-{
- struct udphdr *uh;
-
- uh = (struct udphdr *)(skb->data + nhoff - sizeof(struct udphdr));
- skb_shinfo(skb)->gso_type |= uh->check ?
- SKB_GSO_UDP_TUNNEL_CSUM : SKB_GSO_UDP_TUNNEL;
-}
-
static inline void udp_tunnel_encap_enable(struct socket *sock)
{
#if IS_ENABLED(CONFIG_IPV6)
__entry->grplo, __entry->grphi, __entry->qsmask)
);
+/*
+ * Tracepoint for expedited grace-period events. Takes a string identifying
+ * the RCU flavor, the expedited grace-period sequence number, and a string
+ * identifying the grace-period-related event as follows:
+ *
+ * "snap": Captured snapshot of expedited grace period sequence number.
+ * "start": Started a real expedited grace period.
+ * "end": Ended a real expedited grace period.
+ * "endwake": Woke piggybackers up.
+ * "done": Someone else did the expedited grace period for us.
+ */
+TRACE_EVENT(rcu_exp_grace_period,
+
+ TP_PROTO(const char *rcuname, unsigned long gpseq, const char *gpevent),
+
+ TP_ARGS(rcuname, gpseq, gpevent),
+
+ TP_STRUCT__entry(
+ __field(const char *, rcuname)
+ __field(unsigned long, gpseq)
+ __field(const char *, gpevent)
+ ),
+
+ TP_fast_assign(
+ __entry->rcuname = rcuname;
+ __entry->gpseq = gpseq;
+ __entry->gpevent = gpevent;
+ ),
+
+ TP_printk("%s %lu %s",
+ __entry->rcuname, __entry->gpseq, __entry->gpevent)
+);
+
+/*
+ * Tracepoint for expedited grace-period funnel-locking events. Takes a
+ * string identifying the RCU flavor, an integer identifying the rcu_node
+ * combining-tree level, another pair of integers identifying the lowest-
+ * and highest-numbered CPU associated with the current rcu_node structure,
+ * and a string. identifying the grace-period-related event as follows:
+ *
+ * "nxtlvl": Advance to next level of rcu_node funnel
+ * "wait": Wait for someone else to do expedited GP
+ */
+TRACE_EVENT(rcu_exp_funnel_lock,
+
+ TP_PROTO(const char *rcuname, u8 level, int grplo, int grphi,
+ const char *gpevent),
+
+ TP_ARGS(rcuname, level, grplo, grphi, gpevent),
+
+ TP_STRUCT__entry(
+ __field(const char *, rcuname)
+ __field(u8, level)
+ __field(int, grplo)
+ __field(int, grphi)
+ __field(const char *, gpevent)
+ ),
+
+ TP_fast_assign(
+ __entry->rcuname = rcuname;
+ __entry->level = level;
+ __entry->grplo = grplo;
+ __entry->grphi = grphi;
+ __entry->gpevent = gpevent;
+ ),
+
+ TP_printk("%s %d %d %d %s",
+ __entry->rcuname, __entry->level, __entry->grplo,
+ __entry->grphi, __entry->gpevent)
+);
+
/*
* Tracepoint for RCU no-CBs CPU callback handoffs. This event is intended
* to assist debugging of these handoffs.
#else /* #ifdef CONFIG_RCU_TRACE */
#define trace_rcu_grace_period(rcuname, gpnum, gpevent) do { } while (0)
-#define trace_rcu_grace_period_init(rcuname, gpnum, level, grplo, grphi, \
- qsmask) do { } while (0)
#define trace_rcu_future_grace_period(rcuname, gpnum, completed, c, \
level, grplo, grphi, event) \
do { } while (0)
+#define trace_rcu_grace_period_init(rcuname, gpnum, level, grplo, grphi, \
+ qsmask) do { } while (0)
+#define trace_rcu_exp_grace_period(rcuname, gqseq, gpevent) \
+ do { } while (0)
+#define trace_rcu_exp_funnel_lock(rcuname, level, grplo, grphi, gpevent) \
+ do { } while (0)
#define trace_rcu_nocb_wake(rcuname, cpu, reason) do { } while (0)
#define trace_rcu_preempt_task(rcuname, pid, gpnum) do { } while (0)
#define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0)
#ifndef _LINUX_IF_H
#define _LINUX_IF_H
+#include <linux/libc-compat.h> /* for compatibility with glibc */
#include <linux/types.h> /* for "__kernel_caddr_t" et al */
#include <linux/socket.h> /* for "struct sockaddr" et al */
#include <linux/compiler.h> /* for "__user" et al */
+#if __UAPI_DEF_IF_IFNAMSIZ
#define IFNAMSIZ 16
+#endif /* __UAPI_DEF_IF_IFNAMSIZ */
#define IFALIASZ 256
#include <linux/hdlc/ioctl.h>
+/* For glibc compatibility. An empty enum does not compile. */
+#if __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO != 0 && \
+ __UAPI_DEF_IF_NET_DEVICE_FLAGS != 0
/**
* enum net_device_flags - &struct net_device flags
*
* @IFF_ECHO: echo sent packets. Volatile.
*/
enum net_device_flags {
+/* for compatibility with glibc net/if.h */
+#if __UAPI_DEF_IF_NET_DEVICE_FLAGS
IFF_UP = 1<<0, /* sysfs */
IFF_BROADCAST = 1<<1, /* volatile */
IFF_DEBUG = 1<<2, /* sysfs */
IFF_PORTSEL = 1<<13, /* sysfs */
IFF_AUTOMEDIA = 1<<14, /* sysfs */
IFF_DYNAMIC = 1<<15, /* sysfs */
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS */
+#if __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
IFF_LOWER_UP = 1<<16, /* volatile */
IFF_DORMANT = 1<<17, /* volatile */
IFF_ECHO = 1<<18, /* volatile */
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
};
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO != 0 && __UAPI_DEF_IF_NET_DEVICE_FLAGS != 0 */
+/* for compatibility with glibc net/if.h */
+#if __UAPI_DEF_IF_NET_DEVICE_FLAGS
#define IFF_UP IFF_UP
#define IFF_BROADCAST IFF_BROADCAST
#define IFF_DEBUG IFF_DEBUG
#define IFF_PORTSEL IFF_PORTSEL
#define IFF_AUTOMEDIA IFF_AUTOMEDIA
#define IFF_DYNAMIC IFF_DYNAMIC
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS */
+
+#if __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
#define IFF_LOWER_UP IFF_LOWER_UP
#define IFF_DORMANT IFF_DORMANT
#define IFF_ECHO IFF_ECHO
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
#define IFF_VOLATILE (IFF_LOOPBACK|IFF_POINTOPOINT|IFF_BROADCAST|IFF_ECHO|\
IFF_MASTER|IFF_SLAVE|IFF_RUNNING|IFF_LOWER_UP|IFF_DORMANT)
* being very small might be worth keeping for clean configuration.
*/
+/* for compatibility with glibc net/if.h */
+#if __UAPI_DEF_IF_IFMAP
struct ifmap {
unsigned long mem_start;
unsigned long mem_end;
unsigned char port;
/* 3 bytes spare */
};
+#endif /* __UAPI_DEF_IF_IFMAP */
struct if_settings {
unsigned int type; /* Type of physical device or protocol */
* remainder may be interface specific.
*/
+/* for compatibility with glibc net/if.h */
+#if __UAPI_DEF_IF_IFREQ
struct ifreq {
#define IFHWADDRLEN 6
union
struct if_settings ifru_settings;
} ifr_ifru;
};
+#endif /* __UAPI_DEF_IF_IFREQ */
#define ifr_name ifr_ifrn.ifrn_name /* interface name */
#define ifr_hwaddr ifr_ifru.ifru_hwaddr /* MAC address */
* must know all networks accessible).
*/
+/* for compatibility with glibc net/if.h */
+#if __UAPI_DEF_IF_IFCONF
struct ifconf {
int ifc_len; /* size of buffer */
union {
struct ifreq __user *ifcu_req;
} ifc_ifcu;
};
+#endif /* __UAPI_DEF_IF_IFCONF */
+
#define ifc_buf ifc_ifcu.ifcu_buf /* buffer address */
#define ifc_req ifc_ifcu.ifcu_req /* array of structures */
#define MACSEC_MAX_KEY_LEN 128
+#define MACSEC_KEYID_LEN 16
+
#define MACSEC_DEFAULT_CIPHER_ID 0x0080020001000001ULL
#define MACSEC_DEFAULT_CIPHER_ALT 0x0080C20001000001ULL
MACSEC_SA_ATTR_ACTIVE, /* config/dump, u8 0..1 */
MACSEC_SA_ATTR_PN, /* config/dump, u32 */
MACSEC_SA_ATTR_KEY, /* config, data */
- MACSEC_SA_ATTR_KEYID, /* config/dump, u64 */
+ MACSEC_SA_ATTR_KEYID, /* config/dump, 128-bit */
MACSEC_SA_ATTR_STATS, /* dump, nested, macsec_sa_stats_attr */
__MACSEC_SA_ATTR_END,
NUM_MACSEC_SA_ATTR = __MACSEC_SA_ATTR_END,
/* We have included glibc headers... */
#if defined(__GLIBC__)
+/* Coordinate with glibc net/if.h header. */
+#if defined(_NET_IF_H)
+
+/* GLIBC headers included first so don't define anything
+ * that would already be defined. */
+
+#define __UAPI_DEF_IF_IFCONF 0
+#define __UAPI_DEF_IF_IFMAP 0
+#define __UAPI_DEF_IF_IFNAMSIZ 0
+#define __UAPI_DEF_IF_IFREQ 0
+/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 0
+/* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
+#ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
+#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
+
+#else /* _NET_IF_H */
+
+/* Linux headers included first, and we must define everything
+ * we need. The expectation is that glibc will check the
+ * __UAPI_DEF_* defines and adjust appropriately. */
+
+#define __UAPI_DEF_IF_IFCONF 1
+#define __UAPI_DEF_IF_IFMAP 1
+#define __UAPI_DEF_IF_IFNAMSIZ 1
+#define __UAPI_DEF_IF_IFREQ 1
+/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
+/* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
+
+#endif /* _NET_IF_H */
+
/* Coordinate with glibc netinet/in.h header. */
#if defined(_NETINET_IN_H)
* that we need. */
#else /* !defined(__GLIBC__) */
+/* Definitions for if.h */
+#define __UAPI_DEF_IF_IFCONF 1
+#define __UAPI_DEF_IF_IFMAP 1
+#define __UAPI_DEF_IF_IFNAMSIZ 1
+#define __UAPI_DEF_IF_IFREQ 1
+/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
+/* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
+#define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
+
/* Definitions for in.h */
#define __UAPI_DEF_IN_ADDR 1
#define __UAPI_DEF_IN_IPPROTO 1
#define SS_ONSTACK 1
#define SS_DISABLE 2
+/* bit-flags */
+#define SS_AUTODISARM (1U << 31) /* disable sas during sighandling */
+/* mask for all SS_xxx flags */
+#define SS_FLAG_BITS SS_AUTODISARM
+
#endif /* _UAPI_LINUX_SIGNAL_H */
header-y += tc_vlan.h
header-y += tc_bpf.h
header-y += tc_connmark.h
+header-y += tc_ife.h
cgroup_free_root(root);
}
+/*
+ * look up cgroup associated with current task's cgroup namespace on the
+ * specified hierarchy
+ */
+static struct cgroup *
+current_cgns_cgroup_from_root(struct cgroup_root *root)
+{
+ struct cgroup *res = NULL;
+ struct css_set *cset;
+
+ lockdep_assert_held(&css_set_lock);
+
+ rcu_read_lock();
+
+ cset = current->nsproxy->cgroup_ns->root_cset;
+ if (cset == &init_css_set) {
+ res = &root->cgrp;
+ } else {
+ struct cgrp_cset_link *link;
+
+ list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
+ struct cgroup *c = link->cgrp;
+
+ if (c->root == root) {
+ res = c;
+ break;
+ }
+ }
+ }
+ rcu_read_unlock();
+
+ BUG_ON(!res);
+ return res;
+}
+
/* look up cgroup associated with given css_set on the specified hierarchy */
static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
struct cgroup_root *root)
return 0;
}
+static int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
+ struct kernfs_root *kf_root)
+{
+ int len = 0;
+ char *buf = NULL;
+ struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
+ struct cgroup *ns_cgroup;
+
+ buf = kmalloc(PATH_MAX, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ spin_lock_bh(&css_set_lock);
+ ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
+ len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
+ spin_unlock_bh(&css_set_lock);
+
+ if (len >= PATH_MAX)
+ len = -ERANGE;
+ else if (len > 0) {
+ seq_escape(sf, buf, " \t\n\\");
+ len = 0;
+ }
+ kfree(buf);
+ return len;
+}
+
static int cgroup_show_options(struct seq_file *seq,
struct kernfs_root *kf_root)
{
.mkdir = cgroup_mkdir,
.rmdir = cgroup_rmdir,
.rename = cgroup_rename,
+ .show_path = cgroup_show_path,
};
static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
* 1 - disallow cpu events for unpriv
* 2 - disallow kernel profiling for unpriv
*/
-int sysctl_perf_event_paranoid __read_mostly = 1;
+int sysctl_perf_event_paranoid __read_mostly = 2;
/* Minimum for 512 kiB + 1 user control page */
int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */
bool truncated)
{
struct ring_buffer *rb = handle->rb;
+ bool wakeup = truncated;
unsigned long aux_head;
u64 flags = 0;
aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);
if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {
- perf_output_wakeup(handle);
+ wakeup = true;
local_add(rb->aux_watermark, &rb->aux_wakeup);
}
+
+ if (wakeup) {
+ if (truncated)
+ handle->event->pending_disable = 1;
+ perf_output_wakeup(handle);
+ }
+
handle->event = NULL;
local_set(&rb->aux_nest, 0);
* sigaltstack should be cleared when sharing the same VM
*/
if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
- p->sas_ss_sp = p->sas_ss_size = 0;
+ sas_ss_reset(p);
/*
* Syscall tracing and stepping should be turned off in the
obj-y += update.o sync.o
obj-$(CONFIG_SRCU) += srcu.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
+obj-$(CONFIG_RCU_PERF_TEST) += rcuperf.o
obj-$(CONFIG_TREE_RCU) += tree.o
obj-$(CONFIG_PREEMPT_RCU) += tree.o
obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.o
--- /dev/null
+/*
+ * Read-Copy Update module-based performance-test facility
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, you can access it online at
+ * http://www.gnu.org/licenses/gpl-2.0.html.
+ *
+ * Copyright (C) IBM Corporation, 2015
+ *
+ * Authors: Paul E. McKenney <paulmck@us.ibm.com>
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/atomic.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/reboot.h>
+#include <linux/freezer.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
+#include <linux/stat.h>
+#include <linux/srcu.h>
+#include <linux/slab.h>
+#include <asm/byteorder.h>
+#include <linux/torture.h>
+#include <linux/vmalloc.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>");
+
+#define PERF_FLAG "-perf:"
+#define PERFOUT_STRING(s) \
+ pr_alert("%s" PERF_FLAG s "\n", perf_type)
+#define VERBOSE_PERFOUT_STRING(s) \
+ do { if (verbose) pr_alert("%s" PERF_FLAG " %s\n", perf_type, s); } while (0)
+#define VERBOSE_PERFOUT_ERRSTRING(s) \
+ do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)
+
+torture_param(bool, gp_exp, true, "Use expedited GP wait primitives");
+torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
+torture_param(int, nreaders, -1, "Number of RCU reader threads");
+torture_param(int, nwriters, -1, "Number of RCU updater threads");
+torture_param(bool, shutdown, false, "Shutdown at end of performance tests.");
+torture_param(bool, verbose, true, "Enable verbose debugging printk()s");
+
+static char *perf_type = "rcu";
+module_param(perf_type, charp, 0444);
+MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, rcu_bh, ...)");
+
+static int nrealreaders;
+static int nrealwriters;
+static struct task_struct **writer_tasks;
+static struct task_struct **reader_tasks;
+static struct task_struct *shutdown_task;
+
+static u64 **writer_durations;
+static int *writer_n_durations;
+static atomic_t n_rcu_perf_reader_started;
+static atomic_t n_rcu_perf_writer_started;
+static atomic_t n_rcu_perf_writer_finished;
+static wait_queue_head_t shutdown_wq;
+static u64 t_rcu_perf_writer_started;
+static u64 t_rcu_perf_writer_finished;
+static unsigned long b_rcu_perf_writer_started;
+static unsigned long b_rcu_perf_writer_finished;
+
+static int rcu_perf_writer_state;
+#define RTWS_INIT 0
+#define RTWS_EXP_SYNC 1
+#define RTWS_SYNC 2
+#define RTWS_IDLE 2
+#define RTWS_STOPPING 3
+
+#define MAX_MEAS 10000
+#define MIN_MEAS 100
+
+#if defined(MODULE) || defined(CONFIG_RCU_PERF_TEST_RUNNABLE)
+#define RCUPERF_RUNNABLE_INIT 1
+#else
+#define RCUPERF_RUNNABLE_INIT 0
+#endif
+static int perf_runnable = RCUPERF_RUNNABLE_INIT;
+module_param(perf_runnable, int, 0444);
+MODULE_PARM_DESC(perf_runnable, "Start rcuperf at boot");
+
+/*
+ * Operations vector for selecting different types of tests.
+ */
+
+struct rcu_perf_ops {
+ int ptype;
+ void (*init)(void);
+ void (*cleanup)(void);
+ int (*readlock)(void);
+ void (*readunlock)(int idx);
+ unsigned long (*started)(void);
+ unsigned long (*completed)(void);
+ unsigned long (*exp_completed)(void);
+ void (*sync)(void);
+ void (*exp_sync)(void);
+ const char *name;
+};
+
+static struct rcu_perf_ops *cur_ops;
+
+/*
+ * Definitions for rcu perf testing.
+ */
+
+static int rcu_perf_read_lock(void) __acquires(RCU)
+{
+ rcu_read_lock();
+ return 0;
+}
+
+static void rcu_perf_read_unlock(int idx) __releases(RCU)
+{
+ rcu_read_unlock();
+}
+
+static unsigned long __maybe_unused rcu_no_completed(void)
+{
+ return 0;
+}
+
+static void rcu_sync_perf_init(void)
+{
+}
+
+static struct rcu_perf_ops rcu_ops = {
+ .ptype = RCU_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = rcu_perf_read_lock,
+ .readunlock = rcu_perf_read_unlock,
+ .started = rcu_batches_started,
+ .completed = rcu_batches_completed,
+ .exp_completed = rcu_exp_batches_completed,
+ .sync = synchronize_rcu,
+ .exp_sync = synchronize_rcu_expedited,
+ .name = "rcu"
+};
+
+/*
+ * Definitions for rcu_bh perf testing.
+ */
+
+static int rcu_bh_perf_read_lock(void) __acquires(RCU_BH)
+{
+ rcu_read_lock_bh();
+ return 0;
+}
+
+static void rcu_bh_perf_read_unlock(int idx) __releases(RCU_BH)
+{
+ rcu_read_unlock_bh();
+}
+
+static struct rcu_perf_ops rcu_bh_ops = {
+ .ptype = RCU_BH_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = rcu_bh_perf_read_lock,
+ .readunlock = rcu_bh_perf_read_unlock,
+ .started = rcu_batches_started_bh,
+ .completed = rcu_batches_completed_bh,
+ .exp_completed = rcu_exp_batches_completed_sched,
+ .sync = synchronize_rcu_bh,
+ .exp_sync = synchronize_rcu_bh_expedited,
+ .name = "rcu_bh"
+};
+
+/*
+ * Definitions for srcu perf testing.
