container freezer: implement freezer cgroup subsystem
authorMatt Helsley <matthltc@us.ibm.com>
Sun, 19 Oct 2008 03:27:21 +0000 (20:27 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Mon, 20 Oct 2008 15:52:34 +0000 (08:52 -0700)
This patch implements a new freezer subsystem in the control groups
framework.  It provides a way to stop and resume execution of all tasks in
a cgroup by writing in the cgroup filesystem.

The freezer subsystem in the container filesystem defines a file named
freezer.state.  Writing "FROZEN" to the state file will freeze all tasks
in the cgroup.  Subsequently writing "RUNNING" will unfreeze the tasks in
the cgroup.  Reading will return the current state.

* Examples of usage :

   # mkdir /containers/freezer
   # mount -t cgroup -ofreezer freezer  /containers
   # mkdir /containers/0
   # echo $some_pid > /containers/0/tasks

to get status of the freezer subsystem :

   # cat /containers/0/freezer.state
   RUNNING

to freeze all tasks in the container :

   # echo FROZEN > /containers/0/freezer.state
   # cat /containers/0/freezer.state
   FREEZING
   # cat /containers/0/freezer.state
   FROZEN

to unfreeze all tasks in the container :

   # echo RUNNING > /containers/0/freezer.state
   # cat /containers/0/freezer.state
   RUNNING

This is the basic mechanism which should do the right thing for user space
task in a simple scenario.

It's important to note that freezing can be incomplete.  In that case we
return EBUSY.  This means that some tasks in the cgroup are busy doing
something that prevents us from completely freezing the cgroup at this
time.  After EBUSY, the cgroup will remain partially frozen -- reflected
by freezer.state reporting "FREEZING" when read.  The state will remain
"FREEZING" until one of these things happens:

1) Userspace cancels the freezing operation by writing "RUNNING" to
the freezer.state file
2) Userspace retries the freezing operation by writing "FROZEN" to
the freezer.state file (writing "FREEZING" is not legal
and returns EIO)
3) The tasks that blocked the cgroup from entering the "FROZEN"
state disappear from the cgroup's set of tasks.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: export thaw_process]
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Acked-by: Serge E. Hallyn <serue@us.ibm.com>
Tested-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
30 files changed:
arch/alpha/Kconfig
arch/arm/Kconfig
arch/avr32/Kconfig
arch/blackfin/Kconfig
arch/cris/Kconfig
arch/frv/Kconfig
arch/h8300/Kconfig
arch/ia64/Kconfig
arch/m32r/Kconfig
arch/m68k/Kconfig
arch/m68knommu/Kconfig
arch/mips/Kconfig
arch/mn10300/Kconfig
arch/parisc/Kconfig
arch/powerpc/Kconfig
arch/s390/Kconfig
arch/sh/Kconfig
arch/sparc/Kconfig
arch/sparc64/Kconfig
arch/um/Kconfig
arch/x86/Kconfig
arch/xtensa/Kconfig
include/linux/cgroup_subsys.h
include/linux/freezer.h
init/Kconfig
kernel/Kconfig.freezer [new file with mode: 0644]
kernel/Makefile
kernel/cgroup_freezer.c [new file with mode: 0644]
kernel/freezer.c
kernel/power/Kconfig

index a0f642b6a4b92b556e08c8c1d1e357979cd48322..6110197757a3f6283bf999519f1e7649fb96a867 100644 (file)
@@ -70,6 +70,7 @@ config AUTO_IRQ_AFFINITY
        default y
 
 source "init/Kconfig"
+source "kernel/Kconfig.freezer"
 
 
 menu "System setup"
index 4853f9df37bd22a037f122bd7d78a9a6600cc474..df39d20f7425ad9c41679a566ae212f924a222ff 100644 (file)
@@ -192,6 +192,8 @@ config VECTORS_BASE
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 menu "System Type"
 
 choice
index 7c239a916275b6b66b326e7fc93c6207bdbaf270..33a5b2969eb4addf24e36a59159d72488530dc0b 100644 (file)
@@ -72,6 +72,8 @@ config GENERIC_BUG
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 menu "System Type and features"
 
 source "kernel/time/Kconfig"
index 8102c79aaa94044369612ab3a8dc3bb6e33aa807..29e71ed6b8a7fb9c5e4b8381244a4c3d5b1d47db 100644 (file)
@@ -64,8 +64,11 @@ config HARDWARE_PM
        depends on OPROFILE
 
 source "init/Kconfig"
+
 source "kernel/Kconfig.preempt"
 
+source "kernel/Kconfig.freezer"
+
 menu "Blackfin Processor Options"
 
 comment "Processor and Board Settings"
index 9389d38f222f2f749497b106872278a7da5bdd0b..07335e719bf835d7ad5e88a6b844f07210b4b6ba 100644 (file)
@@ -62,6 +62,8 @@ config HZ
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 menu "General setup"
 
 source "fs/Kconfig.binfmt"
index a5aac1b075628b8a30004d52bb73d2e1ce7d978f..9d1552a9ee2c88ddb40bc7d70dea316f725d2843 100644 (file)
@@ -66,6 +66,8 @@ mainmenu "Fujitsu FR-V Kernel Configuration"
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 
 menu "Fujitsu FR-V system setup"
 
index c7966746fbfec582938b77a37baaed384d1b0ec2..bd1995403c67d0f9b37b34674a6c80ab7ee2a76b 100644 (file)
@@ -90,6 +90,8 @@ config HZ
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 source "arch/h8300/Kconfig.cpu"
 
 menu "Executable file formats"
index 3b7aa38254a8408b5564a260eb7a2ef30cf8d5f8..912c57db2d2180888ee9b366d7fae435c45c354d 100644 (file)
@@ -7,6 +7,8 @@ mainmenu "IA-64 Linux Kernel Configuration"
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 menu "Processor type and features"
 
 config IA64
index 00289c178f895a6ad62a7fb34603af08d52bc961..dbaed4a638153bc43c5fa4d6e138039bb5cca8df 100644 (file)
@@ -42,6 +42,8 @@ config HZ
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 
 menu "Processor type and features"
 
index 677c93a490f6f49501e4c7d2e375fd42bb4dabc5..836fb66f080dcbadeb5f6d96fba8f01679d85d02 100644 (file)
@@ -62,6 +62,8 @@ mainmenu "Linux/68k Kernel Configuration"
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 menu "Platform dependent setup"
 
 config EISA
index 0a8998315e5ed9fcdada66d87c5ee1127e35b9ac..76b66feb74df82d42b21a4b8ac67d6df0f498812 100644 (file)
@@ -75,6 +75,8 @@ config NO_IOPORT
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 menu "Processor type and features"
 
 choice
index b905744d79153be3d3170e9f81ce4e0805974d71..5f149b030c0f9fc7949793c6d8591d4bf0fd0450 100644 (file)
@@ -1885,6 +1885,8 @@ config PROBE_INITRD_HEADER
          add initrd or initramfs image to the kernel image.
          Otherwise, say N.
 
+source "kernel/Kconfig.freezer"
+
 menu "Bus options (PCI, PCMCIA, EISA, ISA, TC)"
 
 config HW_HAS_EISA
index dd557c9cf001be6226441b78cb84753f5e50cb15..9a9f433588792f5030796b2686193f4983c98ce9 100644 (file)
@@ -68,6 +68,8 @@ mainmenu "Matsushita MN10300/AM33 Kernel Configuration"
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 
 menu "Matsushita MN10300 system setup"
 
index 8313fccced5e1553f6f3d7ff484d897d2d20b812..2bd1f6ef5db0c6bd45269701b36b4713c0a6def3 100644 (file)
@@ -90,6 +90,8 @@ config ARCH_MAY_HAVE_PC_FDC
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 
 menu "Processor type and features"
 