+ */
+
+DEFINE_STATIC_SRCU(srcu_ctl_perf);
+static struct srcu_struct *srcu_ctlp = &srcu_ctl_perf;
+
+static int srcu_perf_read_lock(void) __acquires(srcu_ctlp)
+{
+ return srcu_read_lock(srcu_ctlp);
+}
+
+static void srcu_perf_read_unlock(int idx) __releases(srcu_ctlp)
+{
+ srcu_read_unlock(srcu_ctlp, idx);
+}
+
+static unsigned long srcu_perf_completed(void)
+{
+ return srcu_batches_completed(srcu_ctlp);
+}
+
+static void srcu_perf_synchronize(void)
+{
+ synchronize_srcu(srcu_ctlp);
+}
+
+static void srcu_perf_synchronize_expedited(void)
+{
+ synchronize_srcu_expedited(srcu_ctlp);
+}
+
+static struct rcu_perf_ops srcu_ops = {
+ .ptype = SRCU_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = srcu_perf_read_lock,
+ .readunlock = srcu_perf_read_unlock,
+ .started = NULL,
+ .completed = srcu_perf_completed,
+ .exp_completed = srcu_perf_completed,
+ .sync = srcu_perf_synchronize,
+ .exp_sync = srcu_perf_synchronize_expedited,
+ .name = "srcu"
+};
+
+/*
+ * Definitions for sched perf testing.
+ */
+
+static int sched_perf_read_lock(void)
+{
+ preempt_disable();
+ return 0;
+}
+
+static void sched_perf_read_unlock(int idx)
+{
+ preempt_enable();
+}
+
+static struct rcu_perf_ops sched_ops = {
+ .ptype = RCU_SCHED_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = sched_perf_read_lock,
+ .readunlock = sched_perf_read_unlock,
+ .started = rcu_batches_started_sched,
+ .completed = rcu_batches_completed_sched,
+ .exp_completed = rcu_exp_batches_completed_sched,
+ .sync = synchronize_sched,
+ .exp_sync = synchronize_sched_expedited,
+ .name = "sched"
+};
+
+#ifdef CONFIG_TASKS_RCU
+
+/*
+ * Definitions for RCU-tasks perf testing.
+ */
+
+static int tasks_perf_read_lock(void)
+{
+ return 0;
+}
+
+static void tasks_perf_read_unlock(int idx)
+{
+}
+
+static struct rcu_perf_ops tasks_ops = {
+ .ptype = RCU_TASKS_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = tasks_perf_read_lock,
+ .readunlock = tasks_perf_read_unlock,
+ .started = rcu_no_completed,
+ .completed = rcu_no_completed,
+ .sync = synchronize_rcu_tasks,
+ .exp_sync = synchronize_rcu_tasks,
+ .name = "tasks"
+};
+
+#define RCUPERF_TASKS_OPS &tasks_ops,
+
+static bool __maybe_unused torturing_tasks(void)
+{
+ return cur_ops == &tasks_ops;
+}
+
+#else /* #ifdef CONFIG_TASKS_RCU */
+
+#define RCUPERF_TASKS_OPS
+
+static bool __maybe_unused torturing_tasks(void)
+{
+ return false;
+}
+
+#endif /* #else #ifdef CONFIG_TASKS_RCU */
+
+/*
+ * If performance tests complete, wait for shutdown to commence.
+ */
+static void rcu_perf_wait_shutdown(void)
+{
+ cond_resched_rcu_qs();
+ if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters)
+ return;
+ while (!torture_must_stop())
+ schedule_timeout_uninterruptible(1);
+}
+
+/*
+ * RCU perf reader kthread. Repeatedly does empty RCU read-side
+ * critical section, minimizing update-side interference.
+ */
+static int
+rcu_perf_reader(void *arg)
+{
+ unsigned long flags;
+ int idx;
+ long me = (long)arg;
+
+ VERBOSE_PERFOUT_STRING("rcu_perf_reader task started");
+ set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
+ set_user_nice(current, MAX_NICE);
+ atomic_inc(&n_rcu_perf_reader_started);
+
+ do {
+ local_irq_save(flags);
+ idx = cur_ops->readlock();
+ cur_ops->readunlock(idx);
+ local_irq_restore(flags);
+ rcu_perf_wait_shutdown();
+ } while (!torture_must_stop());
+ torture_kthread_stopping("rcu_perf_reader");
+ return 0;
+}
+
+/*
+ * RCU perf writer kthread. Repeatedly does a grace period.
+ */
+static int
+rcu_perf_writer(void *arg)
+{
+ int i = 0;
+ int i_max;
+ long me = (long)arg;
+ struct sched_param sp;
+ bool started = false, done = false, alldone = false;
+ u64 t;
+ u64 *wdp;
+ u64 *wdpp = writer_durations[me];
+
+ VERBOSE_PERFOUT_STRING("rcu_perf_writer task started");
+ WARN_ON(rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp);
+ WARN_ON(rcu_gp_is_normal() && gp_exp);
+ WARN_ON(!wdpp);
+ set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
+ sp.sched_priority = 1;
+ sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
+
+ if (holdoff)
+ schedule_timeout_uninterruptible(holdoff * HZ);
+
+ t = ktime_get_mono_fast_ns();
+ if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) {
+ t_rcu_perf_writer_started = t;
+ if (gp_exp) {
+ b_rcu_perf_writer_started =
+ cur_ops->exp_completed() / 2;
+ } else {
+ b_rcu_perf_writer_started =
+ cur_ops->completed();
+ }
+ }
+
+ do {
+ wdp = &wdpp[i];
+ *wdp = ktime_get_mono_fast_ns();
+ if (gp_exp) {
+ rcu_perf_writer_state = RTWS_EXP_SYNC;
+ cur_ops->exp_sync();
+ } else {
+ rcu_perf_writer_state = RTWS_SYNC;
+ cur_ops->sync();
+ }
+ rcu_perf_writer_state = RTWS_IDLE;
+ t = ktime_get_mono_fast_ns();
+ *wdp = t - *wdp;
+ i_max = i;
+ if (!started &&
+ atomic_read(&n_rcu_perf_writer_started) >= nrealwriters)
+ started = true;
+ if (!done && i >= MIN_MEAS) {
+ done = true;
+ sp.sched_priority = 0;
+ sched_setscheduler_nocheck(current,
+ SCHED_NORMAL, &sp);
+ pr_alert("%s" PERF_FLAG
+ "rcu_perf_writer %ld has %d measurements\n",
+ perf_type, me, MIN_MEAS);
+ if (atomic_inc_return(&n_rcu_perf_writer_finished) >=
+ nrealwriters) {
+ schedule_timeout_interruptible(10);
+ rcu_ftrace_dump(DUMP_ALL);
+ PERFOUT_STRING("Test complete");
+ t_rcu_perf_writer_finished = t;
+ if (gp_exp) {
+ b_rcu_perf_writer_finished =
+ cur_ops->exp_completed() / 2;
+ } else {
+ b_rcu_perf_writer_finished =
+ cur_ops->completed();
+ }
+ if (shutdown) {
+ smp_mb(); /* Assign before wake. */
+ wake_up(&shutdown_wq);
+ }
+ }
+ }
+ if (done && !alldone &&
+ atomic_read(&n_rcu_perf_writer_finished) >= nrealwriters)
+ alldone = true;
+ if (started && !alldone && i < MAX_MEAS - 1)
+ i++;
+ rcu_perf_wait_shutdown();
+ } while (!torture_must_stop());
+ rcu_perf_writer_state = RTWS_STOPPING;
+ writer_n_durations[me] = i_max;
+ torture_kthread_stopping("rcu_perf_writer");
+ return 0;
+}
+
+static inline void
+rcu_perf_print_module_parms(struct rcu_perf_ops *cur_ops, const char *tag)
+{
+ pr_alert("%s" PERF_FLAG
+ "--- %s: nreaders=%d nwriters=%d verbose=%d shutdown=%d\n",
+ perf_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
+}
+
+static void
+rcu_perf_cleanup(void)
+{
+ int i;
+ int j;
+ int ngps = 0;
+ u64 *wdp;
+ u64 *wdpp;
+
+ if (torture_cleanup_begin())
+ return;
+
+ if (reader_tasks) {
+ for (i = 0; i < nrealreaders; i++)
+ torture_stop_kthread(rcu_perf_reader,
+ reader_tasks[i]);
+ kfree(reader_tasks);
+ }
+
+ if (writer_tasks) {
+ for (i = 0; i < nrealwriters; i++) {
+ torture_stop_kthread(rcu_perf_writer,
+ writer_tasks[i]);
+ if (!writer_n_durations)
+ continue;
+ j = writer_n_durations[i];
+ pr_alert("%s%s writer %d gps: %d\n",
+ perf_type, PERF_FLAG, i, j);
+ ngps += j;
+ }
+ pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n",
+ perf_type, PERF_FLAG,
+ t_rcu_perf_writer_started, t_rcu_perf_writer_finished,
+ t_rcu_perf_writer_finished -
+ t_rcu_perf_writer_started,
+ ngps,
+ b_rcu_perf_writer_finished -
+ b_rcu_perf_writer_started);
+ for (i = 0; i < nrealwriters; i++) {
+ if (!writer_durations)
+ break;
+ if (!writer_n_durations)
+ continue;
+ wdpp = writer_durations[i];
+ if (!wdpp)
+ continue;
+ for (j = 0; j <= writer_n_durations[i]; j++) {
+ wdp = &wdpp[j];
+ pr_alert("%s%s %4d writer-duration: %5d %llu\n",
+ perf_type, PERF_FLAG,
+ i, j, *wdp);
+ if (j % 100 == 0)
+ schedule_timeout_uninterruptible(1);
+ }
+ kfree(writer_durations[i]);
+ }
+ kfree(writer_tasks);
+ kfree(writer_durations);
+ kfree(writer_n_durations);
+ }
+
+ /* Do flavor-specific cleanup operations. */
+ if (cur_ops->cleanup != NULL)
+ cur_ops->cleanup();
+
+ torture_cleanup_end();
+}
+
+/*
+ * Return the number if non-negative. If -1, the number of CPUs.
+ * If less than -1, that much less than the number of CPUs, but
+ * at least one.
+ */
+static int compute_real(int n)
+{
+ int nr;
+
+ if (n >= 0) {
+ nr = n;
+ } else {
+ nr = num_online_cpus() + 1 + n;
+ if (nr <= 0)
+ nr = 1;
+ }
+ return nr;
+}
+
+/*
+ * RCU perf shutdown kthread. Just waits to be awakened, then shuts
+ * down system.
+ */
+static int
+rcu_perf_shutdown(void *arg)
+{
+ do {
+ wait_event(shutdown_wq,
+ atomic_read(&n_rcu_perf_writer_finished) >=
+ nrealwriters);
+ } while (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters);
+ smp_mb(); /* Wake before output. */
+ rcu_perf_cleanup();
+ kernel_power_off();
+ return -EINVAL;
+}
+
+static int __init
+rcu_perf_init(void)
+{
+ long i;
+ int firsterr = 0;
+ static struct rcu_perf_ops *perf_ops[] = {
+ &rcu_ops, &rcu_bh_ops, &srcu_ops, &sched_ops,
+ RCUPERF_TASKS_OPS
+ };
+
+ if (!torture_init_begin(perf_type, verbose, &perf_runnable))
+ return -EBUSY;
+
+ /* Process args and tell the world that the perf'er is on the job. */
+ for (i = 0; i < ARRAY_SIZE(perf_ops); i++) {
+ cur_ops = perf_ops[i];
+ if (strcmp(perf_type, cur_ops->name) == 0)
+ break;
+ }
+ if (i == ARRAY_SIZE(perf_ops)) {
+ pr_alert("rcu-perf: invalid perf type: \"%s\"\n",
+ perf_type);
+ pr_alert("rcu-perf types:");
+ for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
+ pr_alert(" %s", perf_ops[i]->name);
+ pr_alert("\n");
+ firsterr = -EINVAL;
+ goto unwind;
+ }
+ if (cur_ops->init)
+ cur_ops->init();
+
+ nrealwriters = compute_real(nwriters);
+ nrealreaders = compute_real(nreaders);
+ atomic_set(&n_rcu_perf_reader_started, 0);
+ atomic_set(&n_rcu_perf_writer_started, 0);
+ atomic_set(&n_rcu_perf_writer_finished, 0);
+ rcu_perf_print_module_parms(cur_ops, "Start of test");
+
+ /* Start up the kthreads. */
+
+ if (shutdown) {
+ init_waitqueue_head(&shutdown_wq);
+ firsterr = torture_create_kthread(rcu_perf_shutdown, NULL,
+ shutdown_task);
+ if (firsterr)
+ goto unwind;
+ schedule_timeout_uninterruptible(1);
+ }
+ reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ if (reader_tasks == NULL) {
+ VERBOSE_PERFOUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealreaders; i++) {
+ firsterr = torture_create_kthread(rcu_perf_reader, (void *)i,
+ reader_tasks[i]);
+ if (firsterr)
+ goto unwind;
+ }
+ while (atomic_read(&n_rcu_perf_reader_started) < nrealreaders)
+ schedule_timeout_uninterruptible(1);
+ writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations),
+ GFP_KERNEL);
+ writer_n_durations =
+ kcalloc(nrealwriters, sizeof(*writer_n_durations),
+ GFP_KERNEL);
+ if (!writer_tasks || !writer_durations || !writer_n_durations) {
+ VERBOSE_PERFOUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealwriters; i++) {
+ writer_durations[i] =
+ kcalloc(MAX_MEAS, sizeof(*writer_durations[i]),
+ GFP_KERNEL);
+ if (!writer_durations[i])
+ goto unwind;
+ firsterr = torture_create_kthread(rcu_perf_writer, (void *)i,
+ writer_tasks[i]);
+ if (firsterr)
+ goto unwind;
+ }
+ torture_init_end();
+ return 0;
+
+unwind:
+ torture_init_end();
+ rcu_perf_cleanup();
+ return firsterr;
+}
+
+module_init(rcu_perf_init);
+module_exit(rcu_perf_cleanup);
static unsigned long rcu_torture_current_version;
static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
static DEFINE_SPINLOCK(rcu_torture_lock);
-static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) = { 0 };
-static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) = { 0 };
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count);
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch);
static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
static atomic_t n_rcu_torture_alloc;
static atomic_t n_rcu_torture_alloc_fail;
static int
rcu_torture_writer(void *arg)
{
- bool can_expedite = !rcu_gp_is_expedited();
+ bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
int expediting = 0;
unsigned long gp_snap;
bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
if (!can_expedite) {
pr_alert("%s" TORTURE_FLAG
- " Grace periods expedited from boot/sysfs for %s,\n",
+ " GP expediting controlled from boot/sysfs for %s,\n",
torture_type, cur_ops->name);
pr_alert("%s" TORTURE_FLAG
" Disabled dynamic grace-period expediting.\n",
return 0;
}
-static void rcutorture_trace_dump(void)
-{
- static atomic_t beenhere = ATOMIC_INIT(0);
-
- if (atomic_read(&beenhere))
- return;
- if (atomic_xchg(&beenhere, 1) != 0)
- return;
- ftrace_dump(DUMP_ALL);
-}
-
/*
* RCU torture reader from timer handler. Dereferences rcu_torture_current,
* incrementing the corresponding element of the pipeline array. The
if (pipe_count > 1) {
do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts,
started, completed);
- rcutorture_trace_dump();
+ rcu_ftrace_dump(DUMP_ALL);
}
__this_cpu_inc(rcu_torture_count[pipe_count]);
completed = completed - started;
if (pipe_count > 1) {
do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
ts, started, completed);
- rcutorture_trace_dump();
+ rcu_ftrace_dump(DUMP_ALL);
}
__this_cpu_inc(rcu_torture_count[pipe_count]);
completed = completed - started;
rcu_torture_writer_state,
gpnum, completed, flags);
show_rcu_gp_kthreads();
- rcutorture_trace_dump();
+ rcu_ftrace_dump(DUMP_ALL);
}
rtcv_snap = rcu_torture_current_version;
}
* The above smp_load_acquire() ensures barrier_phase load
* is ordered before the folloiwng ->call().
*/
+ local_irq_disable(); /* Just to test no-irq call_rcu(). */
cur_ops->call(&rcu, rcu_torture_barrier_cbf);
+ local_irq_enable();
if (atomic_dec_and_test(&barrier_cbs_count))
wake_up(&barrier_wq);
} while (!torture_must_stop());
{
long cpu = (long)hcpu;
- switch (action) {
+ switch (action & ~CPU_TASKS_FROZEN) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
(void)rcutorture_booster_init(cpu);
.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
.name = RCU_STATE_NAME(sname), \
.abbr = sabbr, \
+ .exp_mutex = __MUTEX_INITIALIZER(sname##_state.exp_mutex), \
+ .exp_wake_mutex = __MUTEX_INITIALIZER(sname##_state.exp_wake_mutex), \
}
RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
rcu_momentary_dyntick_idle();
local_irq_restore(flags);
}
+ if (unlikely(raw_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))) {
+ /*
+ * Yes, we just checked a per-CPU variable with preemption
+ * enabled, so we might be migrated to some other CPU at
+ * this point. That is OK because in that case, the
+ * migration will supply the needed quiescent state.
+ * We might end up needlessly disabling preemption and
+ * invoking rcu_sched_qs() on the destination CPU, but
+ * the probability and cost are both quite low, so this
+ * should not be a problem in practice.
+ */
+ preempt_disable();
+ rcu_sched_qs();
+ preempt_enable();
+ }
this_cpu_inc(rcu_qs_ctr);
barrier(); /* Avoid RCU read-side critical sections leaking up. */
}
static ulong jiffies_till_first_fqs = ULONG_MAX;
static ulong jiffies_till_next_fqs = ULONG_MAX;
+static bool rcu_kick_kthreads;
module_param(jiffies_till_first_fqs, ulong, 0644);
module_param(jiffies_till_next_fqs, ulong, 0644);
+module_param(rcu_kick_kthreads, bool, 0644);
/*
* How long the grace period must be before we start recruiting
}
EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
+/*
+ * Return the number of RCU expedited batches completed thus far for
+ * debug & stats. Odd numbers mean that a batch is in progress, even
+ * numbers mean idle. The value returned will thus be roughly double
+ * the cumulative batches since boot.
+ */
+unsigned long rcu_exp_batches_completed(void)
+{
+ return rcu_state_p->expedited_sequence;
+}
+EXPORT_SYMBOL_GPL(rcu_exp_batches_completed);
+
+/*
+ * Return the number of RCU-sched expedited batches completed thus far
+ * for debug & stats. Similar to rcu_exp_batches_completed().
+ */
+unsigned long rcu_exp_batches_completed_sched(void)
+{
+ return rcu_sched_state.expedited_sequence;
+}
+EXPORT_SYMBOL_GPL(rcu_exp_batches_completed_sched);
+
/*
* Force a quiescent state.
*/
idle_task(smp_processor_id());
trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0);
- ftrace_dump(DUMP_ORIG);
+ rcu_ftrace_dump(DUMP_ORIG);
WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
trace_rcu_dyntick(TPS("Error on exit: not idle task"),
oldval, rdtp->dynticks_nesting);
- ftrace_dump(DUMP_ORIG);
+ rcu_ftrace_dump(DUMP_ORIG);
WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
rsp->gp_flags,
gp_state_getname(rsp->gp_state), rsp->gp_state,
rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
- if (rsp->gp_kthread)
+ if (rsp->gp_kthread) {
sched_show_task(rsp->gp_kthread);
+ wake_up_process(rsp->gp_kthread);
+ }
}
}
}
}
+/*
+ * If too much time has passed in the current grace period, and if
+ * so configured, go kick the relevant kthreads.
+ */
+static void rcu_stall_kick_kthreads(struct rcu_state *rsp)
+{
+ unsigned long j;
+
+ if (!rcu_kick_kthreads)
+ return;
+ j = READ_ONCE(rsp->jiffies_kick_kthreads);
+ if (time_after(jiffies, j) && rsp->gp_kthread) {
+ WARN_ONCE(1, "Kicking %s grace-period kthread\n", rsp->name);
+ rcu_ftrace_dump(DUMP_ALL);
+ wake_up_process(rsp->gp_kthread);
+ WRITE_ONCE(rsp->jiffies_kick_kthreads, j + HZ);
+ }
+}
+
static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
{
int cpu;
struct rcu_node *rnp = rcu_get_root(rsp);
long totqlen = 0;
+ /* Kick and suppress, if so configured. */
+ rcu_stall_kick_kthreads(rsp);
+ if (rcu_cpu_stall_suppress)
+ return;
+
/* Only let one CPU complain about others per time interval. */
raw_spin_lock_irqsave_rcu_node(rnp, flags);
struct rcu_node *rnp = rcu_get_root(rsp);
long totqlen = 0;
+ /* Kick and suppress, if so configured. */
+ rcu_stall_kick_kthreads(rsp);
+ if (rcu_cpu_stall_suppress)
+ return;
+
/*
* OK, time to rat on ourselves...
* See Documentation/RCU/stallwarn.txt for info on how to debug
unsigned long js;
struct rcu_node *rnp;
- if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp))
+ if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) ||
+ !rcu_gp_in_progress(rsp))
return;
+ rcu_stall_kick_kthreads(rsp);
j = jiffies;
/*
}
ret = 0;
for (;;) {
- if (!ret)
+ if (!ret) {
rsp->jiffies_force_qs = jiffies + j;
+ WRITE_ONCE(rsp->jiffies_kick_kthreads,
+ jiffies + 3 * j);
+ }
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gpnum),
TPS("fqswait"));
TPS("fqsend"));
cond_resched_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
+ ret = 0; /* Force full wait till next FQS. */
+ j = jiffies_till_next_fqs;
+ if (j > HZ) {
+ j = HZ;
+ jiffies_till_next_fqs = HZ;
+ } else if (j < 1) {
+ j = 1;
+ jiffies_till_next_fqs = 1;
+ }
} else {
/* Deal with stray signal. */
cond_resched_rcu_qs();
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gpnum),
TPS("fqswaitsig"));
- }
- j = jiffies_till_next_fqs;
- if (j > HZ) {
- j = HZ;
- jiffies_till_next_fqs = HZ;
- } else if (j < 1) {
- j = 1;
- jiffies_till_next_fqs = 1;
+ ret = 1; /* Keep old FQS timing. */
+ j = jiffies;
+ if (time_after(jiffies, rsp->jiffies_force_qs))
+ j = 1;
+ else
+ j = rsp->jiffies_force_qs - j;
}
}
}
static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
{
+ unsigned long s;
+
smp_mb(); /* Caller's modifications seen first by other CPUs. */
- return rcu_seq_snap(&rsp->expedited_sequence);
+ s = rcu_seq_snap(&rsp->expedited_sequence);
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("snap"));
+ return s;
}
static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
{
* for the current expedited grace period. Works only for preemptible
* RCU -- other RCU implementation use other means.
*
- * Caller must hold the root rcu_node's exp_funnel_mutex.
+ * Caller must hold the rcu_state's exp_mutex.
*/
static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
{
* recursively up the tree. (Calm down, calm down, we do the recursion
* iteratively!)
*
- * Caller must hold the root rcu_node's exp_funnel_mutex and the
- * specified rcu_node structure's ->lock.
+ * Caller must hold the rcu_state's exp_mutex and the specified rcu_node
+ * structure's ->lock.
*/
static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake, unsigned long flags)
* Report expedited quiescent state for specified node. This is a
* lock-acquisition wrapper function for __rcu_report_exp_rnp().
*
- * Caller must hold the root rcu_node's exp_funnel_mutex.
+ * Caller must hold the rcu_state's exp_mutex.
*/
static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
struct rcu_node *rnp, bool wake)
/*
* Report expedited quiescent state for multiple CPUs, all covered by the
- * specified leaf rcu_node structure. Caller must hold the root
- * rcu_node's exp_funnel_mutex.
+ * specified leaf rcu_node structure. Caller must hold the rcu_state's
+ * exp_mutex.
*/
static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
unsigned long mask, bool wake)
/*
* Report expedited quiescent state for specified rcu_data (CPU).
- * Caller must hold the root rcu_node's exp_funnel_mutex.
*/
static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp,
bool wake)
}
/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */
-static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp,
- struct rcu_data *rdp,
- atomic_long_t *stat, unsigned long s)
+static bool sync_exp_work_done(struct rcu_state *rsp, atomic_long_t *stat,
+ unsigned long s)
{
if (rcu_exp_gp_seq_done(rsp, s)) {
- if (rnp)
- mutex_unlock(&rnp->exp_funnel_mutex);
- else if (rdp)
- mutex_unlock(&rdp->exp_funnel_mutex);
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("done"));
/* Ensure test happens before caller kfree(). */
smp_mb__before_atomic(); /* ^^^ */
atomic_long_inc(stat);
}
/*
- * Funnel-lock acquisition for expedited grace periods. Returns a
- * pointer to the root rcu_node structure, or NULL if some other
- * task did the expedited grace period for us.
+ * Funnel-lock acquisition for expedited grace periods. Returns true
+ * if some other task completed an expedited grace period that this task
+ * can piggy-back on, and with no mutex held. Otherwise, returns false
+ * with the mutex held, indicating that the caller must actually do the
+ * expedited grace period.
*/
-static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
+static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
{
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id());
- struct rcu_node *rnp0;
- struct rcu_node *rnp1 = NULL;
+ struct rcu_node *rnp = rdp->mynode;
+ struct rcu_node *rnp_root = rcu_get_root(rsp);
+
+ /* Low-contention fastpath. */
+ if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) &&
+ (rnp == rnp_root ||
+ ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) &&
+ !mutex_is_locked(&rsp->exp_mutex) &&
+ mutex_trylock(&rsp->exp_mutex))
+ goto fastpath;
/*
- * First try directly acquiring the root lock in order to reduce
- * latency in the common case where expedited grace periods are
- * rare. We check mutex_is_locked() to avoid pathological levels of
- * memory contention on ->exp_funnel_mutex in the heavy-load case.
+ * Each pass through the following loop works its way up
+ * the rcu_node tree, returning if others have done the work or
+ * otherwise falls through to acquire rsp->exp_mutex. The mapping
+ * from CPU to rcu_node structure can be inexact, as it is just
+ * promoting locality and is not strictly needed for correctness.
*/
- rnp0 = rcu_get_root(rsp);
- if (!mutex_is_locked(&rnp0->exp_funnel_mutex)) {
- if (mutex_trylock(&rnp0->exp_funnel_mutex)) {
- if (sync_exp_work_done(rsp, rnp0, NULL,
- &rdp->expedited_workdone0, s))
- return NULL;
- return rnp0;
+ for (; rnp != NULL; rnp = rnp->parent) {
+ if (sync_exp_work_done(rsp, &rdp->exp_workdone1, s))
+ return true;
+
+ /* Work not done, either wait here or go up. */
+ spin_lock(&rnp->exp_lock);
+ if (ULONG_CMP_GE(rnp->exp_seq_rq, s)) {
+
+ /* Someone else doing GP, so wait for them. */
+ spin_unlock(&rnp->exp_lock);
+ trace_rcu_exp_funnel_lock(rsp->name, rnp->level,
+ rnp->grplo, rnp->grphi,
+ TPS("wait"));
+ wait_event(rnp->exp_wq[(s >> 1) & 0x3],
+ sync_exp_work_done(rsp,
+ &rdp->exp_workdone2, s));
+ return true;
}
+ rnp->exp_seq_rq = s; /* Followers can wait on us. */
+ spin_unlock(&rnp->exp_lock);
+ trace_rcu_exp_funnel_lock(rsp->name, rnp->level, rnp->grplo,
+ rnp->grphi, TPS("nxtlvl"));
}
-
- /*
- * Each pass through the following loop works its way
- * up the rcu_node tree, returning if others have done the
- * work or otherwise falls through holding the root rnp's
- * ->exp_funnel_mutex. The mapping from CPU to rcu_node structure
- * can be inexact, as it is just promoting locality and is not
- * strictly needed for correctness.
- */
- if (sync_exp_work_done(rsp, NULL, NULL, &rdp->expedited_workdone1, s))
- return NULL;
- mutex_lock(&rdp->exp_funnel_mutex);
- rnp0 = rdp->mynode;
- for (; rnp0 != NULL; rnp0 = rnp0->parent) {
- if (sync_exp_work_done(rsp, rnp1, rdp,
- &rdp->expedited_workdone2, s))
- return NULL;
- mutex_lock(&rnp0->exp_funnel_mutex);
- if (rnp1)
- mutex_unlock(&rnp1->exp_funnel_mutex);
- else
- mutex_unlock(&rdp->exp_funnel_mutex);
- rnp1 = rnp0;
+ mutex_lock(&rsp->exp_mutex);
+fastpath:
+ if (sync_exp_work_done(rsp, &rdp->exp_workdone3, s)) {
+ mutex_unlock(&rsp->exp_mutex);
+ return true;
}
- if (sync_exp_work_done(rsp, rnp1, rdp,
- &rdp->expedited_workdone3, s))
- return NULL;
- return rnp1;
+ rcu_exp_gp_seq_start(rsp);
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("start"));
+ return false;
}
/* Invoked on each online non-idle CPU for expedited quiescent state. */
if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))
return;
+ if (rcu_is_cpu_rrupt_from_idle()) {
+ rcu_report_exp_rdp(&rcu_sched_state,
+ this_cpu_ptr(&rcu_sched_data), true);
+ return;
+ }
__this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, true);
resched_cpu(smp_processor_id());
}
rsp->name);
ndetected = 0;
rcu_for_each_leaf_node(rsp, rnp) {
- ndetected = rcu_print_task_exp_stall(rnp);
+ ndetected += rcu_print_task_exp_stall(rnp);
mask = 1;
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) {
struct rcu_data *rdp;
ndetected++;
rdp = per_cpu_ptr(rsp->rda, cpu);
pr_cont(" %d-%c%c%c", cpu,
- "O."[cpu_online(cpu)],
+ "O."[!!cpu_online(cpu)],
"o."[!!(rdp->grpmask & rnp->expmaskinit)],
"N."[!!(rdp->grpmask & rnp->expmaskinitnext)]);
}
pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",
jiffies - jiffies_start, rsp->expedited_sequence,
rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]);
- if (!ndetected) {
+ if (ndetected) {
pr_err("blocking rcu_node structures:");
rcu_for_each_node_breadth_first(rsp, rnp) {
if (rnp == rnp_root)
}
}
+/*
+ * Wait for the current expedited grace period to complete, and then
+ * wake up everyone who piggybacked on the just-completed expedited
+ * grace period. Also update all the ->exp_seq_rq counters as needed
+ * in order to avoid counter-wrap problems.
+ */
+static void rcu_exp_wait_wake(struct rcu_state *rsp, unsigned long s)
+{
+ struct rcu_node *rnp;
+
+ synchronize_sched_expedited_wait(rsp);
+ rcu_exp_gp_seq_end(rsp);
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("end"));
+
+ /*
+ * Switch over to wakeup mode, allowing the next GP, but -only- the
+ * next GP, to proceed.
+ */
+ mutex_lock(&rsp->exp_wake_mutex);
+ mutex_unlock(&rsp->exp_mutex);
+
+ rcu_for_each_node_breadth_first(rsp, rnp) {
+ if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s)) {
+ spin_lock(&rnp->exp_lock);
+ /* Recheck, avoid hang in case someone just arrived. */
+ if (ULONG_CMP_LT(rnp->exp_seq_rq, s))
+ rnp->exp_seq_rq = s;
+ spin_unlock(&rnp->exp_lock);
+ }
+ wake_up_all(&rnp->exp_wq[(rsp->expedited_sequence >> 1) & 0x3]);
+ }
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("endwake"));
+ mutex_unlock(&rsp->exp_wake_mutex);
+}
+
/**
* synchronize_sched_expedited - Brute-force RCU-sched grace period
*
void synchronize_sched_expedited(void)
{
unsigned long s;
- struct rcu_node *rnp;
struct rcu_state *rsp = &rcu_sched_state;
/* If only one CPU, this is automatically a grace period. */
/* Take a snapshot of the sequence number. */
s = rcu_exp_gp_seq_snap(rsp);
-
- rnp = exp_funnel_lock(rsp, s);
- if (rnp == NULL)
+ if (exp_funnel_lock(rsp, s))
return; /* Someone else did our work for us. */
- rcu_exp_gp_seq_start(rsp);
+ /* Initialize the rcu_node tree in preparation for the wait. */
sync_rcu_exp_select_cpus(rsp, sync_sched_exp_handler);
- synchronize_sched_expedited_wait(rsp);
- rcu_exp_gp_seq_end(rsp);
- mutex_unlock(&rnp->exp_funnel_mutex);
+ /* Wait and clean up, including waking everyone. */
+ rcu_exp_wait_wake(rsp, s);
}
EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
rdp->cpu = cpu;
rdp->rsp = rsp;
- mutex_init(&rdp->exp_funnel_mutex);
rcu_boot_init_nocb_percpu_data(rdp);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
{
static const char * const buf[] = RCU_NODE_NAME_INIT;
static const char * const fqs[] = RCU_FQS_NAME_INIT;
- static const char * const exp[] = RCU_EXP_NAME_INIT;
static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
- static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS];
static u8 fl_mask = 0x1;
int levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */
rnp->level = i;
INIT_LIST_HEAD(&rnp->blkd_tasks);
rcu_init_one_nocb(rnp);
- mutex_init(&rnp->exp_funnel_mutex);
- lockdep_set_class_and_name(&rnp->exp_funnel_mutex,
- &rcu_exp_class[i], exp[i]);
+ init_waitqueue_head(&rnp->exp_wq[0]);
+ init_waitqueue_head(&rnp->exp_wq[1]);
+ init_waitqueue_head(&rnp->exp_wq[2]);
+ init_waitqueue_head(&rnp->exp_wq[3]);
+ spin_lock_init(&rnp->exp_lock);
}
}
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 }
# define RCU_NODE_NAME_INIT { "rcu_node_0" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" }
-# define RCU_EXP_NAME_INIT { "rcu_node_exp_0" }
#elif NR_CPUS <= RCU_FANOUT_2
# define RCU_NUM_LVLS 2
# define NUM_RCU_LVL_0 1
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 }
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" }
-# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1" }
#elif NR_CPUS <= RCU_FANOUT_3
# define RCU_NUM_LVLS 3
# define NUM_RCU_LVL_0 1
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 }
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" }
-# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2" }
#elif NR_CPUS <= RCU_FANOUT_4
# define RCU_NUM_LVLS 4
# define NUM_RCU_LVL_0 1
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 }
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" }
-# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2", "rcu_node_exp_3" }
#else
# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */
/* Counts of upcoming no-CB GP requests. */
raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
- struct mutex exp_funnel_mutex ____cacheline_internodealigned_in_smp;
+ spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
+ unsigned long exp_seq_rq;
+ wait_queue_head_t exp_wq[4];
} ____cacheline_internodealigned_in_smp;
/*
#ifdef CONFIG_RCU_FAST_NO_HZ
struct rcu_head oom_head;
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
- struct mutex exp_funnel_mutex;
- atomic_long_t expedited_workdone0; /* # done by others #0. */
- atomic_long_t expedited_workdone1; /* # done by others #1. */
- atomic_long_t expedited_workdone2; /* # done by others #2. */
- atomic_long_t expedited_workdone3; /* # done by others #3. */
+ atomic_long_t exp_workdone1; /* # done by others #1. */
+ atomic_long_t exp_workdone2; /* # done by others #2. */
+ atomic_long_t exp_workdone3; /* # done by others #3. */
/* 7) Callback offloading. */
#ifdef CONFIG_RCU_NOCB_CPU
/* _rcu_barrier(). */
/* End of fields guarded by barrier_mutex. */
+ struct mutex exp_mutex; /* Serialize expedited GP. */
+ struct mutex exp_wake_mutex; /* Serialize wakeup. */
unsigned long expedited_sequence; /* Take a ticket. */
atomic_long_t expedited_normal; /* # fallbacks to normal. */
atomic_t expedited_need_qs; /* # CPUs left to check in. */
unsigned long jiffies_force_qs; /* Time at which to invoke */
/* force_quiescent_state(). */
+ unsigned long jiffies_kick_kthreads; /* Time at which to kick */
+ /* kthreads, if configured. */
unsigned long n_force_qs; /* Number of calls to */
/* force_quiescent_state(). */
unsigned long n_force_qs_lh; /* ~Number of calls leaving */
* synchronize_rcu_expedited - Brute-force RCU grace period
*
* Wait for an RCU-preempt grace period, but expedite it. The basic
- * idea is to invoke synchronize_sched_expedited() to push all the tasks to
- * the ->blkd_tasks lists and wait for this list to drain. This consumes
- * significant time on all CPUs and is unfriendly to real-time workloads,
- * so is thus not recommended for any sort of common-case code.
- * In fact, if you are using synchronize_rcu_expedited() in a loop,
- * please restructure your code to batch your updates, and then Use a
- * single synchronize_rcu() instead.
+ * idea is to IPI all non-idle non-nohz online CPUs. The IPI handler
+ * checks whether the CPU is in an RCU-preempt critical section, and
+ * if so, it sets a flag that causes the outermost rcu_read_unlock()
+ * to report the quiescent state. On the other hand, if the CPU is
+ * not in an RCU read-side critical section, the IPI handler reports
+ * the quiescent state immediately.
+ *
+ * Although this is a greate improvement over previous expedited
+ * implementations, it is still unfriendly to real-time workloads, so is
+ * thus not recommended for any sort of common-case code. In fact, if
+ * you are using synchronize_rcu_expedited() in a loop, please restructure
+ * your code to batch your updates, and then Use a single synchronize_rcu()
+ * instead.
*/
void synchronize_rcu_expedited(void)
{
- struct rcu_node *rnp;
- struct rcu_node *rnp_unlock;
struct rcu_state *rsp = rcu_state_p;
unsigned long s;
}
s = rcu_exp_gp_seq_snap(rsp);
-
- rnp_unlock = exp_funnel_lock(rsp, s);
- if (rnp_unlock == NULL)
+ if (exp_funnel_lock(rsp, s))
return; /* Someone else did our work for us. */
- rcu_exp_gp_seq_start(rsp);
-
/* Initialize the rcu_node tree in preparation for the wait. */
sync_rcu_exp_select_cpus(rsp, sync_rcu_exp_handler);
- /* Wait for snapshotted ->blkd_tasks lists to drain. */
- rnp = rcu_get_root(rsp);
- synchronize_sched_expedited_wait(rsp);
-
- /* Clean up and exit. */
- rcu_exp_gp_seq_end(rsp);
- mutex_unlock(&rnp_unlock->exp_funnel_mutex);
+ /* Wait for ->blkd_tasks lists to drain, then wake everyone up. */
+ rcu_exp_wait_wake(rsp, s);
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
int cpu;
struct rcu_state *rsp = (struct rcu_state *)m->private;
struct rcu_data *rdp;
- unsigned long s0 = 0, s1 = 0, s2 = 0, s3 = 0;
+ unsigned long s1 = 0, s2 = 0, s3 = 0;
for_each_possible_cpu(cpu) {
rdp = per_cpu_ptr(rsp->rda, cpu);
- s0 += atomic_long_read(&rdp->expedited_workdone0);
- s1 += atomic_long_read(&rdp->expedited_workdone1);
- s2 += atomic_long_read(&rdp->expedited_workdone2);
- s3 += atomic_long_read(&rdp->expedited_workdone3);
+ s1 += atomic_long_read(&rdp->exp_workdone1);
+ s2 += atomic_long_read(&rdp->exp_workdone2);
+ s3 += atomic_long_read(&rdp->exp_workdone3);
}
- seq_printf(m, "s=%lu wd0=%lu wd1=%lu wd2=%lu wd3=%lu n=%lu enq=%d sc=%lu\n",
- rsp->expedited_sequence, s0, s1, s2, s3,
+ seq_printf(m, "s=%lu wd1=%lu wd2=%lu wd3=%lu n=%lu enq=%d sc=%lu\n",
+ rsp->expedited_sequence, s1, s2, s3,
atomic_long_read(&rsp->expedited_normal),
atomic_read(&rsp->expedited_need_qs),
rsp->expedited_sequence / 2);
module_param(rcu_normal_after_boot, int, 0);
#endif /* #ifndef CONFIG_TINY_RCU */
-#if defined(CONFIG_DEBUG_LOCK_ALLOC) && defined(CONFIG_PREEMPT_COUNT)
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
/**
* rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
*
return 0;
if (debug_locks)
lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
- return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
+ return lockdep_opinion || !preemptible();
}
EXPORT_SYMBOL(rcu_read_lock_sched_held);
#endif
!cpumask_test_cpu(later_rq->cpu,
&task->cpus_allowed) ||
task_running(rq, task) ||
+ !dl_task(task) ||
!task_on_rq_queued(task))) {
double_unlock_balance(rq, later_rq);
later_rq = NULL;
#else /* CONFIG_SMP */
-static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
+static inline void update_load_avg(struct sched_entity *se, int not_used)
+{
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ struct rq *rq = rq_of(cfs_rq);
+
+ cpufreq_trigger_update(rq_clock(rq));
+}
+
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
static void
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
- bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING);
- bool curr = cfs_rq->curr == se;
-
/*
- * If we're the current task, we must renormalise before calling
- * update_curr().