index 380baa1780e9197b060ce1594aa098340d4da538..9391199d9e7731d166b45130fa322e27936b1da0 100644 (file)
@@ -230,6 +230,8 @@ config PPC_OF_PLATFORM_PCI
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 source "arch/powerpc/sysdev/Kconfig"
 source "arch/powerpc/platforms/Kconfig"
 
index bc581d8a7cd9c35995e6bb75ae1f17d101840de1..70b7645ce745aa03863360201183a832aec3f130 100644 (file)
@@ -78,6 +78,8 @@ config S390
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 menu "Base setup"
 
 comment "Processor type and features"
index 5131d50f851ac44f0a81709708023e2c6f00a5af..2ed5713b7540ab4985e3b1fda64b9365d5a1a2fe 100644 (file)
@@ -106,6 +106,8 @@ config IO_TRAPPED
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 menu "System type"
 
 #
index 97671dac12a649765e3b8fda6d22317963872749..e594559c8dbaa7658f56f079354e8ed25468fdcf 100644 (file)
@@ -37,6 +37,8 @@ config HZ
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 menu "General machine setup"
 
 config SMP
index 5446e2a499b13d36e3e50a529e85cd0e91ad5de4..035b15af90d8a668583001ef9610ab761d7b9478 100644 (file)
@@ -96,6 +96,7 @@ config GENERIC_HARDIRQS_NO__DO_IRQ
        def_bool y
 
 source "init/Kconfig"
+source "kernel/Kconfig.freezer"
 
 menu "Processor type and features"
 
index 6976812cfb184553bb93778bba38b2f3c01f922c..393bccfe1785108579dc6c18bab682f2e7984110 100644 (file)
@@ -229,6 +229,8 @@ endmenu
 
 source "init/Kconfig"
 
+source "kernel/Kconfig.freezer"
+
 source "drivers/block/Kconfig"
 
 source "arch/um/Kconfig.char"
index bd3c2c53873ecb4cd0b944e31996b746884d6cf0..49349ba77d80b81141deb6065510e54fc74eb077 100644 (file)
@@ -193,6 +193,7 @@ config X86_TRAMPOLINE
 config KTIME_SCALAR
        def_bool X86_32
 source "init/Kconfig"
+source "kernel/Kconfig.freezer"
 
 menu "Processor type and features"
 
index 02e417d3d8e95815713b1420146b069112da6b99..a213260b51e5b4d8d3d64d7aebc85d2b2f21eb74 100644 (file)
@@ -55,6 +55,7 @@ config HZ
        default 100
 
 source "init/Kconfig"
+source "kernel/Kconfig.freezer"
 
 menu "Processor type and features"
 
index e2877454ec82df3205c0251f9c9759db9334dedb..9c22396e8b50355e3058e93807f293112622079f 100644 (file)
@@ -48,3 +48,9 @@ SUBSYS(devices)
 #endif
 
 /* */
+
+#ifdef CONFIG_CGROUP_FREEZER
+SUBSYS(freezer)
+#endif
+
+/* */
index 17e3bb42dd3cc541373aba08191e3592bdc6f67d..8f225339eee9e49329b842803d89c2b4c90f9d38 100644 (file)
@@ -46,26 +46,11 @@ static inline bool should_send_signal(struct task_struct *p)
 
 /*
  * Wake up a frozen process
- *
- * task_lock() is taken to prevent the race with refrigerator() which may
- * occur if the freezing of tasks fails.  Namely, without the lock, if the
- * freezing of tasks failed, thaw_tasks() might have run before a task in
- * refrigerator() could call frozen_process(), in which case the task would be
- * frozen and no one would thaw it.
  */
-static inline int thaw_process(struct task_struct *p)
-{
-       task_lock(p);
-       if (frozen(p)) {
-               p->flags &= ~PF_FROZEN;
-               task_unlock(p);
-               wake_up_process(p);
-               return 1;
-       }
-       clear_freeze_flag(p);
-       task_unlock(p);
-       return 0;
-}
+extern int __thaw_process(struct task_struct *p);
+
+/* Takes and releases task alloc lock using task_lock() */
+extern int thaw_process(struct task_struct *p);
 
 extern void refrigerator(void);
 extern int freeze_processes(void);
@@ -83,6 +68,12 @@ static inline int try_to_freeze(void)
 extern bool freeze_task(struct task_struct *p, bool sig_only);
 extern void cancel_freezing(struct task_struct *p);
 
+#ifdef CONFIG_CGROUP_FREEZER
+extern int cgroup_frozen(struct task_struct *task);
+#else /* !CONFIG_CGROUP_FREEZER */
+static inline int cgroup_frozen(struct task_struct *task) { return 0; }
+#endif /* !CONFIG_CGROUP_FREEZER */
+
 /*
  * The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
  * calls wait_for_completion(&vfork) and reset right after it returns from this
index 5ceff3249a2d84cd23110b99fb3f8a076e8cf56c..8828ed0b2051f16df1d3a491419d3e868ac8d014 100644 (file)
@@ -299,6 +299,13 @@ config CGROUP_NS
           for instance virtual servers and checkpoint/restart
           jobs.
 