+ * Update the normalized vruntime before updating min_vruntime
+ * through calling update_curr().
*/
- if (renorm && curr)
+ if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
se->vruntime += cfs_rq->min_vruntime;
- update_curr(cfs_rq);
-
/*
- * Otherwise, renormalise after, such that we're placed at the current
- * moment in time, instead of some random moment in the past.
+ * Update run-time statistics of the 'current'.
*/
- if (renorm && !curr)
- se->vruntime += cfs_rq->min_vruntime;
-
+ update_curr(cfs_rq);
enqueue_entity_load_avg(cfs_rq, se);
account_entity_enqueue(cfs_rq, se);
update_cfs_shares(cfs_rq);
update_stats_enqueue(cfs_rq, se);
check_spread(cfs_rq, se);
}
- if (!curr)
+ if (se != cfs_rq->curr)
__enqueue_entity(cfs_rq, se);
se->on_rq = 1;
!cpumask_test_cpu(lowest_rq->cpu,
tsk_cpus_allowed(task)) ||
task_running(rq, task) ||
+ !rt_task(task) ||
!task_on_rq_queued(task))) {
double_unlock_balance(rq, lowest_rq);
oss.ss_sp = (void __user *) current->sas_ss_sp;
oss.ss_size = current->sas_ss_size;
- oss.ss_flags = sas_ss_flags(sp);
+ oss.ss_flags = sas_ss_flags(sp) |
+ (current->sas_ss_flags & SS_FLAG_BITS);
if (uss) {
void __user *ss_sp;
size_t ss_size;
- int ss_flags;
+ unsigned ss_flags;
+ int ss_mode;
error = -EFAULT;
if (!access_ok(VERIFY_READ, uss, sizeof(*uss)))
if (on_sig_stack(sp))
goto out;
+ ss_mode = ss_flags & ~SS_FLAG_BITS;
error = -EINVAL;
- /*
- * Note - this code used to test ss_flags incorrectly:
- * old code may have been written using ss_flags==0
- * to mean ss_flags==SS_ONSTACK (as this was the only
- * way that worked) - this fix preserves that older
- * mechanism.
- */
- if (ss_flags != SS_DISABLE && ss_flags != SS_ONSTACK && ss_flags != 0)
+ if (ss_mode != SS_DISABLE && ss_mode != SS_ONSTACK &&
+ ss_mode != 0)
goto out;
- if (ss_flags == SS_DISABLE) {
+ if (ss_mode == SS_DISABLE) {
ss_size = 0;
ss_sp = NULL;
} else {
current->sas_ss_sp = (unsigned long) ss_sp;
current->sas_ss_size = ss_size;
+ current->sas_ss_flags = ss_flags;
}
error = 0;
int __save_altstack(stack_t __user *uss, unsigned long sp)
{
struct task_struct *t = current;
- return __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) |
- __put_user(sas_ss_flags(sp), &uss->ss_flags) |
+ int err = __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) |
+ __put_user(t->sas_ss_flags, &uss->ss_flags) |
__put_user(t->sas_ss_size, &uss->ss_size);
+ if (err)
+ return err;
+ if (t->sas_ss_flags & SS_AUTODISARM)
+ sas_ss_reset(t);
+ return 0;
}
#ifdef CONFIG_COMPAT
torture_shutdown_hook();
else
VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
+ ftrace_dump(DUMP_ALL);
kernel_power_off(); /* Shut down the system. */
return 0;
}
{
mutex_lock(&fullstop_mutex);
if (torture_type != NULL) {
- pr_alert("torture_init_begin: refusing %s init: %s running",
+ pr_alert("torture_init_begin: Refusing %s init: %s running.\n",
ttype, torture_type);
+ pr_alert("torture_init_begin: One torture test at a time!\n");
mutex_unlock(&fullstop_mutex);
return false;
}
pool->attrs->cpumask) < 0);
spin_lock_irq(&pool->lock);
+
+ /*
+ * XXX: CPU hotplug notifiers are weird and can call DOWN_FAILED
+ * w/o preceding DOWN_PREPARE. Work around it. CPU hotplug is
+ * being reworked and this can go away in time.
+ */
+ if (!(pool->flags & POOL_DISASSOCIATED)) {
+ spin_unlock_irq(&pool->lock);
+ return;
+ }
+
pool->flags &= ~POOL_DISASSOCIATED;
for_each_pool_worker(worker, pool) {
tristate
default n
+config RCU_PERF_TEST
+ tristate "performance tests for RCU"
+ depends on DEBUG_KERNEL
+ select TORTURE_TEST
+ select SRCU
+ select TASKS_RCU
+ default n
+ help
+ This option provides a kernel module that runs performance
+ tests on the RCU infrastructure. The kernel module may be built
+ after the fact on the running kernel to be tested, if desired.
+
+ Say Y here if you want RCU performance tests to be built into
+ the kernel.
+ Say M if you want the RCU performance tests to build as a module.
+ Say N if you are unsure.
+
+config RCU_PERF_TEST_RUNNABLE
+ bool "performance tests for RCU runnable by default"
+ depends on RCU_PERF_TEST = y
+ default n
+ help
+ This option provides a way to build the RCU performance tests
+ directly into the kernel without them starting up at boot time.
+ You can use /sys/module to manually override this setting.
+ This /proc file is available only when the RCU performance
+ tests have been built into the kernel.
+
+ Say Y here if you want the RCU performance tests to start during
+ boot (you probably don't).
+ Say N here if you want the RCU performance tests to start only
+ after being manually enabled via /sys/module.
+
config RCU_TORTURE_TEST
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
rbtree.o radix-tree.o dump_stack.o timerqueue.o\
idr.o int_sqrt.o extable.o \
sha1.o md5.o irq_regs.o argv_split.o \
- proportions.o flex_proportions.o ratelimit.o show_mem.o \
+ flex_proportions.o ratelimit.o show_mem.o \
is_single_threaded.o plist.o decompress.o kobject_uevent.o \
earlycpio.o seq_buf.o nmi_backtrace.o
/* Extract a tag from the data */
tag = data[dp++];
- if (tag == 0) {
+ if (tag == ASN1_EOC) {
/* It appears to be an EOC. */
if (data[dp++] != 0)
goto invalid_eoc;
/* Extract the length */
len = data[dp++];
- if (len <= 0x7f) {
- dp += len;
- goto next_tag;
- }
+ if (len <= 0x7f)
+ goto check_length;
if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
/* Indefinite length */
}
n = len - 0x80;
- if (unlikely(n > sizeof(size_t) - 1))
+ if (unlikely(n > sizeof(len) - 1))
goto length_too_long;
if (unlikely(n > datalen - dp))
goto data_overrun_error;
- for (len = 0; n > 0; n--) {
+ len = 0;
+ for (; n > 0; n--) {
len <<= 8;
len |= data[dp++];
}
+check_length:
+ if (len > datalen - dp)
+ goto data_overrun_error;
dp += len;
goto next_tag;
}
EXPORT_SYMBOL(iov_iter_alignment);
+unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
+{
+ unsigned long res = 0;
+ size_t size = i->count;
+ if (!size)
+ return 0;
+
+ iterate_all_kinds(i, size, v,
+ (res |= (!res ? 0 : (unsigned long)v.iov_base) |
+ (size != v.iov_len ? size : 0), 0),
+ (res |= (!res ? 0 : (unsigned long)v.bv_offset) |
+ (size != v.bv_len ? size : 0)),
+ (res |= (!res ? 0 : (unsigned long)v.iov_base) |
+ (size != v.iov_len ? size : 0))
+ );
+ return res;
+}
+EXPORT_SYMBOL(iov_iter_gap_alignment);
+
ssize_t iov_iter_get_pages(struct iov_iter *i,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start)
+++ /dev/null
-/*
- * Floating proportions
- *
- * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
- *
- * Description:
- *
- * The floating proportion is a time derivative with an exponentially decaying
- * history:
- *
- * p_{j} = \Sum_{i=0} (dx_{j}/dt_{-i}) / 2^(1+i)
- *
- * Where j is an element from {prop_local}, x_{j} is j's number of events,
- * and i the time period over which the differential is taken. So d/dt_{-i} is
- * the differential over the i-th last period.
- *
- * The decaying history gives smooth transitions. The time differential carries
- * the notion of speed.
- *
- * The denominator is 2^(1+i) because we want the series to be normalised, ie.
- *
- * \Sum_{i=0} 1/2^(1+i) = 1
- *
- * Further more, if we measure time (t) in the same events as x; so that:
- *
- * t = \Sum_{j} x_{j}
- *
- * we get that:
- *
- * \Sum_{j} p_{j} = 1
- *
- * Writing this in an iterative fashion we get (dropping the 'd's):
- *
- * if (++x_{j}, ++t > period)
- * t /= 2;
- * for_each (j)
- * x_{j} /= 2;
- *
- * so that:
- *
- * p_{j} = x_{j} / t;
- *
- * We optimize away the '/= 2' for the global time delta by noting that:
- *
- * if (++t > period) t /= 2:
- *
- * Can be approximated by:
- *
- * period/2 + (++t % period/2)
- *
- * [ Furthermore, when we choose period to be 2^n it can be written in terms of
- * binary operations and wraparound artefacts disappear. ]
- *
- * Also note that this yields a natural counter of the elapsed periods:
- *
- * c = t / (period/2)
- *
- * [ Its monotonic increasing property can be applied to mitigate the wrap-
- * around issue. ]
- *
- * This allows us to do away with the loop over all prop_locals on each period
- * expiration. By remembering the period count under which it was last accessed
- * as c_{j}, we can obtain the number of 'missed' cycles from:
- *
- * c - c_{j}
- *
- * We can then lazily catch up to the global period count every time we are
- * going to use x_{j}, by doing:
- *
- * x_{j} /= 2^(c - c_{j}), c_{j} = c
- */
-
-#include <linux/proportions.h>
-#include <linux/rcupdate.h>
-
-int prop_descriptor_init(struct prop_descriptor *pd, int shift, gfp_t gfp)
-{
- int err;
-
- if (shift > PROP_MAX_SHIFT)
- shift = PROP_MAX_SHIFT;
-
- pd->index = 0;
- pd->pg[0].shift = shift;
- mutex_init(&pd->mutex);
- err = percpu_counter_init(&pd->pg[0].events, 0, gfp);
- if (err)
- goto out;
-
- err = percpu_counter_init(&pd->pg[1].events, 0, gfp);
- if (err)
- percpu_counter_destroy(&pd->pg[0].events);
-
-out:
- return err;
-}
-
-/*
- * We have two copies, and flip between them to make it seem like an atomic
- * update. The update is not really atomic wrt the events counter, but
- * it is internally consistent with the bit layout depending on shift.
- *
- * We copy the events count, move the bits around and flip the index.
- */
-void prop_change_shift(struct prop_descriptor *pd, int shift)
-{
- int index;
- int offset;
- u64 events;
- unsigned long flags;
-
- if (shift > PROP_MAX_SHIFT)
- shift = PROP_MAX_SHIFT;
-
- mutex_lock(&pd->mutex);
-
- index = pd->index ^ 1;
- offset = pd->pg[pd->index].shift - shift;
- if (!offset)
- goto out;
-
- pd->pg[index].shift = shift;
-
- local_irq_save(flags);
- events = percpu_counter_sum(&pd->pg[pd->index].events);
- if (offset < 0)
- events <<= -offset;
- else
- events >>= offset;
- percpu_counter_set(&pd->pg[index].events, events);
-
- /*
- * ensure the new pg is fully written before the switch
- */
- smp_wmb();
- pd->index = index;
- local_irq_restore(flags);
-
- synchronize_rcu();
-
-out:
- mutex_unlock(&pd->mutex);
-}
-
-/*
- * wrap the access to the data in an rcu_read_lock() section;
- * this is used to track the active references.
- */
-static struct prop_global *prop_get_global(struct prop_descriptor *pd)
-__acquires(RCU)
-{
- int index;
-
- rcu_read_lock();
- index = pd->index;
- /*
- * match the wmb from vcd_flip()
- */
- smp_rmb();
- return &pd->pg[index];
-}
-
-static void prop_put_global(struct prop_descriptor *pd, struct prop_global *pg)
-__releases(RCU)
-{
- rcu_read_unlock();
-}
-
-static void
-prop_adjust_shift(int *pl_shift, unsigned long *pl_period, int new_shift)
-{
- int offset = *pl_shift - new_shift;
-
- if (!offset)
- return;
-
- if (offset < 0)
- *pl_period <<= -offset;
- else
- *pl_period >>= offset;
-
- *pl_shift = new_shift;
-}
-
-/*
- * PERCPU
- */
-
-#define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
-
-int prop_local_init_percpu(struct prop_local_percpu *pl, gfp_t gfp)
-{
- raw_spin_lock_init(&pl->lock);
- pl->shift = 0;
- pl->period = 0;
- return percpu_counter_init(&pl->events, 0, gfp);
-}
-
-void prop_local_destroy_percpu(struct prop_local_percpu *pl)
-{
- percpu_counter_destroy(&pl->events);
-}
-
-/*
- * Catch up with missed period expirations.
- *
- * until (c_{j} == c)
- * x_{j} -= x_{j}/2;
- * c_{j}++;
- */
-static
-void prop_norm_percpu(struct prop_global *pg, struct prop_local_percpu *pl)
-{
- unsigned long period = 1UL << (pg->shift - 1);
- unsigned long period_mask = ~(period - 1);
- unsigned long global_period;
- unsigned long flags;
-
- global_period = percpu_counter_read(&pg->events);
- global_period &= period_mask;
-
- /*
- * Fast path - check if the local and global period count still match
- * outside of the lock.
- */
- if (pl->period == global_period)
- return;
-
- raw_spin_lock_irqsave(&pl->lock, flags);
- prop_adjust_shift(&pl->shift, &pl->period, pg->shift);
-
- /*
- * For each missed period, we half the local counter.
- * basically:
- * pl->events >> (global_period - pl->period);
- */
- period = (global_period - pl->period) >> (pg->shift - 1);
- if (period < BITS_PER_LONG) {
- s64 val = percpu_counter_read(&pl->events);
-
- if (val < (nr_cpu_ids * PROP_BATCH))
- val = percpu_counter_sum(&pl->events);
-
- __percpu_counter_add(&pl->events, -val + (val >> period),
- PROP_BATCH);
- } else
- percpu_counter_set(&pl->events, 0);
-
- pl->period = global_period;
- raw_spin_unlock_irqrestore(&pl->lock, flags);
-}
-
-/*
- * ++x_{j}, ++t
- */
-void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
-{
- struct prop_global *pg = prop_get_global(pd);
-
- prop_norm_percpu(pg, pl);
- __percpu_counter_add(&pl->events, 1, PROP_BATCH);
- percpu_counter_add(&pg->events, 1);
- prop_put_global(pd, pg);
-}
-
-/*
- * identical to __prop_inc_percpu, except that it limits this pl's fraction to
- * @frac/PROP_FRAC_BASE by ignoring events when this limit has been exceeded.
- */
-void __prop_inc_percpu_max(struct prop_descriptor *pd,
- struct prop_local_percpu *pl, long frac)
-{
- struct prop_global *pg = prop_get_global(pd);
-
- prop_norm_percpu(pg, pl);
-
- if (unlikely(frac != PROP_FRAC_BASE)) {
- unsigned long period_2 = 1UL << (pg->shift - 1);
- unsigned long counter_mask = period_2 - 1;
- unsigned long global_count;
- long numerator, denominator;
-
- numerator = percpu_counter_read_positive(&pl->events);
- global_count = percpu_counter_read(&pg->events);
- denominator = period_2 + (global_count & counter_mask);
-
- if (numerator > ((denominator * frac) >> PROP_FRAC_SHIFT))
- goto out_put;
- }
-
- percpu_counter_add(&pl->events, 1);
- percpu_counter_add(&pg->events, 1);
-
-out_put:
- prop_put_global(pd, pg);
-}
-
-/*
- * Obtain a fraction of this proportion
- *
- * p_{j} = x_{j} / (period/2 + t % period/2)
- */
-void prop_fraction_percpu(struct prop_descriptor *pd,
- struct prop_local_percpu *pl,
- long *numerator, long *denominator)
-{
- struct prop_global *pg = prop_get_global(pd);
- unsigned long period_2 = 1UL << (pg->shift - 1);
- unsigned long counter_mask = period_2 - 1;
- unsigned long global_count;
-
- prop_norm_percpu(pg, pl);
- *numerator = percpu_counter_read_positive(&pl->events);
-
- global_count = percpu_counter_read(&pg->events);
- *denominator = period_2 + (global_count & counter_mask);
-
- prop_put_global(pd, pg);
-}
-
-/*
- * SINGLE
- */
-
-int prop_local_init_single(struct prop_local_single *pl)
-{
- raw_spin_lock_init(&pl->lock);
- pl->shift = 0;
- pl->period = 0;
- pl->events = 0;
- return 0;
-}
-
-void prop_local_destroy_single(struct prop_local_single *pl)
-{
-}
-
-/*
- * Catch up with missed period expirations.
- */
-static
-void prop_norm_single(struct prop_global *pg, struct prop_local_single *pl)
-{
- unsigned long period = 1UL << (pg->shift - 1);
- unsigned long period_mask = ~(period - 1);
- unsigned long global_period;
- unsigned long flags;
-
- global_period = percpu_counter_read(&pg->events);
- global_period &= period_mask;
-
- /*
- * Fast path - check if the local and global period count still match
- * outside of the lock.
- */
- if (pl->period == global_period)
- return;
-
- raw_spin_lock_irqsave(&pl->lock, flags);
- prop_adjust_shift(&pl->shift, &pl->period, pg->shift);
- /*
- * For each missed period, we half the local counter.
- */
- period = (global_period - pl->period) >> (pg->shift - 1);
- if (likely(period < BITS_PER_LONG))
- pl->events >>= period;
- else
- pl->events = 0;
- pl->period = global_period;
- raw_spin_unlock_irqrestore(&pl->lock, flags);
-}
-
-/*
- * ++x_{j}, ++t
- */
-void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
-{
- struct prop_global *pg = prop_get_global(pd);
-
- prop_norm_single(pg, pl);
- pl->events++;
- percpu_counter_add(&pg->events, 1);
- prop_put_global(pd, pg);
-}
-
-/*
- * Obtain a fraction of this proportion
- *
- * p_{j} = x_{j} / (period/2 + t % period/2)
- */
-void prop_fraction_single(struct prop_descriptor *pd,
- struct prop_local_single *pl,
- long *numerator, long *denominator)
-{
- struct prop_global *pg = prop_get_global(pd);
- unsigned long period_2 = 1UL << (pg->shift - 1);
- unsigned long counter_mask = period_2 - 1;
- unsigned long global_count;
-
- prop_norm_single(pg, pl);
- *numerator = pl->events;
-
- global_count = percpu_counter_read(&pg->events);
- *denominator = period_2 + (global_count & counter_mask);
-
- prop_put_global(pd, pg);
-}
VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
/*
* We can only reuse the page if nobody else maps the huge page or it's
- * part. We can do it by checking page_mapcount() on each sub-page, but
- * it's expensive.