+config CGROUP_FREEZER
+        bool "control group freezer subsystem"
+        depends on CGROUPS
+        help
+          Provides a way to freeze and unfreeze all tasks in a
+         cgroup.
+
 config CGROUP_DEVICE
        bool "Device controller for cgroups"
        depends on CGROUPS && EXPERIMENTAL
diff --git a/kernel/Kconfig.freezer b/kernel/Kconfig.freezer
new file mode 100644 (file)
index 0000000..a3bb4cb
--- /dev/null
@@ -0,0 +1,2 @@
+config FREEZER
+       def_bool PM_SLEEP || CGROUP_FREEZER
index e8194d15d5f4cc1f3c7f4fb398cd4a93d3eccd9d..066550aa61c5018a32dff60fcd75e6ffdebbdedd 100644 (file)
@@ -56,6 +56,7 @@ obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
 obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CGROUPS) += cgroup.o
 obj-$(CONFIG_CGROUP_DEBUG) += cgroup_debug.o
+obj-$(CONFIG_CGROUP_FREEZER) += cgroup_freezer.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_CGROUP_NS) += ns_cgroup.o
 obj-$(CONFIG_UTS_NS) += utsname.o
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
new file mode 100644 (file)
index 0000000..b08722d
--- /dev/null
@@ -0,0 +1,366 @@
+/*
+ * cgroup_freezer.c -  control group freezer subsystem
+ *
+ * Copyright IBM Corporation, 2007
+ *
+ * Author : Cedric Le Goater <clg@fr.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#include <linux/module.h>
+#include <linux/cgroup.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/freezer.h>
+#include <linux/seq_file.h>
+
+enum freezer_state {
+       STATE_RUNNING = 0,
+       STATE_FREEZING,
+       STATE_FROZEN,
+};
+
+struct freezer {
+       struct cgroup_subsys_state css;
+       enum freezer_state state;
+       spinlock_t lock; /* protects _writes_ to state */
+};
+
+static inline struct freezer *cgroup_freezer(
+               struct cgroup *cgroup)
+{
+       return container_of(
+               cgroup_subsys_state(cgroup, freezer_subsys_id),
+               struct freezer, css);
+}
+
+static inline struct freezer *task_freezer(struct task_struct *task)
+{
+       return container_of(task_subsys_state(task, freezer_subsys_id),
+                           struct freezer, css);
+}
+
+int cgroup_frozen(struct task_struct *task)
+{
+       struct freezer *freezer;
+       enum freezer_state state;
+
+       task_lock(task);
+       freezer = task_freezer(task);
+       state = freezer->state;
+       task_unlock(task);
+
+       return state == STATE_FROZEN;
+}
+
+/*
+ * cgroups_write_string() limits the size of freezer state strings to
+ * CGROUP_LOCAL_BUFFER_SIZE
+ */
+static const char *freezer_state_strs[] = {
+       "RUNNING",
+       "FREEZING",
+       "FROZEN",
+};
+
+/*
+ * State diagram
+ * Transitions are caused by userspace writes to the freezer.state file.
+ * The values in parenthesis are state labels. The rest are edge labels.
+ *
+ * (RUNNING) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN)
+ *    ^ ^                     |                       |
+ *    | \_______RUNNING_______/                       |
+ *    \_____________________________RUNNING___________/
+ */
+
+struct cgroup_subsys freezer_subsys;
+
+/* Locks taken and their ordering
+ * ------------------------------
+ * css_set_lock
+ * cgroup_mutex (AKA cgroup_lock)
+ * task->alloc_lock (AKA task_lock)
+ * freezer->lock
+ * task->sighand->siglock
+ *
+ * cgroup code forces css_set_lock to be taken before task->alloc_lock
+ *
+ * freezer_create(), freezer_destroy():
+ * cgroup_mutex [ by cgroup core ]
+ *
+ * can_attach():
+ * cgroup_mutex
+ *
+ * cgroup_frozen():
+ * task->alloc_lock (to get task's cgroup)
+ *
+ * freezer_fork() (preserving fork() performance means can't take cgroup_mutex):
+ * task->alloc_lock (to get task's cgroup)
+ * freezer->lock
+ *  sighand->siglock (if the cgroup is freezing)
+ *
+ * freezer_read():
+ * cgroup_mutex
+ *  freezer->lock
+ *   read_lock css_set_lock (cgroup iterator start)
+ *
+ * freezer_write() (freeze):
+ * cgroup_mutex
+ *  freezer->lock
+ *   read_lock css_set_lock (cgroup iterator start)
+ *    sighand->siglock
+ *
+ * freezer_write() (unfreeze):
+ * cgroup_mutex
+ *  freezer->lock
+ *   read_lock css_set_lock (cgroup iterator start)
+ *    task->alloc_lock (to prevent races with freeze_task())
+ *     sighand->siglock
+ */
+static struct cgroup_subsys_state *freezer_create(struct cgroup_subsys *ss,
+                                                 struct cgroup *cgroup)
+{
+       struct freezer *freezer;
+
+       freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL);
+       if (!freezer)
+               return ERR_PTR(-ENOMEM);
+
+       spin_lock_init(&freezer->lock);
+       freezer->state = STATE_RUNNING;
+       return &freezer->css;
+}
+
+static void freezer_destroy(struct cgroup_subsys *ss,
+                           struct cgroup *cgroup)
+{
+       kfree(cgroup_freezer(cgroup));
+}
+
+
+static int freezer_can_attach(struct cgroup_subsys *ss,
+                             struct cgroup *new_cgroup,
+                             struct task_struct *task)
+{
+       struct freezer *freezer;
+       int retval = 0;
+
+       /*
+        * The call to cgroup_lock() in the freezer.state write method prevents
+        * a write to that file racing against an attach, and hence the
+        * can_attach() result will remain valid until the attach completes.
+        */
+       freezer = cgroup_freezer(new_cgroup);
+       if (freezer->state == STATE_FROZEN)
+               retval = -EBUSY;
+       return retval;
+}
+
+static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
+{
+       struct freezer *freezer;
+
+       task_lock(task);
+       freezer = task_freezer(task);
+       task_unlock(task);
+
+       BUG_ON(freezer->state == STATE_FROZEN);
+       spin_lock_irq(&freezer->lock);
+       /* Locking avoids race with FREEZING -> RUNNING transitions. */
+       if (freezer->state == STATE_FREEZING)
+               freeze_task(task, true);
+       spin_unlock_irq(&freezer->lock);
+}
+
+/*
+ * caller must hold freezer->lock
+ */
+static void check_if_frozen(struct cgroup *cgroup,
+                            struct freezer *freezer)
+{
+       struct cgroup_iter it;
+       struct task_struct *task;
+       unsigned int nfrozen = 0, ntotal = 0;
+
+       cgroup_iter_start(cgroup, &it);
+       while ((task = cgroup_iter_next(cgroup, &it))) {
+               ntotal++;
+               /*
+                * Task is frozen or will freeze immediately when next it gets
+                * woken
+                */
+               if (frozen(task) ||
+                   (task_is_stopped_or_traced(task) && freezing(task)))
+                       nfrozen++;
+       }
+
+       /*
+        * Transition to FROZEN when no new tasks can be added ensures
+        * that we never exist in the FROZEN state while there are unfrozen
+        * tasks.
+        */
+       if (nfrozen == ntotal)
+               freezer->state = STATE_FROZEN;
+       cgroup_iter_end(cgroup, &it);
+}
+
+static int freezer_read(struct cgroup *cgroup, struct cftype *cft,
+                       struct seq_file *m)
+{
+       struct freezer *freezer;
+       enum freezer_state state;
+
+       if (!cgroup_lock_live_group(cgroup))
+               return -ENODEV;
+
+       freezer = cgroup_freezer(cgroup);
+       spin_lock_irq(&freezer->lock);
+       state = freezer->state;
+       if (state == STATE_FREEZING) {
+               /* We change from FREEZING to FROZEN lazily if the cgroup was
+                * only partially frozen when we exitted write. */
+               check_if_frozen(cgroup, freezer);
+               state = freezer->state;
+       }
+       spin_unlock_irq(&freezer->lock);
+       cgroup_unlock();
+
+       seq_puts(m, freezer_state_strs[state]);
+       seq_putc(m, '\n');
+       return 0;
+}
+
+static int try_to_freeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
+{
+       struct cgroup_iter it;
+       struct task_struct *task;
+       unsigned int num_cant_freeze_now = 0;
+
+       freezer->state = STATE_FREEZING;
+       cgroup_iter_start(cgroup, &it);
+       while ((task = cgroup_iter_next(cgroup, &it))) {
+               if (!freeze_task(task, true))
+                       continue;
+               if (task_is_stopped_or_traced(task) && freezing(task))
+                       /*
+                        * The freeze flag is set so these tasks will
+                        * immediately go into the fridge upon waking.
+                        */
+                       continue;
+               if (!freezing(task) && !freezer_should_skip(task))
+                       num_cant_freeze_now++;
+       }
+       cgroup_iter_end(cgroup, &it);
+
+       return num_cant_freeze_now ? -EBUSY : 0;
+}
+
+static int unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
+{
+       struct cgroup_iter it;
+       struct task_struct *task;
+
+       cgroup_iter_start(cgroup, &it);
+       while ((task = cgroup_iter_next(cgroup, &it))) {