- * The cheaper way is to check page_count() to be equal 1: every
- * mapcount takes page reference reference, so this way we can
- * guarantee, that the PMD is the only mapping.
- * This can give false negative if somebody pinned the page, but that's
- * fine.
+ * part.
*/
- if (page_mapcount(page) == 1 && page_count(page) == 1) {
+ if (page_trans_huge_mapcount(page, NULL) == 1) {
pmd_t entry;
entry = pmd_mkyoung(orig_pmd);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
if (pte_write(pteval)) {
writable = true;
} else {
- if (PageSwapCache(page) && !reuse_swap_page(page)) {
+ if (PageSwapCache(page) &&
+ !reuse_swap_page(page, NULL)) {
unlock_page(page);
result = SCAN_SWAP_CACHE_PAGE;
goto out;
return ret;
}
+/*
+ * This calculates accurately how many mappings a transparent hugepage
+ * has (unlike page_mapcount() which isn't fully accurate). This full
+ * accuracy is primarily needed to know if copy-on-write faults can
+ * reuse the page and change the mapping to read-write instead of
+ * copying them. At the same time this returns the total_mapcount too.
+ *
+ * The function returns the highest mapcount any one of the subpages
+ * has. If the return value is one, even if different processes are
+ * mapping different subpages of the transparent hugepage, they can
+ * all reuse it, because each process is reusing a different subpage.
+ *
+ * The total_mapcount is instead counting all virtual mappings of the
+ * subpages. If the total_mapcount is equal to "one", it tells the
+ * caller all mappings belong to the same "mm" and in turn the
+ * anon_vma of the transparent hugepage can become the vma->anon_vma
+ * local one as no other process may be mapping any of the subpages.
+ *
+ * It would be more accurate to replace page_mapcount() with
+ * page_trans_huge_mapcount(), however we only use
+ * page_trans_huge_mapcount() in the copy-on-write faults where we
+ * need full accuracy to avoid breaking page pinning, because
+ * page_trans_huge_mapcount() is slower than page_mapcount().
+ */
+int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
+{
+ int i, ret, _total_mapcount, mapcount;
+
+ /* hugetlbfs shouldn't call it */
+ VM_BUG_ON_PAGE(PageHuge(page), page);
+
+ if (likely(!PageTransCompound(page))) {
+ mapcount = atomic_read(&page->_mapcount) + 1;
+ if (total_mapcount)
+ *total_mapcount = mapcount;
+ return mapcount;
+ }
+
+ page = compound_head(page);
+
+ _total_mapcount = ret = 0;
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ mapcount = atomic_read(&page[i]._mapcount) + 1;
+ ret = max(ret, mapcount);
+ _total_mapcount += mapcount;
+ }
+ if (PageDoubleMap(page)) {
+ ret -= 1;
+ _total_mapcount -= HPAGE_PMD_NR;
+ }
+ mapcount = compound_mapcount(page);
+ ret += mapcount;
+ _total_mapcount += mapcount;
+ if (total_mapcount)
+ *total_mapcount = _total_mapcount;
+ return ret;
+}
+
/*
* This function splits huge page into normal pages. @page can point to any
* subpage of huge page to split. Split doesn't change the position of @page.
}
remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list);
+ up_read(&mm->mmap_sem);
spin_lock(&ksm_mmlist_lock);
ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next,
free_mm_slot(mm_slot);
clear_bit(MMF_VM_MERGEABLE, &mm->flags);
- up_read(&mm->mmap_sem);
mmdrop(mm);
- } else {
+ } else
spin_unlock(&ksm_mmlist_lock);
- up_read(&mm->mmap_sem);
- }
}
/* Clean up stable nodes, but don't worry if some are still busy */
up_read(&mm->mmap_sem);
mmdrop(mm);
} else {
- spin_unlock(&ksm_mmlist_lock);
up_read(&mm->mmap_sem);
+ /*
+ * up_read(&mm->mmap_sem) first because after
+ * spin_unlock(&ksm_mmlist_lock) run, the "mm" may
+ * already have been freed under us by __ksm_exit()
+ * because the "mm_slot" is still hashed and
+ * ksm_scan.mm_slot doesn't point to it anymore.
+ */
+ spin_unlock(&ksm_mmlist_lock);
}
/* Repeat until we've completed scanning the whole list */
* not dirty accountable.
*/
if (PageAnon(old_page) && !PageKsm(old_page)) {
+ int total_mapcount;
if (!trylock_page(old_page)) {
get_page(old_page);
pte_unmap_unlock(page_table, ptl);
}
put_page(old_page);
}
- if (reuse_swap_page(old_page)) {
- /*
- * The page is all ours. Move it to our anon_vma so
- * the rmap code will not search our parent or siblings.
- * Protected against the rmap code by the page lock.
- */
- page_move_anon_rmap(old_page, vma, address);
+ if (reuse_swap_page(old_page, &total_mapcount)) {
+ if (total_mapcount == 1) {
+ /*
+ * The page is all ours. Move it to
+ * our anon_vma so the rmap code will
+ * not search our parent or siblings.
+ * Protected against the rmap code by
+ * the page lock.
+ */
+ page_move_anon_rmap(compound_head(old_page),
+ vma, address);
+ }
unlock_page(old_page);
return wp_page_reuse(mm, vma, address, page_table, ptl,
orig_pte, old_page, 0, 0);
inc_mm_counter_fast(mm, MM_ANONPAGES);
dec_mm_counter_fast(mm, MM_SWAPENTS);
pte = mk_pte(page, vma->vm_page_prot);
- if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
+ if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
pte = maybe_mkwrite(pte_mkdirty(pte), vma);
flags &= ~FAULT_FLAG_WRITE;
ret |= VM_FAULT_WRITE;
* to it. And as a side-effect, free up its swap: because the old content
* on disk will never be read, and seeking back there to write new content
* later would only waste time away from clustering.
+ *
+ * NOTE: total_mapcount should not be relied upon by the caller if
+ * reuse_swap_page() returns false, but it may be always overwritten
+ * (see the other implementation for CONFIG_SWAP=n).
*/
-int reuse_swap_page(struct page *page)
+bool reuse_swap_page(struct page *page, int *total_mapcount)
{
int count;
VM_BUG_ON_PAGE(!PageLocked(page), page);
if (unlikely(PageKsm(page)))
- return 0;
- /* The page is part of THP and cannot be reused */
- if (PageTransCompound(page))
- return 0;
- count = page_mapcount(page);
+ return false;
+ count = page_trans_huge_mapcount(page, total_mapcount);
if (count <= 1 && PageSwapCache(page)) {
count += page_swapcount(page);
if (count == 1 && !PageWriteback(page)) {
static unsigned long zs_can_compact(struct size_class *class)
{
unsigned long obj_wasted;
+ unsigned long obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
+ unsigned long obj_used = zs_stat_get(class, OBJ_USED);
- obj_wasted = zs_stat_get(class, OBJ_ALLOCATED) -
- zs_stat_get(class, OBJ_USED);
+ if (obj_allocated <= obj_used)
+ return 0;
+ obj_wasted = obj_allocated - obj_used;
obj_wasted /= get_maxobj_per_zspage(class->size,
class->pages_per_zspage);
#include <asm/uaccess.h>
#include "br_private.h"
-/* called with RTNL */
static int get_bridge_ifindices(struct net *net, int *indices, int num)
{
struct net_device *dev;
int i = 0;
- for_each_netdev(net, dev) {
+ rcu_read_lock();
+ for_each_netdev_rcu(net, dev) {
if (i >= num)
break;
if (dev->priv_flags & IFF_EBRIDGE)
indices[i++] = dev->ifindex;
}
+ rcu_read_unlock();
return i;
}
struct br_ip saddr;
unsigned long max_delay;
unsigned long now = jiffies;
+ unsigned int offset = skb_transport_offset(skb);
__be32 group;
int err = 0;
group = ih->group;
- if (skb->len == sizeof(*ih)) {
+ if (skb->len == offset + sizeof(*ih)) {
max_delay = ih->code * (HZ / IGMP_TIMER_SCALE);
if (!max_delay) {
max_delay = 10 * HZ;
group = 0;
}
- } else if (skb->len >= sizeof(*ih3)) {
+ } else if (skb->len >= offset + sizeof(*ih3)) {
ih3 = igmpv3_query_hdr(skb);
if (ih3->nsrcs)
goto out;
struct br_ip saddr;
unsigned long max_delay;
unsigned long now = jiffies;
+ unsigned int offset = skb_transport_offset(skb);
const struct in6_addr *group = NULL;
bool is_general_query;
int err = 0;
(port && port->state == BR_STATE_DISABLED))
goto out;
- if (skb->len == sizeof(*mld)) {
- if (!pskb_may_pull(skb, sizeof(*mld))) {
+ if (skb->len == offset + sizeof(*mld)) {
+ if (!pskb_may_pull(skb, offset + sizeof(*mld))) {
err = -EINVAL;
goto out;
}
if (max_delay)
group = &mld->mld_mca;
} else {
- if (!pskb_may_pull(skb, sizeof(*mld2q))) {
+ if (!pskb_may_pull(skb, offset + sizeof(*mld2q))) {
err = -EINVAL;
goto out;
}
list_splice_tail_init(&xfrm->flow_cache_gc_list, &gc_list);
spin_unlock_bh(&xfrm->flow_cache_gc_lock);
- list_for_each_entry_safe(fce, n, &gc_list, u.gc_list)
+ list_for_each_entry_safe(fce, n, &gc_list, u.gc_list) {
flow_entry_kill(fce, xfrm);
+ atomic_dec(&xfrm->flow_cache_gc_count);
+ WARN_ON(atomic_read(&xfrm->flow_cache_gc_count) < 0);
+ }
}
static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
struct netns_xfrm *xfrm)
{
if (deleted) {
+ atomic_add(deleted, &xfrm->flow_cache_gc_count);
fcp->hash_count -= deleted;
spin_lock_bh(&xfrm->flow_cache_gc_lock);
list_splice_tail(gc_list, &xfrm->flow_cache_gc_list);
if (fcp->hash_count > fc->high_watermark)
flow_cache_shrink(fc, fcp);
+ if (fcp->hash_count > 2 * fc->high_watermark ||
+ atomic_read(&net->xfrm.flow_cache_gc_count) > fc->high_watermark) {
+ atomic_inc(&net->xfrm.flow_cache_genid);
+ flo = ERR_PTR(-ENOBUFS);
+ goto ret_object;
+ }
+
fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
if (fle) {
fle->net = net;
INIT_WORK(&net->xfrm.flow_cache_gc_work, flow_cache_gc_task);
INIT_WORK(&net->xfrm.flow_cache_flush_work, flow_cache_flush_task);
mutex_init(&net->xfrm.flow_flush_sem);
+ atomic_set(&net->xfrm.flow_cache_gc_count, 0);
fc->hash_shift = 10;
fc->low_watermark = 2 * flow_cache_hash_size(fc);
static int rtnl_fill_link_ifmap(struct sk_buff *skb, struct net_device *dev)
{
- struct rtnl_link_ifmap map = {
- .mem_start = dev->mem_start,
- .mem_end = dev->mem_end,
- .base_addr = dev->base_addr,
- .irq = dev->irq,
- .dma = dev->dma,
- .port = dev->if_port,
- };
+ struct rtnl_link_ifmap map;
+
+ memset(&map, 0, sizeof(map));
+ map.mem_start = dev->mem_start;
+ map.mem_end = dev->mem_end;
+ map.base_addr = dev->base_addr;
+ map.irq = dev->irq;
+ map.dma = dev->dma;
+ map.port = dev->if_port;
+
if (nla_put(skb, IFLA_MAP, sizeof(map), &map))
return -EMSGSIZE;
val = 65535 - 40;
if (type == RTAX_MTU && val > 65535 - 15)
val = 65535 - 15;
+ if (type == RTAX_HOPLIMIT && val > 255)
+ val = 255;
if (type == RTAX_FEATURES && (val & ~RTAX_FEATURE_MASK))
return -EINVAL;
fi->fib_metrics[type - 1] = val;
int err = -ENOSYS;
const struct net_offload **offloads;
- udp_tunnel_gro_complete(skb, nhoff);
-
rcu_read_lock();
offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;
ops = rcu_dereference(offloads[proto]);
err = ops->callbacks.gro_complete(skb, nhoff);
+ skb_set_inner_mac_header(skb, nhoff);
+
out_unlock:
rcu_read_unlock();
err = ops->callbacks.gro_complete(skb, nhoff + guehlen);
+ skb_set_inner_mac_header(skb, nhoff + guehlen);
+
out_unlock:
rcu_read_unlock();
return err;
iph->saddr, iph->daddr, tpi->key);
if (tunnel) {
- skb_pop_mac_header(skb);
+ if (tunnel->dev->type != ARPHRD_NONE)
+ skb_pop_mac_header(skb);
+ else
+ skb_reset_mac_header(skb);
if (tunnel->collect_md) {
__be16 flags;
__be64 tun_id;
struct ip_tunnel *t = netdev_priv(dev);
t->collect_md = true;
+ if (dev->type == ARPHRD_IPGRE)
+ dev->type = ARPHRD_NONE;
}
}
struct dst_entry *dst = skb_dst(skb);
struct net_device *tdev; /* Device to other host */
int err;
+ int mtu;
if (!dst) {
dev->stats.tx_carrier_errors++;
tunnel->err_count = 0;
}
+ mtu = dst_mtu(dst);
+ if (skb->len > mtu) {
+ skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
+ if (skb->protocol == htons(ETH_P_IP)) {
+ icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
+ htonl(mtu));
+ } else {
+ if (mtu < IPV6_MIN_MTU)
+ mtu = IPV6_MIN_MTU;
+
+ icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
+ }
+
+ dst_release(dst);
+ goto tx_error;
+ }
+
skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(dev)));
skb_dst_set(skb, dst);
skb->dev = skb_dst(skb)->dev;
*/
if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
skb_headroom(skb) >= 0xFFFF)) {
- struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
- GFP_ATOMIC);
+ struct sk_buff *nskb;
+
+ skb_mstamp_get(&skb->skb_mstamp);
+ nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
-ENOBUFS;
} else {
uh->len = newlen;
+ /* Set encapsulation before calling into inner gro_complete() functions
+ * to make them set up the inner offsets.
+ */
+ skb->encapsulation = 1;
+
rcu_read_lock();
uo_priv = rcu_dereference(udp_offload_base);
if (skb->remcsum_offload)
skb_shinfo(skb)->gso_type |= SKB_GSO_TUNNEL_REMCSUM;
- skb->encapsulation = 1;
- skb_set_inner_mac_header(skb, nhoff + sizeof(struct udphdr));
-
return err;
}
if (__ipv6_addr_needs_scope_id(addr_type))
iif = skb->dev->ifindex;
+ else
+ iif = l3mdev_master_ifindex(skb->dev);
/*
* Must not send error if the source does not uniquely
else if (!fl6.flowi6_oif)
fl6.flowi6_oif = np->ucast_oif;
- if (!fl6.flowi6_oif)
- fl6.flowi6_oif = l3mdev_master_ifindex(skb->dev);
-
dst = icmpv6_route_lookup(net, skb, sk, &fl6);
if (IS_ERR(dst))
goto out;
} else {
val = nla_get_u32(nla);
}
+ if (type == RTAX_HOPLIMIT && val > 255)
+ val = 255;
if (type == RTAX_FEATURES && (val & ~RTAX_FEATURE_MASK))
goto err;
fl6.flowi6_proto = IPPROTO_TCP;
if (rt6_need_strict(&fl6.daddr) && !oif)
fl6.flowi6_oif = tcp_v6_iif(skb);
- else
+ else {
+ if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
+ oif = skb->skb_iif;
+
fl6.flowi6_oif = oif;
+ }
+
fl6.flowi6_mark = IP6_REPLY_MARK(net, skb->mark);
fl6.fl6_dport = t1->dest;
fl6.fl6_sport = t1->source;
if (llc->cmsg_flags & LLC_CMSG_PKTINFO) {
struct llc_pktinfo info;
+ memset(&info, 0, sizeof(info));
info.lpi_ifindex = llc_sk(skb->sk)->dev->ifindex;
llc_pdu_decode_dsap(skb, &info.lpi_sap);
llc_pdu_decode_da(skb, info.lpi_mac);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(nf_conntrack_expect_lock);
EXPORT_SYMBOL_GPL(nf_conntrack_expect_lock);
-static __read_mostly spinlock_t nf_conntrack_locks_all_lock;
+static __read_mostly DEFINE_SPINLOCK(nf_conntrack_locks_all_lock);
static __read_mostly bool nf_conntrack_locks_all;
void nf_conntrack_lock(spinlock_t *lock) __acquires(lock)
int nf_conntrack_init_net(struct net *net)
{
+ static atomic64_t unique_id;
int ret = -ENOMEM;
int cpu;
if (!net->ct.stat)
goto err_pcpu_lists;
- net->ct.slabname = kasprintf(GFP_KERNEL, "nf_conntrack_%p", net);
+ net->ct.slabname = kasprintf(GFP_KERNEL, "nf_conntrack_%llu",
+ (u64)atomic64_inc_return(&unique_id));
if (!net->ct.slabname)
goto err_slabname;
return -EINVAL;
if (flags & NFACCT_F_OVERQUOTA)
return -EINVAL;
+ if ((flags & NFACCT_F_QUOTA) && !tb[NFACCT_QUOTA])
+ return -EINVAL;
size += sizeof(u64);
}
list_del(&info->timer->entry);
del_timer_sync(&info->timer->timer);
+ cancel_work_sync(&info->timer->work);
sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr);
kfree(info->timer->attr.attr.name);
kfree(info->timer);
return -EINVAL;
}
+ /* Userspace may decide to perform a ct lookup without a helper
+ * specified followed by a (recirculate and) commit with one.
+ * Therefore, for unconfirmed connections which we will commit,
+ * we need to attach the helper here.
+ */
+ if (!nf_ct_is_confirmed(ct) && info->commit &&
+ info->helper && !nfct_help(ct)) {
+ int err = __nf_ct_try_assign_helper(ct, info->ct,
+ GFP_ATOMIC);
+ if (err)
+ return err;
+ }
+
/* Call the helper only if:
* - nf_conntrack_in() was executed above ("!cached") for a
* confirmed connection, or
u16 ife_type = 0;
u8 *daddr = NULL;
u8 *saddr = NULL;
- int ret = 0;
+ int ret = 0, exists = 0;
int err;
err = nla_parse_nested(tb, TCA_IFE_MAX, nla, ife_policy);
parm = nla_data(tb[TCA_IFE_PARMS]);
+ exists = tcf_hash_check(tn, parm->index, a, bind);
+ if (exists && bind)
+ return 0;
+
if (parm->flags & IFE_ENCODE) {
/* Until we get issued the ethertype, we cant have
* a default..
**/
if (!tb[TCA_IFE_TYPE]) {
+ if (exists)
+ tcf_hash_release(a, bind);
pr_info("You MUST pass etherype for encoding\n");
return -EINVAL;
}
}
- if (!tcf_hash_check(tn, parm->index, a, bind)) {
+ if (!exists) {
ret = tcf_hash_create(tn, parm->index, est, a, sizeof(*ife),
bind, false);
if (ret)
return ret;
ret = ACT_P_CREATED;
} else {
- if (bind) /* dont override defaults */
- return 0;
tcf_hash_release(a, bind);
if (!ovr)
return -EEXIST;
NULL);
if (err) {
metadata_parse_err:
+ if (exists)
+ tcf_hash_release(a, bind);
if (ret == ACT_P_CREATED)
_tcf_ife_cleanup(a, bind);
struct tcf_ipt *ipt;
struct xt_entry_target *td, *t;
char *tname;
- int ret = 0, err;
+ int ret = 0, err, exists = 0;
u32 hook = 0;
u32 index = 0;
if (err < 0)
return err;
- if (tb[TCA_IPT_HOOK] == NULL)
- return -EINVAL;
- if (tb[TCA_IPT_TARG] == NULL)
+ if (tb[TCA_IPT_INDEX] != NULL)
+ index = nla_get_u32(tb[TCA_IPT_INDEX]);
+
+ exists = tcf_hash_check(tn, index, a, bind);
+ if (exists && bind)
+ return 0;
+
+ if (tb[TCA_IPT_HOOK] == NULL || tb[TCA_IPT_TARG] == NULL) {
+ if (exists)
+ tcf_hash_release(a, bind);
return -EINVAL;
+ }
td = (struct xt_entry_target *)nla_data(tb[TCA_IPT_TARG]);
if (nla_len(tb[TCA_IPT_TARG]) < td->u.target_size)
return -EINVAL;
- if (tb[TCA_IPT_INDEX] != NULL)
- index = nla_get_u32(tb[TCA_IPT_INDEX]);
-
if (!tcf_hash_check(tn, index, a, bind)) {
ret = tcf_hash_create(tn, index, est, a, sizeof(*ipt), bind,
false);
struct tc_mirred *parm;
struct tcf_mirred *m;
struct net_device *dev;
- int ret, ok_push = 0;
+ int ret, ok_push = 0, exists = 0;
if (nla == NULL)
return -EINVAL;
if (tb[TCA_MIRRED_PARMS] == NULL)
return -EINVAL;
parm = nla_data(tb[TCA_MIRRED_PARMS]);
+
+ exists = tcf_hash_check(tn, parm->index, a, bind);
+ if (exists && bind)
+ return 0;
+
switch (parm->eaction) {
case TCA_EGRESS_MIRROR:
case TCA_EGRESS_REDIR:
break;
default:
+ if (exists)
+ tcf_hash_release(a, bind);
return -EINVAL;
}
if (parm->ifindex) {
dev = __dev_get_by_index(net, parm->ifindex);
- if (dev == NULL)
+ if (dev == NULL) {
+ if (exists)
+ tcf_hash_release(a, bind);
return -ENODEV;
+ }
switch (dev->type) {
case ARPHRD_TUNNEL:
case ARPHRD_TUNNEL6:
dev = NULL;
}
- if (!tcf_hash_check(tn, parm->index, a, bind)) {
+ if (!exists) {
if (dev == NULL)
return -EINVAL;
ret = tcf_hash_create(tn, parm->index, est, a,
return ret;
ret = ACT_P_CREATED;
} else {
- if (bind)
- return 0;
-
tcf_hash_release(a, bind);
if (!ovr)
return -EEXIST;
struct tc_defact *parm;
struct tcf_defact *d;
char *defdata;
- int ret = 0, err;
+ int ret = 0, err, exists = 0;
if (nla == NULL)
return -EINVAL;
if (tb[TCA_DEF_PARMS] == NULL)
return -EINVAL;
- if (tb[TCA_DEF_DATA] == NULL)
- return -EINVAL;
parm = nla_data(tb[TCA_DEF_PARMS]);
+ exists = tcf_hash_check(tn, parm->index, a, bind);
+ if (exists && bind)
+ return 0;
+
+ if (tb[TCA_DEF_DATA] == NULL) {
+ if (exists)
+ tcf_hash_release(a, bind);
+ return -EINVAL;
+ }
+
defdata = nla_data(tb[TCA_DEF_DATA]);
- if (!tcf_hash_check(tn, parm->index, a, bind)) {
+ if (!exists) {
ret = tcf_hash_create(tn, parm->index, est, a,
sizeof(*d), bind, false);
if (ret)
} else {
d = to_defact(a);
- if (bind)
- return 0;
tcf_hash_release(a, bind);
if (!ovr)
return -EEXIST;
struct tcf_skbedit *d;
u32 flags = 0, *priority = NULL, *mark = NULL;
u16 *queue_mapping = NULL;
- int ret = 0, err;
+ int ret = 0, err, exists = 0;
if (nla == NULL)
return -EINVAL;
mark = nla_data(tb[TCA_SKBEDIT_MARK]);
}
- if (!flags)
- return -EINVAL;
-
parm = nla_data(tb[TCA_SKBEDIT_PARMS]);
- if (!tcf_hash_check(tn, parm->index, a, bind)) {
+ exists = tcf_hash_check(tn, parm->index, a, bind);
+ if (exists && bind)
+ return 0;
+
+ if (!flags) {
+ tcf_hash_release(a, bind);
+ return -EINVAL;
+ }
+
+ if (!exists) {
ret = tcf_hash_create(tn, parm->index, est, a,
sizeof(*d), bind, false);
if (ret)
ret = ACT_P_CREATED;
} else {
d = to_skbedit(a);
- if (bind)
- return 0;
tcf_hash_release(a, bind);
if (!ovr)
return -EEXIST;
int action;
__be16 push_vid = 0;
__be16 push_proto = 0;
- int ret = 0;
+ int ret = 0, exists = 0;
int err;
if (!nla)
if (!tb[TCA_VLAN_PARMS])
return -EINVAL;
parm = nla_data(tb[TCA_VLAN_PARMS]);
+ exists = tcf_hash_check(tn, parm->index, a, bind);
+ if (exists && bind)
+ return 0;
+
switch (parm->v_action) {
case TCA_VLAN_ACT_POP:
break;
case TCA_VLAN_ACT_PUSH:
- if (!tb[TCA_VLAN_PUSH_VLAN_ID])
+ if (!tb[TCA_VLAN_PUSH_VLAN_ID]) {
+ if (exists)
+ tcf_hash_release(a, bind);
return -EINVAL;
+ }
push_vid = nla_get_u16(tb[TCA_VLAN_PUSH_VLAN_ID]);
- if (push_vid >= VLAN_VID_MASK)
+ if (push_vid >= VLAN_VID_MASK) {
+ if (exists)
+ tcf_hash_release(a, bind);
return -ERANGE;
+ }
if (tb[TCA_VLAN_PUSH_VLAN_PROTOCOL]) {
push_proto = nla_get_be16(tb[TCA_VLAN_PUSH_VLAN_PROTOCOL]);
}
break;
default:
+ if (exists)
+ tcf_hash_release(a, bind);
return -EINVAL;
}
action = parm->v_action;
- if (!tcf_hash_check(tn, parm->index, a, bind)) {
+ if (!exists) {
ret = tcf_hash_create(tn, parm->index, est, a,
sizeof(*v), bind, false);
if (ret)
ret = ACT_P_CREATED;
} else {
- if (bind)
- return 0;
tcf_hash_release(a, bind);
if (!ovr)
return -EEXIST;
else if (sk->sk_shutdown & RCV_SHUTDOWN)
err = 0;
- if (copied > 0) {
- /* We only do these additional bookkeeping/notification steps
- * if we actually copied something out of the queue pair
- * instead of just peeking ahead.
- */
-
- if (!(flags & MSG_PEEK)) {
- /* If the other side has shutdown for sending and there
- * is nothing more to read, then modify the socket
- * state.
- */
- if (vsk->peer_shutdown & SEND_SHUTDOWN) {
- if (vsock_stream_has_data(vsk) <= 0) {
- sk->sk_state = SS_UNCONNECTED;
- sock_set_flag(sk, SOCK_DONE);
- sk->sk_state_change(sk);
- }
- }
- }
+ if (copied > 0)
err = copied;
- }
out:
release_sock(sk);
memset(&theirs, 0, sizeof(theirs));
memcpy(new, ours, sizeof(*new));
+ memset(dte, 0, sizeof(*dte));
len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
if (len < 0)
skb_dst_force(skb);
+ /* Inner headers are invalid now. */
+ skb->encapsulation = 0;
+
err = x->type->output(x, skb);
if (err == -EINPROGRESS)
goto out;
goto error;
}
err = snd_hda_codec_configure(codec);
- if (err < 0)
- goto error;
- /* rebuild PCMs */
- err = snd_hda_codec_build_pcms(codec);
- if (err < 0)
- goto error;
- /* rebuild mixers */
- err = snd_hda_codec_build_controls(codec);
if (err < 0)
goto error;
err = snd_card_register(codec->card);
spec->ops.pin_hbr_setup = atihdmi_pin_hbr_setup;
spec->ops.setup_stream = atihdmi_setup_stream;
+ spec->chmap.ops.pin_get_slot_channel = atihdmi_pin_get_slot_channel;
+ spec->chmap.ops.pin_set_slot_channel = atihdmi_pin_set_slot_channel;
+
if (!has_amd_full_remap_support(codec)) {
/* override to ATI/AMD-specific versions with pairwise mapping */
spec->chmap.ops.chmap_cea_alloc_validate_get_type =
spec->chmap.ops.cea_alloc_to_tlv_chmap =
atihdmi_paired_cea_alloc_to_tlv_chmap;
spec->chmap.ops.chmap_validate = atihdmi_paired_chmap_validate;
- spec->chmap.ops.pin_get_slot_channel =
- atihdmi_pin_get_slot_channel;
- spec->chmap.ops.pin_set_slot_channel =
- atihdmi_pin_set_slot_channel;
}
/* ATI/AMD converters do not advertise all of their capabilities */
ALC668_FIXUP_DELL_DISABLE_AAMIX,
ALC668_FIXUP_DELL_XPS13,
ALC662_FIXUP_ASUS_Nx50,
+ ALC668_FIXUP_ASUS_Nx51,
};
static const struct hda_fixup alc662_fixups[] = {
.chained = true,
.chain_id = ALC662_FIXUP_BASS_1A
},
+ [ALC668_FIXUP_ASUS_Nx51] = {
+ .type = HDA_FIXUP_PINS,
+ .v.pins = (const struct hda_pintbl[]) {
+ {0x1a, 0x90170151}, /* bass speaker */
+ {}
+ },
+ .chained = true,
+ .chain_id = ALC662_FIXUP_BASS_CHMAP,
+ },
};
static const struct snd_pci_quirk alc662_fixup_tbl[] = {
SND_PCI_QUIRK(0x1028, 0x0698, "Dell", ALC668_FIXUP_DELL_MIC_NO_PRESENCE),
SND_PCI_QUIRK(0x1028, 0x069f, "Dell", ALC668_FIXUP_DELL_MIC_NO_PRESENCE),
SND_PCI_QUIRK(0x103c, 0x1632, "HP RP5800", ALC662_FIXUP_HP_RP5800),
+ SND_PCI_QUIRK(0x1043, 0x1080, "Asus UX501VW", ALC668_FIXUP_HEADSET_MODE),
SND_PCI_QUIRK(0x1043, 0x11cd, "Asus N550", ALC662_FIXUP_ASUS_Nx50),
SND_PCI_QUIRK(0x1043, 0x13df, "Asus N550JX", ALC662_FIXUP_BASS_1A),
SND_PCI_QUIRK(0x1043, 0x129d, "Asus N750", ALC662_FIXUP_ASUS_Nx50),
SND_PCI_QUIRK(0x1043, 0x1477, "ASUS N56VZ", ALC662_FIXUP_BASS_MODE4_CHMAP),
SND_PCI_QUIRK(0x1043, 0x15a7, "ASUS UX51VZH", ALC662_FIXUP_BASS_16),
+ SND_PCI_QUIRK(0x1043, 0x177d, "ASUS N551", ALC668_FIXUP_ASUS_Nx51),
+ SND_PCI_QUIRK(0x1043, 0x17bd, "ASUS N751", ALC668_FIXUP_ASUS_Nx51),
SND_PCI_QUIRK(0x1043, 0x1b73, "ASUS N55SF", ALC662_FIXUP_BASS_16),
SND_PCI_QUIRK(0x1043, 0x1bf3, "ASUS N76VZ", ALC662_FIXUP_BASS_MODE4_CHMAP),
SND_PCI_QUIRK(0x1043, 0x8469, "ASUS mobo", ALC662_FIXUP_NO_JACK_DETECT),
case USB_ID(0x047F, 0x0415): /* Plantronics BT-300 */
case USB_ID(0x047F, 0xAA05): /* Plantronics DA45 */
case USB_ID(0x04D8, 0xFEEA): /* Benchmark DAC1 Pre */
+ case USB_ID(0x0556, 0x0014): /* Phoenix Audio TMX320VC */
case USB_ID(0x074D, 0x3553): /* Outlaw RR2150 (Micronas UAC3553B) */
+ case USB_ID(0x1de7, 0x0013): /* Phoenix Audio MT202exe */
case USB_ID(0x1de7, 0x0014): /* Phoenix Audio TMX320 */
+ case USB_ID(0x1de7, 0x0114): /* Phoenix Audio MT202pcs */
case USB_ID(0x21B4, 0x0081): /* AudioQuest DragonFly */
return true;
}
FEATURE_TESTS_BASIC := \
backtrace \
dwarf \
+ dwarf_getlocations \
fortify-source \
sync-compare-and-swap \
glibc \
FEATURE_DISPLAY ?= \
dwarf \
+ dwarf_getlocations \
glibc \
gtk2 \
libaudit \
test-backtrace.bin \
test-bionic.bin \
test-dwarf.bin \
+ test-dwarf_getlocations.bin \
test-fortify-source.bin \
test-sync-compare-and-swap.bin \
test-glibc.bin \
$(OUTPUT)test-dwarf.bin:
$(BUILD) $(DWARFLIBS)
+$(OUTPUT)test-dwarf_getlocations.bin:
+ $(BUILD) $(DWARFLIBS)
+
$(OUTPUT)test-libelf-mmap.bin:
$(BUILD) -lelf
# include "test-dwarf.c"
#undef main
+#define main main_test_dwarf_getlocations
+# include "test-dwarf_getlocations.c"
+#undef main
+
#define main main_test_libelf_getphdrnum
# include "test-libelf-getphdrnum.c"
#undef main
main_test_libelf_mmap();
main_test_glibc();
main_test_dwarf();
+ main_test_dwarf_getlocations();
main_test_libelf_getphdrnum();
main_test_libunwind();
main_test_libaudit();
--- /dev/null
+#include <stdlib.h>
+#include <elfutils/libdw.h>
+
+int main(void)
+{
+ Dwarf_Addr base, start, end;
+ Dwarf_Attribute attr;
+ Dwarf_Op *op;
+ size_t nops;
+ ptrdiff_t offset = 0;
+ return (int)dwarf_getlocations(&attr, offset, &base, &start, &end, &op, &nops);
+}
current_op = current_exp;
ret = collapse_tree(current_op, parg, error_str);
+ /* collapse_tree() may free current_op, and updates parg accordingly */
+ current_op = NULL;
if (ret < 0)
goto fail;
- *parg = current_op;
-
free(token);
return 0;
char *buff;
len = klogctl(CMD_ACTION_SIZE_BUFFER, NULL, 0);
+ if (len < 0)
+ return NULL;
+
buff = malloc(len);
if (!buff)
return NULL;
# define REG_OFFSET_NAME_32(n, r) {.name = n, .offset = offsetof(struct pt_regs, r)}
#endif
+/* TODO: switching by dwarf address size */
+#ifndef __x86_64__
static const struct pt_regs_offset x86_32_regoffset_table[] = {
REG_OFFSET_NAME_32("%ax", eax),
REG_OFFSET_NAME_32("%cx", ecx),
REG_OFFSET_END,
};
+#define regoffset_table x86_32_regoffset_table
+#else
static const struct pt_regs_offset x86_64_regoffset_table[] = {
REG_OFFSET_NAME_64("%ax", rax),
REG_OFFSET_NAME_64("%dx", rdx),
REG_OFFSET_END,
};
-/* TODO: switching by dwarf address size */
-#ifdef __x86_64__
#define regoffset_table x86_64_regoffset_table
-#else
-#define regoffset_table x86_32_regoffset_table
#endif
/* Minus 1 for the ending REG_OFFSET_END */
return S_ISDIR(st.st_mode);
}
-#define for_each_lang(scripts_path, scripts_dir, lang_dirent, lang_next)\
- while (!readdir_r(scripts_dir, &lang_dirent, &lang_next) && \
- lang_next) \
- if ((lang_dirent.d_type == DT_DIR || \
- (lang_dirent.d_type == DT_UNKNOWN && \
- is_directory(scripts_path, &lang_dirent))) && \
- (strcmp(lang_dirent.d_name, ".")) && \
- (strcmp(lang_dirent.d_name, "..")))
-
-#define for_each_script(lang_path, lang_dir, script_dirent, script_next)\
- while (!readdir_r(lang_dir, &script_dirent, &script_next) && \
- script_next) \
- if (script_dirent.d_type != DT_DIR && \
- (script_dirent.d_type != DT_UNKNOWN || \
- !is_directory(lang_path, &script_dirent)))
+#define for_each_lang(scripts_path, scripts_dir, lang_dirent) \
+ while ((lang_dirent = readdir(scripts_dir)) != NULL) \
+ if ((lang_dirent->d_type == DT_DIR || \
+ (lang_dirent->d_type == DT_UNKNOWN && \
+ is_directory(scripts_path, lang_dirent))) && \
+ (strcmp(lang_dirent->d_name, ".")) && \
+ (strcmp(lang_dirent->d_name, "..")))
+
+#define for_each_script(lang_path, lang_dir, script_dirent) \
+ while ((script_dirent = readdir(lang_dir)) != NULL) \
+ if (script_dirent->d_type != DT_DIR && \
+ (script_dirent->d_type != DT_UNKNOWN || \
+ !is_directory(lang_path, script_dirent)))
#define RECORD_SUFFIX "-record"
const char *s __maybe_unused,
int unset __maybe_unused)
{
- struct dirent *script_next, *lang_next, script_dirent, lang_dirent;
+ struct dirent *script_dirent, *lang_dirent;
char scripts_path[MAXPATHLEN];
DIR *scripts_dir, *lang_dir;
char script_path[MAXPATHLEN];
if (!scripts_dir)
return -1;
- for_each_lang(scripts_path, scripts_dir, lang_dirent, lang_next) {
+ for_each_lang(scripts_path, scripts_dir, lang_dirent) {
snprintf(lang_path, MAXPATHLEN, "%s/%s/bin", scripts_path,
- lang_dirent.d_name);
+ lang_dirent->d_name);
lang_dir = opendir(lang_path);
if (!lang_dir)
continue;
- for_each_script(lang_path, lang_dir, script_dirent, script_next) {
- script_root = get_script_root(&script_dirent, REPORT_SUFFIX);
+ for_each_script(lang_path, lang_dir, script_dirent) {
+ script_root = get_script_root(script_dirent, REPORT_SUFFIX);
if (script_root) {
desc = script_desc__findnew(script_root);
snprintf(script_path, MAXPATHLEN, "%s/%s",
- lang_path, script_dirent.d_name);
+ lang_path, script_dirent->d_name);
read_script_info(desc, script_path);
free(script_root);
}
*/
int find_scripts(char **scripts_array, char **scripts_path_array)
{
- struct dirent *script_next, *lang_next, script_dirent, lang_dirent;
+ struct dirent *script_dirent, *lang_dirent;
char scripts_path[MAXPATHLEN], lang_path[MAXPATHLEN];
DIR *scripts_dir, *lang_dir;
struct perf_session *session;
return -1;
}
- for_each_lang(scripts_path, scripts_dir, lang_dirent, lang_next) {
+ for_each_lang(scripts_path, scripts_dir, lang_dirent) {
snprintf(lang_path, MAXPATHLEN, "%s/%s", scripts_path,
- lang_dirent.d_name);
+ lang_dirent->d_name);
#ifdef NO_LIBPERL
if (strstr(lang_path, "perl"))
continue;
if (!lang_dir)
continue;
- for_each_script(lang_path, lang_dir, script_dirent, script_next) {
+ for_each_script(lang_path, lang_dir, script_dirent) {
/* Skip those real time scripts: xxxtop.p[yl] */
- if (strstr(script_dirent.d_name, "top."))