+               int do_wake;
+
+               task_lock(task);
+               do_wake = __thaw_process(task);
+               task_unlock(task);
+               if (do_wake)
+                       wake_up_process(task);
+       }
+       cgroup_iter_end(cgroup, &it);
+       freezer->state = STATE_RUNNING;
+
+       return 0;
+}
+
+static int freezer_change_state(struct cgroup *cgroup,
+                               enum freezer_state goal_state)
+{
+       struct freezer *freezer;
+       int retval = 0;
+
+       freezer = cgroup_freezer(cgroup);
+       spin_lock_irq(&freezer->lock);
+       check_if_frozen(cgroup, freezer); /* may update freezer->state */
+       if (goal_state == freezer->state)
+               goto out;
+       switch (freezer->state) {
+       case STATE_RUNNING:
+               retval = try_to_freeze_cgroup(cgroup, freezer);
+               break;
+       case STATE_FREEZING:
+               if (goal_state == STATE_FROZEN) {
+                       /* Userspace is retrying after
+                        * "/bin/echo FROZEN > freezer.state" returned -EBUSY */
+                       retval = try_to_freeze_cgroup(cgroup, freezer);
+                       break;
+               }
+               /* state == FREEZING and goal_state == RUNNING, so unfreeze */
+       case STATE_FROZEN:
+               retval = unfreeze_cgroup(cgroup, freezer);
+               break;
+       default:
+               break;
+       }
+out:
+       spin_unlock_irq(&freezer->lock);
+
+       return retval;
+}
+
+static int freezer_write(struct cgroup *cgroup,
+                        struct cftype *cft,
+                        const char *buffer)
+{
+       int retval;
+       enum freezer_state goal_state;
+
+       if (strcmp(buffer, freezer_state_strs[STATE_RUNNING]) == 0)
+               goal_state = STATE_RUNNING;
+       else if (strcmp(buffer, freezer_state_strs[STATE_FROZEN]) == 0)
+               goal_state = STATE_FROZEN;
+       else
+               return -EIO;
+
+       if (!cgroup_lock_live_group(cgroup))
+               return -ENODEV;
+       retval = freezer_change_state(cgroup, goal_state);
+       cgroup_unlock();
+       return retval;
+}
+
+static struct cftype files[] = {
+       {
+               .name = "state",
+               .read_seq_string = freezer_read,
+               .write_string = freezer_write,
+       },
+};
+
+static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup)
+{
+       return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
+}
+
+struct cgroup_subsys freezer_subsys = {
+       .name           = "freezer",
+       .create         = freezer_create,
+       .destroy        = freezer_destroy,
+       .populate       = freezer_populate,
+       .subsys_id      = freezer_subsys_id,
+       .can_attach     = freezer_can_attach,
+       .attach         = NULL,
+       .fork           = freezer_fork,
+       .exit           = NULL,
+};
index cb0931f893061bb5d2b04678ac925dcc498a2f15..ba6248b323ef7f64fb78aa1123c2940ffce3e64d 100644 (file)
@@ -120,3 +120,35 @@ void cancel_freezing(struct task_struct *p)
                spin_unlock_irqrestore(&p->sighand->siglock, flags);
        }
 }
+
+/*
+ * Wake up a frozen process
+ *
+ * task_lock() is needed to prevent the race with refrigerator() which may
+ * occur if the freezing of tasks fails.  Namely, without the lock, if the
+ * freezing of tasks failed, thaw_tasks() might have run before a task in
+ * refrigerator() could call frozen_process(), in which case the task would be
+ * frozen and no one would thaw it.
+ */
+int __thaw_process(struct task_struct *p)
+{
+       if (frozen(p)) {
+               p->flags &= ~PF_FROZEN;
+               return 1;
+       }
+       clear_freeze_flag(p);
+       return 0;
+}
+
+int thaw_process(struct task_struct *p)
+{
+       task_lock(p);
+       if (__thaw_process(p) == 1) {
+               task_unlock(p);
+               wake_up_process(p);
+               return 1;
+       }
+       task_unlock(p);
+       return 0;
+}
+EXPORT_SYMBOL(thaw_process);
index ebdd7f55273dc1fe77fd068650484651d7a5dddb..dcd165f92a887881eefaf9f67bf6c612a4a94547 100644 (file)
@@ -85,9 +85,6 @@ config PM_SLEEP
        depends on SUSPEND || HIBERNATION || XEN_SAVE_RESTORE
        default y
 
-config FREEZER
-       def_bool PM_SLEEP
-
 config SUSPEND
        bool "Suspend to RAM and standby"
        depends on PM && ARCH_SUSPEND_POSSIBLE