+ if (strstr(script_dirent->d_name, "top."))
continue;
sprintf(scripts_path_array[i], "%s/%s", lang_path,
- script_dirent.d_name);
- temp = strchr(script_dirent.d_name, '.');
+ script_dirent->d_name);
+ temp = strchr(script_dirent->d_name, '.');
snprintf(scripts_array[i],
- (temp - script_dirent.d_name) + 1,
- "%s", script_dirent.d_name);
+ (temp - script_dirent->d_name) + 1,
+ "%s", script_dirent->d_name);
if (check_ev_match(lang_path,
scripts_array[i], session))
static char *get_script_path(const char *script_root, const char *suffix)
{
- struct dirent *script_next, *lang_next, script_dirent, lang_dirent;
+ struct dirent *script_dirent, *lang_dirent;
char scripts_path[MAXPATHLEN];
char script_path[MAXPATHLEN];
DIR *scripts_dir, *lang_dir;
if (!scripts_dir)
return NULL;
- for_each_lang(scripts_path, scripts_dir, lang_dirent, lang_next) {
+ for_each_lang(scripts_path, scripts_dir, lang_dirent) {
snprintf(lang_path, MAXPATHLEN, "%s/%s/bin", scripts_path,
- lang_dirent.d_name);
+ lang_dirent->d_name);
lang_dir = opendir(lang_path);
if (!lang_dir)
continue;
- for_each_script(lang_path, lang_dir, script_dirent, script_next) {
- __script_root = get_script_root(&script_dirent, suffix);
+ for_each_script(lang_path, lang_dir, script_dirent) {
+ __script_root = get_script_root(script_dirent, suffix);
if (__script_root && !strcmp(script_root, __script_root)) {
free(__script_root);
closedir(lang_dir);
closedir(scripts_dir);
snprintf(script_path, MAXPATHLEN, "%s/%s",
- lang_path, script_dirent.d_name);
+ lang_path, script_dirent->d_name);
return strdup(script_path);
}
free(__script_root);
perf_evlist__set_leader(evsel_list);
evlist__for_each(evsel_list, counter) {
+try_again:
if (create_perf_stat_counter(counter) < 0) {
/*
* PPC returns ENXIO for HW counters until 2.6.37
if ((counter->leader != counter) ||
!(counter->leader->nr_members > 1))
continue;
- }
+ } else if (perf_evsel__fallback(counter, errno, msg, sizeof(msg))) {
+ if (verbose)
+ ui__warning("%s\n", msg);
+ goto try_again;
+ }
perf_evsel__open_strerror(counter, &target,
errno, msg, sizeof(msg));
ifneq ($(feature-dwarf), 1)
msg := $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev);
NO_DWARF := 1
+ else
+ ifneq ($(feature-dwarf_getlocations), 1)
+ msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157);
+ else
+ CFLAGS += -DHAVE_DWARF_GETLOCATIONS
+ endif # dwarf_getlocations
endif # Dwarf support
endif # libelf support
endif # NO_LIBELF
return 0;
}
+#ifdef HAVE_DWARF_GETLOCATIONS
/**
* die_get_var_innermost_scope - Get innermost scope range of given variable DIE
* @sp_die: a subprogram DIE
return ret;
}
+#else
+int die_get_var_range(Dwarf_Die *sp_die __maybe_unused,
+ Dwarf_Die *vr_die __maybe_unused,
+ struct strbuf *buf __maybe_unused)
+{
+ return -ENOTSUP;
+}
+#endif
{
char filename[PATH_MAX];
DIR *tasks;
- struct dirent dirent, *next;
+ struct dirent *dirent;
pid_t tgid, ppid;
int rc = 0;
return 0;
}
- while (!readdir_r(tasks, &dirent, &next) && next) {
+ while ((dirent = readdir(tasks)) != NULL) {
char *end;
pid_t _pid;
- _pid = strtol(dirent.d_name, &end, 10);
+ _pid = strtol(dirent->d_name, &end, 10);
if (*end)
continue;
{
DIR *proc;
char proc_path[PATH_MAX];
- struct dirent dirent, *next;
+ struct dirent *dirent;
union perf_event *comm_event, *mmap_event, *fork_event;
int err = -1;
if (proc == NULL)
goto out_free_fork;
- while (!readdir_r(proc, &dirent, &next) && next) {
+ while ((dirent = readdir(proc)) != NULL) {
char *end;
- pid_t pid = strtol(dirent.d_name, &end, 10);
+ pid_t pid = strtol(dirent->d_name, &end, 10);
if (*end) /* only interested in proper numerical dirents */
continue;
bool perf_evsel__fallback(struct perf_evsel *evsel, int err,
char *msg, size_t msgsize)
{
+ int paranoid;
+
if ((err == ENOENT || err == ENXIO || err == ENODEV) &&
evsel->attr.type == PERF_TYPE_HARDWARE &&
evsel->attr.config == PERF_COUNT_HW_CPU_CYCLES) {
evsel->attr.config = PERF_COUNT_SW_CPU_CLOCK;
zfree(&evsel->name);
+ return true;
+ } else if (err == EACCES && !evsel->attr.exclude_kernel &&
+ (paranoid = perf_event_paranoid()) > 1) {
+ const char *name = perf_evsel__name(evsel);
+ char *new_name;
+
+ if (asprintf(&new_name, "%s%su", name, strchr(name, ':') ? "" : ":") < 0)
+ return false;
+
+ if (evsel->name)
+ free(evsel->name);
+ evsel->name = new_name;
+ scnprintf(msg, msgsize,
+"kernel.perf_event_paranoid=%d, trying to fall back to excluding kernel samples", paranoid);
+ evsel->attr.exclude_kernel = 1;
+
return true;
}
"Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n"
"which controls use of the performance events system by\n"
"unprivileged users (without CAP_SYS_ADMIN).\n\n"
- "The default value is 1:\n\n"
+ "The current value is %d:\n\n"
" -1: Allow use of (almost) all events by all users\n"
">= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK\n"
">= 1: Disallow CPU event access by users without CAP_SYS_ADMIN\n"
">= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN",
- target->system_wide ? "system-wide " : "");
+ target->system_wide ? "system-wide " : "",
+ perf_event_paranoid());
case ENOENT:
return scnprintf(msg, size, "The %s event is not supported.",
perf_evsel__name(evsel));
#define PERF_EVENT_TYPE(config) __PERF_EVENT_FIELD(config, TYPE)
#define PERF_EVENT_ID(config) __PERF_EVENT_FIELD(config, EVENT)
-#define for_each_subsystem(sys_dir, sys_dirent, sys_next) \
- while (!readdir_r(sys_dir, &sys_dirent, &sys_next) && sys_next) \
- if (sys_dirent.d_type == DT_DIR && \
- (strcmp(sys_dirent.d_name, ".")) && \
- (strcmp(sys_dirent.d_name, "..")))
+#define for_each_subsystem(sys_dir, sys_dirent) \
+ while ((sys_dirent = readdir(sys_dir)) != NULL) \
+ if (sys_dirent->d_type == DT_DIR && \
+ (strcmp(sys_dirent->d_name, ".")) && \
+ (strcmp(sys_dirent->d_name, "..")))
static int tp_event_has_id(struct dirent *sys_dir, struct dirent *evt_dir)
{
return 0;
}
-#define for_each_event(sys_dirent, evt_dir, evt_dirent, evt_next) \
- while (!readdir_r(evt_dir, &evt_dirent, &evt_next) && evt_next) \
- if (evt_dirent.d_type == DT_DIR && \
- (strcmp(evt_dirent.d_name, ".")) && \
- (strcmp(evt_dirent.d_name, "..")) && \
- (!tp_event_has_id(&sys_dirent, &evt_dirent)))
+#define for_each_event(sys_dirent, evt_dir, evt_dirent) \
+ while ((evt_dirent = readdir(evt_dir)) != NULL) \
+ if (evt_dirent->d_type == DT_DIR && \
+ (strcmp(evt_dirent->d_name, ".")) && \
+ (strcmp(evt_dirent->d_name, "..")) && \
+ (!tp_event_has_id(sys_dirent, evt_dirent)))
#define MAX_EVENT_LENGTH 512
{
struct tracepoint_path *path = NULL;
DIR *sys_dir, *evt_dir;
- struct dirent *sys_next, *evt_next, sys_dirent, evt_dirent;
+ struct dirent *sys_dirent, *evt_dirent;
char id_buf[24];
int fd;
u64 id;
if (!sys_dir)
return NULL;
- for_each_subsystem(sys_dir, sys_dirent, sys_next) {
+ for_each_subsystem(sys_dir, sys_dirent) {
snprintf(dir_path, MAXPATHLEN, "%s/%s", tracing_events_path,
- sys_dirent.d_name);
+ sys_dirent->d_name);
evt_dir = opendir(dir_path);
if (!evt_dir)
continue;
- for_each_event(sys_dirent, evt_dir, evt_dirent, evt_next) {
+ for_each_event(sys_dirent, evt_dir, evt_dirent) {
snprintf(evt_path, MAXPATHLEN, "%s/%s/id", dir_path,
- evt_dirent.d_name);
+ evt_dirent->d_name);
fd = open(evt_path, O_RDONLY);
if (fd < 0)
continue;
free(path);
return NULL;
}
- strncpy(path->system, sys_dirent.d_name,
+ strncpy(path->system, sys_dirent->d_name,
MAX_EVENT_LENGTH);
- strncpy(path->name, evt_dirent.d_name,
+ strncpy(path->name, evt_dirent->d_name,
MAX_EVENT_LENGTH);
return path;
}
bool name_only)
{
DIR *sys_dir, *evt_dir;
- struct dirent *sys_next, *evt_next, sys_dirent, evt_dirent;
+ struct dirent *sys_dirent, *evt_dirent;
char evt_path[MAXPATHLEN];
char dir_path[MAXPATHLEN];
char **evt_list = NULL;
goto out_close_sys_dir;
}
- for_each_subsystem(sys_dir, sys_dirent, sys_next) {
+ for_each_subsystem(sys_dir, sys_dirent) {
if (subsys_glob != NULL &&
- !strglobmatch(sys_dirent.d_name, subsys_glob))
+ !strglobmatch(sys_dirent->d_name, subsys_glob))
continue;
snprintf(dir_path, MAXPATHLEN, "%s/%s", tracing_events_path,
- sys_dirent.d_name);
+ sys_dirent->d_name);
evt_dir = opendir(dir_path);
if (!evt_dir)
continue;
- for_each_event(sys_dirent, evt_dir, evt_dirent, evt_next) {
+ for_each_event(sys_dirent, evt_dir, evt_dirent) {
if (event_glob != NULL &&
- !strglobmatch(evt_dirent.d_name, event_glob))
+ !strglobmatch(evt_dirent->d_name, event_glob))
continue;
if (!evt_num_known) {
}
snprintf(evt_path, MAXPATHLEN, "%s:%s",
- sys_dirent.d_name, evt_dirent.d_name);
+ sys_dirent->d_name, evt_dirent->d_name);
evt_list[evt_i] = strdup(evt_path);
if (evt_list[evt_i] == NULL)
int is_valid_tracepoint(const char *event_string)
{
DIR *sys_dir, *evt_dir;
- struct dirent *sys_next, *evt_next, sys_dirent, evt_dirent;
+ struct dirent *sys_dirent, *evt_dirent;
char evt_path[MAXPATHLEN];
char dir_path[MAXPATHLEN];
if (!sys_dir)
return 0;
- for_each_subsystem(sys_dir, sys_dirent, sys_next) {
+ for_each_subsystem(sys_dir, sys_dirent) {
snprintf(dir_path, MAXPATHLEN, "%s/%s", tracing_events_path,
- sys_dirent.d_name);
+ sys_dirent->d_name);
evt_dir = opendir(dir_path);
if (!evt_dir)
continue;
- for_each_event(sys_dirent, evt_dir, evt_dirent, evt_next) {
+ for_each_event(sys_dirent, evt_dir, evt_dirent) {
snprintf(evt_path, MAXPATHLEN, "%s:%s",
- sys_dirent.d_name, evt_dirent.d_name);
+ sys_dirent->d_name, evt_dirent->d_name);
if (!strcmp(evt_path, event_string)) {
closedir(evt_dir);
closedir(sys_dir);
static char *setup_overhead(char *keys)
{
+ if (sort__mode == SORT_MODE__DIFF)
+ return keys;
+
keys = prefix_if_not_in("overhead", keys);
if (symbol_conf.cumulate_callchain)
DIR *proc;
int max_threads = 32, items, i;
char path[256];
- struct dirent dirent, *next, **namelist = NULL;
+ struct dirent *dirent, **namelist = NULL;
struct thread_map *threads = thread_map__alloc(max_threads);
if (threads == NULL)
threads->nr = 0;
atomic_set(&threads->refcnt, 1);
- while (!readdir_r(proc, &dirent, &next) && next) {
+ while ((dirent = readdir(proc)) != NULL) {
char *end;
bool grow = false;
struct stat st;
- pid_t pid = strtol(dirent.d_name, &end, 10);
+ pid_t pid = strtol(dirent->d_name, &end, 10);
if (*end) /* only interested in proper numerical dirents */
continue;
- snprintf(path, sizeof(path), "/proc/%s", dirent.d_name);
+ snprintf(path, sizeof(path), "/proc/%s", dirent->d_name);
if (stat(path, &st) != 0)
continue;
TARGETS += pstore
TARGETS += ptrace
TARGETS += seccomp
+TARGETS += sigaltstack
TARGETS += size
TARGETS += static_keys
TARGETS += sysctl
--- /dev/null
+#!/bin/bash
+#
+# Alternate sleeping and spinning on randomly selected CPUs. The purpose
+# of this script is to inflict random OS jitter on a concurrently running
+# test.
+#
+# Usage: jitter.sh me duration [ sleepmax [ spinmax ] ]
+#
+# me: Random-number-generator seed salt.
+# duration: Time to run in seconds.
+# sleepmax: Maximum microseconds to sleep, defaults to one second.
+# spinmax: Maximum microseconds to spin, defaults to one millisecond.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, you can access it online at
+# http://www.gnu.org/licenses/gpl-2.0.html.
+#
+# Copyright (C) IBM Corporation, 2016
+#
+# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+
+me=$(($1 * 1000))
+duration=$2
+sleepmax=${3-1000000}
+spinmax=${4-1000}
+
+n=1
+
+starttime=`awk 'BEGIN { print systime(); }' < /dev/null`
+
+while :
+do
+ # Check for done.
+ t=`awk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
+ if test "$t" -gt "$duration"
+ then
+ exit 0;
+ fi
+
+ # Set affinity to randomly selected CPU
+ cpus=`ls /sys/devices/system/cpu/*/online |
+ sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' |
+ grep -v '^0*$'`
+ cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
+ srand(n + me + systime());
+ ncpus = split(cpus, ca);
+ curcpu = ca[int(rand() * ncpus + 1)];
+ mask = lshift(1, curcpu);
+ if (mask + 0 <= 0)
+ mask = 1;
+ printf("%#x\n", mask);
+ }' < /dev/null`
+ n=$(($n+1))
+ if ! taskset -p $cpumask $$ > /dev/null 2>&1
+ then
+ echo taskset failure: '"taskset -p ' $cpumask $$ '"'
+ exit 1
+ fi
+
+ # Sleep a random duration
+ sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
+ srand(n + me + systime());
+ printf("%06d", int(rand() * sleepmax));
+ }' < /dev/null`
+ n=$(($n+1))
+ sleep .$sleeptime
+
+ # Spin a random duration
+ limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
+ srand(n + me + systime());
+ printf("%06d", int(rand() * spinmax));
+ }' < /dev/null`
+ n=$(($n+1))
+ for i in {1..$limit}
+ do
+ echo > /dev/null
+ done
+done
+
+exit 1
--- /dev/null
+#!/bin/bash
+#
+# Analyze a given results directory for rcuperf performance measurements,
+# looking for ftrace data. Exits with 0 if data was found, analyzed, and
+# printed. Intended to be invoked from kvm-recheck-rcuperf.sh after
+# argument checking.
+#
+# Usage: kvm-recheck-rcuperf-ftrace.sh resdir
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, you can access it online at
+# http://www.gnu.org/licenses/gpl-2.0.html.
+#
+# Copyright (C) IBM Corporation, 2016
+#
+# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+
+i="$1"
+. tools/testing/selftests/rcutorture/bin/functions.sh
+
+if test "`grep -c 'rcu_exp_grace_period.*start' < $i/console.log`" -lt 100
+then
+ exit 10
+fi
+
+sed -e 's/^\[[^]]*]//' < $i/console.log |
+grep 'us : rcu_exp_grace_period' |
+sed -e 's/us : / : /' |
+tr -d '\015' |
+awk '
+$8 == "start" {
+ if (starttask != "")
+ nlost++;
+ starttask = $1;
+ starttime = $3;
+ startseq = $7;
+}
+
+$8 == "end" {
+ if (starttask == $1 && startseq == $7) {
+ curgpdur = $3 - starttime;
+ gptimes[++n] = curgpdur;
+ gptaskcnt[starttask]++;
+ sum += curgpdur;
+ if (curgpdur > 1000)
+ print "Long GP " starttime "us to " $3 "us (" curgpdur "us)";
+ starttask = "";
+ } else {
+ # Lost a message or some such, reset.
+ starttask = "";
+ nlost++;
+ }
+}
+
+$8 == "done" {
+ piggybackcnt[$1]++;
+}
+
+END {
+ newNR = asort(gptimes);
+ if (newNR <= 0) {
+ print "No ftrace records found???"
+ exit 10;
+ }
+ pct50 = int(newNR * 50 / 100);
+ if (pct50 < 1)
+ pct50 = 1;
+ pct90 = int(newNR * 90 / 100);
+ if (pct90 < 1)
+ pct90 = 1;
+ pct99 = int(newNR * 99 / 100);
+ if (pct99 < 1)
+ pct99 = 1;
+ div = 10 ** int(log(gptimes[pct90]) / log(10) + .5) / 100;
+ print "Histogram bucket size: " div;
+ last = gptimes[1] - 10;
+ count = 0;
+ for (i = 1; i <= newNR; i++) {
+ current = div * int(gptimes[i] / div);
+ if (last == current) {
+ count++;
+ } else {
+ if (count > 0)
+ print last, count;
+ count = 1;
+ last = current;
+ }
+ }
+ if (count > 0)
+ print last, count;
+ print "Distribution of grace periods across tasks:";
+ for (i in gptaskcnt) {
+ print "\t" i, gptaskcnt[i];
+ nbatches += gptaskcnt[i];
+ }
+ ngps = nbatches;
+ print "Distribution of piggybacking across tasks:";
+ for (i in piggybackcnt) {
+ print "\t" i, piggybackcnt[i];
+ ngps += piggybackcnt[i];
+ }
+ print "Average grace-period duration: " sum / newNR " microseconds";
+ print "Minimum grace-period duration: " gptimes[1];
+ print "50th percentile grace-period duration: " gptimes[pct50];
+ print "90th percentile grace-period duration: " gptimes[pct90];
+ print "99th percentile grace-period duration: " gptimes[pct99];
+ print "Maximum grace-period duration: " gptimes[newNR];
+ print "Grace periods: " ngps + 0 " Batches: " nbatches + 0 " Ratio: " ngps / nbatches " Lost: " nlost + 0;
+ print "Computed from ftrace data.";
+}'
+exit 0
--- /dev/null
+#!/bin/bash
+#
+# Analyze a given results directory for rcuperf performance measurements.
+#
+# Usage: kvm-recheck-rcuperf.sh resdir
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, you can access it online at
+# http://www.gnu.org/licenses/gpl-2.0.html.
+#
+# Copyright (C) IBM Corporation, 2016
+#
+# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+
+i="$1"
+if test -d $i
+then
+ :
+else
+ echo Unreadable results directory: $i
+ exit 1
+fi
+PATH=`pwd`/tools/testing/selftests/rcutorture/bin:$PATH; export PATH
+. tools/testing/selftests/rcutorture/bin/functions.sh
+
+if kvm-recheck-rcuperf-ftrace.sh $i
+then
+ # ftrace data was successfully analyzed, call it good!
+ exit 0
+fi
+
+configfile=`echo $i | sed -e 's/^.*\///'`
+
+sed -e 's/^\[[^]]*]//' < $i/console.log |
+awk '
+/-perf: .* gps: .* batches:/ {
+ ngps = $9;
+ nbatches = $11;
+}
+
+/-perf: .*writer-duration/ {
+ gptimes[++n] = $5 / 1000.;
+ sum += $5 / 1000.;
+}
+
+END {
+ newNR = asort(gptimes);
+ if (newNR <= 0) {
+ print "No rcuperf records found???"
+ exit;
+ }
+ pct50 = int(newNR * 50 / 100);
+ if (pct50 < 1)
+ pct50 = 1;
+ pct90 = int(newNR * 90 / 100);
+ if (pct90 < 1)
+ pct90 = 1;
+ pct99 = int(newNR * 99 / 100);
+ if (pct99 < 1)
+ pct99 = 1;
+ div = 10 ** int(log(gptimes[pct90]) / log(10) + .5) / 100;
+ print "Histogram bucket size: " div;
+ last = gptimes[1] - 10;
+ count = 0;
+ for (i = 1; i <= newNR; i++) {
+ current = div * int(gptimes[i] / div);
+ if (last == current) {
+ count++;
+ } else {
+ if (count > 0)
+ print last, count;
+ count = 1;
+ last = current;
+ }
+ }
+ if (count > 0)
+ print last, count;
+ print "Average grace-period duration: " sum / newNR " microseconds";
+ print "Minimum grace-period duration: " gptimes[1];
+ print "50th percentile grace-period duration: " gptimes[pct50];
+ print "90th percentile grace-period duration: " gptimes[pct90];
+ print "99th percentile grace-period duration: " gptimes[pct99];
+ print "Maximum grace-period duration: " gptimes[newNR];
+ print "Grace periods: " ngps + 0 " Batches: " nbatches + 0 " Ratio: " ngps / nbatches;
+ print "Computed from rcuperf printk output.";
+}'
cat $i/Make.oldconfig.err
fi
parse-build.sh $i/Make.out $configfile
- parse-torture.sh $i/console.log $configfile
+ if test "$TORTURE_SUITE" != rcuperf
+ then
+ parse-torture.sh $i/console.log $configfile
+ fi
parse-console.sh $i/console.log $configfile
if test -r $i/Warnings
then
# Execute this in the source tree. Do not run it as a background task
# because qemu does not seem to like that much.
#
-# Usage: kvm-test-1-run.sh config builddir resdir minutes qemu-args boot_args
+# Usage: kvm-test-1-run.sh config builddir resdir seconds qemu-args boot_args
#
# qemu-args defaults to "-enable-kvm -soundhw pcspk -nographic", along with
# arguments specifying the number of CPUs and other
# CONFIG_PCMCIA=n
# CONFIG_CARDBUS=n
# CONFIG_YENTA=n
-if kvm-build.sh $config_template $builddir $T
+base_resdir=`echo $resdir | sed -e 's/\.[0-9]\+$//'`
+if test "$base_resdir" != "$resdir" -a -f $base_resdir/bzImage -a -f $base_resdir/vmlinux
then
+ # Rerunning previous test, so use that test's kernel.
+ QEMU="`identify_qemu $base_resdir/vmlinux`"
+ KERNEL=$base_resdir/bzImage
+ ln -s $base_resdir/Make*.out $resdir # for kvm-recheck.sh
+ ln -s $base_resdir/.config $resdir # for kvm-recheck.sh
+elif kvm-build.sh $config_template $builddir $T
+then
+ # Had to build a kernel for this test.
QEMU="`identify_qemu $builddir/vmlinux`"
BOOT_IMAGE="`identify_boot_image $QEMU`"
cp $builddir/Make*.out $resdir
+ cp $builddir/vmlinux $resdir
cp $builddir/.config $resdir
if test -n "$BOOT_IMAGE"
then
cp $builddir/$BOOT_IMAGE $resdir
+ KERNEL=$resdir/bzImage
else
echo No identifiable boot image, not running KVM, see $resdir.
echo Do the torture scripts know about your architecture?
fi
parse-build.sh $resdir/Make.out $title
- if test -f $builddir.wait
- then
- mv $builddir.wait $builddir.ready
- fi
else
+ # Build failed.
cp $builddir/Make*.out $resdir
cp $builddir/.config $resdir || :
echo Build failed, not running KVM, see $resdir.
fi
exit 1
fi
+if test -f $builddir.wait
+then
+ mv $builddir.wait $builddir.ready
+fi
while test -f $builddir.ready
do
sleep 1
done
-minutes=$4
-seconds=$(($minutes * 60))
+seconds=$4
qemu_args=$5
boot_args=$6
exit 0
fi
echo "NOTE: $QEMU either did not run or was interactive" > $resdir/console.log
-echo $QEMU $qemu_args -m 512 -kernel $resdir/bzImage -append \"$qemu_append $boot_args\" > $resdir/qemu-cmd
-( $QEMU $qemu_args -m 512 -kernel $resdir/bzImage -append "$qemu_append $boot_args"; echo $? > $resdir/qemu-retval ) &
-qemu_pid=$!
+echo $QEMU $qemu_args -m 512 -kernel $KERNEL -append \"$qemu_append $boot_args\" > $resdir/qemu-cmd
+( $QEMU $qemu_args -m 512 -kernel $KERNEL -append "$qemu_append $boot_args"& echo $! > $resdir/qemu_pid; wait `cat $resdir/qemu_pid`; echo $? > $resdir/qemu-retval ) &
commandcompleted=0
-echo Monitoring qemu job at pid $qemu_pid
+sleep 10 # Give qemu's pid a chance to reach the file
+if test -s "$resdir/qemu_pid"
+then
+ qemu_pid=`cat "$resdir/qemu_pid"`
+ echo Monitoring qemu job at pid $qemu_pid
+else
+ qemu_pid=""
+ echo Monitoring qemu job at yet-as-unknown pid
+fi
while :
do
+ if test -z "$qemu_pid" -a -s "$resdir/qemu_pid"
+ then
+ qemu_pid=`cat "$resdir/qemu_pid"`
+ fi
kruntime=`awk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
- if kill -0 $qemu_pid > /dev/null 2>&1
+ if test -z "$qemu_pid" || kill -0 "$qemu_pid" > /dev/null 2>&1
then
if test $kruntime -ge $seconds
then
ps -fp $killpid >> $resdir/Warnings 2>&1
fi
else
- echo ' ---' `date`: Kernel done
+ echo ' ---' `date`: "Kernel done"
fi
break
fi
done
-if test $commandcompleted -eq 0
+if test -z "$qemu_pid" -a -s "$resdir/qemu_pid"
+then
+ qemu_pid=`cat "$resdir/qemu_pid"`
+fi
+if test $commandcompleted -eq 0 -a -n "$qemu_pid"
then
echo Grace period for qemu job at pid $qemu_pid
while :
fi
sleep 1
done
+elif test -z "$qemu_pid"
+then
+ echo Unknown PID, cannot kill qemu command
fi
parse-torture.sh $resdir/console.log $title
trap 'rm -rf $T' 0
mkdir $T
-dur=30
+dur=$((30*60))
dryrun=""
KVM="`pwd`/tools/testing/selftests/rcutorture"; export KVM
PATH=${KVM}/bin:$PATH; export PATH
configs=""
cpus=0
ds=`date +%Y.%m.%d-%H:%M:%S`
+jitter=0
. functions.sh
echo " --dryrun sched|script"
echo " --duration minutes"
echo " --interactive"
+ echo " --jitter N [ maxsleep (us) [ maxspin (us) ] ]"
echo " --kmake-arg kernel-make-arguments"
echo " --mac nn:nn:nn:nn:nn:nn"
echo " --no-initrd"
;;
--duration)
checkarg --duration "(minutes)" $# "$2" '^[0-9]*$' '^error'
- dur=$2
+ dur=$(($2*60))
shift
;;
--interactive)
TORTURE_QEMU_INTERACTIVE=1; export TORTURE_QEMU_INTERACTIVE
;;
+ --jitter)
+ checkarg --jitter "(# threads [ sleep [ spin ] ])" $# "$2" '^-\{,1\}[0-9]\+\( \+[0-9]\+\)\{,2\} *$' '^error$'
+ jitter="$2"
+ shift
+ ;;
--kmake-arg)
checkarg --kmake-arg "(kernel make arguments)" $# "$2" '.*' '^error$'
TORTURE_KMAKE_ARG="$2"
shift
;;
--torture)
- checkarg --torture "(suite name)" "$#" "$2" '^\(lock\|rcu\)$' '^--'
+ checkarg --torture "(suite name)" "$#" "$2" '^\(lock\|rcu\|rcuperf\)$' '^--'
TORTURE_SUITE=$2
shift
;;
-v CONFIGDIR="$CONFIGFRAG/" \
-v KVM="$KVM" \
-v ncpus=$cpus \
+ -v jitter="$jitter" \
-v rd=$resdir/$ds/ \
-v dur=$dur \
-v TORTURE_QEMU_ARG="$TORTURE_QEMU_ARG" \
print "\techo ----", cfr[j], cpusr[j] ovf ": Starting kernel. `date` >> " rd "/log";
print "fi"
}
+ njitter = 0;
+ split(jitter, ja);
+ if (ja[1] == -1 && ncpus == 0)
+ njitter = 1;
+ else if (ja[1] == -1)
+ njitter = ncpus;
+ else
+ njitter = ja[1];
+ for (j = 0; j < njitter; j++)
+ print "jitter.sh " j " " dur " " ja[2] " " ja[3] "&"
print "wait"
print "if test -z \"$TORTURE_BUILDONLY\""
print "then"
CONFIG_SUSPEND=n
CONFIG_HIBERNATION=n
CONFIG_RCU_FANOUT=4
-CONFIG_RCU_FANOUT_LEAF=4
+CONFIG_RCU_FANOUT_LEAF=3
CONFIG_RCU_NOCB_CPU=n
CONFIG_DEBUG_LOCK_ALLOC=n
CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
-rcutorture.torture_type=rcu_bh
+rcutorture.torture_type=rcu_bh rcutree.rcu_fanout_leaf=4
--- /dev/null
+CONFIG_RCU_PERF_TEST=y
+CONFIG_PRINTK_TIME=y
--- /dev/null
+CONFIG_SMP=y
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
+#CHECK#CONFIG_PREEMPT_RCU=y
+CONFIG_HZ_PERIODIC=n
+CONFIG_NO_HZ_IDLE=y
+CONFIG_NO_HZ_FULL=n
+CONFIG_RCU_FAST_NO_HZ=n
+CONFIG_RCU_TRACE=n
+CONFIG_HOTPLUG_CPU=n
+CONFIG_SUSPEND=n
+CONFIG_HIBERNATION=n
+CONFIG_RCU_NOCB_CPU=n
+CONFIG_DEBUG_LOCK_ALLOC=n
+CONFIG_PROVE_LOCKING=n
+CONFIG_RCU_BOOST=n
+CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
+CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TRACE=y
--- /dev/null
+CONFIG_SMP=y
+CONFIG_NR_CPUS=54
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
+#CHECK#CONFIG_PREEMPT_RCU=y
+CONFIG_HZ_PERIODIC=n
+CONFIG_NO_HZ_IDLE=y
+CONFIG_NO_HZ_FULL=n
+CONFIG_RCU_FAST_NO_HZ=n
+CONFIG_RCU_TRACE=n
+CONFIG_HOTPLUG_CPU=n
+CONFIG_SUSPEND=n
+CONFIG_HIBERNATION=n
+CONFIG_RCU_FANOUT=3
+CONFIG_RCU_FANOUT_LEAF=2
+CONFIG_RCU_NOCB_CPU=n
+CONFIG_DEBUG_LOCK_ALLOC=n
+CONFIG_PROVE_LOCKING=n
+CONFIG_RCU_BOOST=n
+CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
+CONFIG_RCU_EXPERT=y
+CONFIG_RCU_TRACE=y
--- /dev/null
+#!/bin/bash
+#
+# Torture-suite-dependent shell functions for the rest of the scripts.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, you can access it online at
+# http://www.gnu.org/licenses/gpl-2.0.html.
+#
+# Copyright (C) IBM Corporation, 2015
+#
+# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+
+# rcuperf_param_nreaders bootparam-string
+#
+# Adds nreaders rcuperf module parameter if not already specified.
+rcuperf_param_nreaders () {
+ if ! echo "$1" | grep -q "rcuperf.nreaders"
+ then
+ echo rcuperf.nreaders=-1
+ fi
+}
+
+# rcuperf_param_nwriters bootparam-string
+#
+# Adds nwriters rcuperf module parameter if not already specified.
+rcuperf_param_nwriters () {
+ if ! echo "$1" | grep -q "rcuperf.nwriters"
+ then
+ echo rcuperf.nwriters=-1
+ fi
+}
+
+# per_version_boot_params bootparam-string config-file seconds
+#
+# Adds per-version torture-module parameters to kernels supporting them.
+per_version_boot_params () {
+ echo $1 `rcuperf_param_nreaders "$1"` \
+ `rcuperf_param_nwriters "$1"` \
+ rcuperf.perf_runnable=1 \
+ rcuperf.shutdown=1 \
+ rcuperf.verbose=1
+}
--- /dev/null
+CFLAGS = -Wall
+BINARIES = sas
+all: $(BINARIES)
+
+include ../lib.mk
+
+clean:
+ rm -rf $(BINARIES)
--- /dev/null
+/*
+ * Stas Sergeev <stsp@users.sourceforge.net>
+ *
+ * test sigaltstack(SS_ONSTACK | SS_AUTODISARM)
+ * If that succeeds, then swapcontext() can be used inside sighandler safely.
+ *
+ */
+
+#define _GNU_SOURCE
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <ucontext.h>
+#include <alloca.h>
+#include <string.h>
+#include <assert.h>
+#include <errno.h>
+
+#ifndef SS_AUTODISARM
+#define SS_AUTODISARM (1U << 31)
+#endif
+
+static void *sstack, *ustack;
+static ucontext_t uc, sc;
+static const char *msg = "[OK]\tStack preserved";
+static const char *msg2 = "[FAIL]\tStack corrupted";
+struct stk_data {
+ char msg[128];
+ int flag;
+};
+
+void my_usr1(int sig, siginfo_t *si, void *u)
+{
+ char *aa;
+ int err;
+ stack_t stk;
+ struct stk_data *p;
+
+ register unsigned long sp asm("sp");
+
+ if (sp < (unsigned long)sstack ||
+ sp >= (unsigned long)sstack + SIGSTKSZ) {
+ printf("[FAIL]\tSP is not on sigaltstack\n");
+ exit(EXIT_FAILURE);
+ }
+ /* put some data on stack. other sighandler will try to overwrite it */
+ aa = alloca(1024);
+ assert(aa);
+ p = (struct stk_data *)(aa + 512);
+ strcpy(p->msg, msg);
+ p->flag = 1;
+ printf("[RUN]\tsignal USR1\n");
+ err = sigaltstack(NULL, &stk);
+ if (err) {
+ perror("[FAIL]\tsigaltstack()");
+ exit(EXIT_FAILURE);
+ }
+ if (stk.ss_flags != SS_DISABLE)
+ printf("[FAIL]\tss_flags=%i, should be SS_DISABLE\n",
+ stk.ss_flags);
+ else
+ printf("[OK]\tsigaltstack is disabled in sighandler\n");
+ swapcontext(&sc, &uc);
+ printf("%s\n", p->msg);
+ if (!p->flag) {
+ printf("[RUN]\tAborting\n");
+ exit(EXIT_FAILURE);
+ }
+}
+
+void my_usr2(int sig, siginfo_t *si, void *u)
+{
+ char *aa;
+ struct stk_data *p;
+
+ printf("[RUN]\tsignal USR2\n");
+ aa = alloca(1024);
+ /* dont run valgrind on this */
+ /* try to find the data stored by previous sighandler */
+ p = memmem(aa, 1024, msg, strlen(msg));
+ if (p) {
+ printf("[FAIL]\tsigaltstack re-used\n");
+ /* corrupt the data */
+ strcpy(p->msg, msg2);
+ /* tell other sighandler that his data is corrupted */
+ p->flag = 0;
+ }
+}
+
+static void switch_fn(void)
+{
+ printf("[RUN]\tswitched to user ctx\n");
+ raise(SIGUSR2);
+ setcontext(&sc);
+}
+
+int main(void)
+{
+ struct sigaction act;
+ stack_t stk;
+ int err;
+
+ sigemptyset(&act.sa_mask);
+ act.sa_flags = SA_ONSTACK | SA_SIGINFO;
+ act.sa_sigaction = my_usr1;
+ sigaction(SIGUSR1, &act, NULL);
+ act.sa_sigaction = my_usr2;
+ sigaction(SIGUSR2, &act, NULL);
+ sstack = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
+ if (sstack == MAP_FAILED) {
+ perror("mmap()");
+ return EXIT_FAILURE;
+ }
+
+ err = sigaltstack(NULL, &stk);
+ if (err) {
+ perror("[FAIL]\tsigaltstack()");
+ exit(EXIT_FAILURE);
+ }
+ if (stk.ss_flags == SS_DISABLE) {
+ printf("[OK]\tInitial sigaltstack state was SS_DISABLE\n");
+ } else {
+ printf("[FAIL]\tInitial sigaltstack state was %i; should have been SS_DISABLE\n", stk.ss_flags);
+ return EXIT_FAILURE;
+ }
+
+ stk.ss_sp = sstack;
+ stk.ss_size = SIGSTKSZ;
+ stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
+ err = sigaltstack(&stk, NULL);
+ if (err) {
+ if (errno == EINVAL) {
+ printf("[NOTE]\tThe running kernel doesn't support SS_AUTODISARM\n");
+ /*
+ * If test cases for the !SS_AUTODISARM variant were
+ * added, we could still run them. We don't have any
+ * test cases like that yet, so just exit and report
+ * success.
+ */
+ return 0;
+ } else {
+ perror("[FAIL]\tsigaltstack(SS_ONSTACK | SS_AUTODISARM)");
+ return EXIT_FAILURE;
+ }
+ }
+
+ ustack = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
+ if (ustack == MAP_FAILED) {
+ perror("mmap()");
+ return EXIT_FAILURE;
+ }
+ getcontext(&uc);
+ uc.uc_link = NULL;
+ uc.uc_stack.ss_sp = ustack;
+ uc.uc_stack.ss_size = SIGSTKSZ;
+ makecontext(&uc, switch_fn, 0);
+ raise(SIGUSR1);
+
+ err = sigaltstack(NULL, &stk);
+ if (err) {
+ perror("[FAIL]\tsigaltstack()");
+ exit(EXIT_FAILURE);
+ }
+ if (stk.ss_flags != SS_AUTODISARM) {
+ printf("[FAIL]\tss_flags=%i, should be SS_AUTODISARM\n",
+ stk.ss_flags);
+ exit(EXIT_FAILURE);
+ }
+ printf("[OK]\tsigaltstack is still SS_AUTODISARM after signal\n");
+
+ printf("[OK]\tTest passed\n");
+ return 0;
+}
projects / linux-2.6-block.git / commitdiff
