locking/lockdep: Provide enum lock_usage_bit mask names

It makes the code more self-explanatory and tells throughout the code
what magic number refers to:

 - state (Hardirq/Softirq)
 - direction (used in or enabled above state)
 - read or write

We can even remove some comments that were compensating for the lack of
those constant names.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/1545973321-24422-3-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 1dcd8341e35b4cc7d0425650e32592dcf7d6d875..608f74ed8bb9016a1d8670f6fffee1bcfa1a173f 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1624,29 +1624,18 @@ static const char *state_rnames[] = {
 
 static inline const char *state_name(enum lock_usage_bit bit)
 {
-       return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
+       return (bit & LOCK_USAGE_READ_MASK) ? state_rnames[bit >> 2] : state_names[bit >> 2];
 }
 
 static int exclusive_bit(int new_bit)
 {
-       /*
-        * USED_IN
-        * USED_IN_READ
-        * ENABLED
-        * ENABLED_READ
-        *
-        * bit 0 - write/read
-        * bit 1 - used_in/enabled
-        * bit 2+  state
-        */
-
-       int state = new_bit & ~3;
-       int dir = new_bit & 2;
+       int state = new_bit & LOCK_USAGE_STATE_MASK;
+       int dir = new_bit & LOCK_USAGE_DIR_MASK;
 
        /*
         * keep state, bit flip the direction and strip read.
         */
-       return state | (dir ^ 2);
+       return state | (dir ^ LOCK_USAGE_DIR_MASK);
 }
 
 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
@@ -2662,8 +2651,8 @@ mark_lock_irq(struct task_struct *curr, struct held_lock *this,
                enum lock_usage_bit new_bit)
 {
        int excl_bit = exclusive_bit(new_bit);
-       int read = new_bit & 1;
-       int dir = new_bit & 2;
+       int read = new_bit & LOCK_USAGE_READ_MASK;
+       int dir = new_bit & LOCK_USAGE_DIR_MASK;
 
        /*
         * mark USED_IN has to look forwards -- to ensure no dependency
@@ -2687,19 +2676,19 @@ mark_lock_irq(struct task_struct *curr, struct held_lock *this,
         * states.
         */
        if ((!read || !dir || STRICT_READ_CHECKS) &&
-                       !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
+                       !usage(curr, this, excl_bit, state_name(new_bit & ~LOCK_USAGE_READ_MASK)))
                return 0;
 
        /*
         * Check for read in write conflicts
         */
        if (!read) {
-               if (!valid_state(curr, this, new_bit, excl_bit + 1))
+               if (!valid_state(curr, this, new_bit, excl_bit + LOCK_USAGE_READ_MASK))
                        return 0;
 
                if (STRICT_READ_CHECKS &&
-                       !usage(curr, this, excl_bit + 1,
-                               state_name(new_bit + 1)))
+                       !usage(curr, this, excl_bit + LOCK_USAGE_READ_MASK,
+                               state_name(new_bit + LOCK_USAGE_READ_MASK)))
                        return 0;
        }
 
@@ -2723,7 +2712,7 @@ mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
                hlock = curr->held_locks + i;
 
                if (hlock->read)
-                       hlock_bit += 1; /* READ */
+                       hlock_bit += LOCK_USAGE_READ_MASK;
 
                BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
 

diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index 88c847a41c8ae78ea8fdfc75476b85c259466200..2ebb9d0ea91c57a624fa0bf78c51db29407ae36e 100644 (file)
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -22,6 +22,10 @@ enum lock_usage_bit {
        LOCK_USAGE_STATES
 };
 
+#define LOCK_USAGE_READ_MASK 1
+#define LOCK_USAGE_DIR_MASK  2
+#define LOCK_USAGE_STATE_MASK (~(LOCK_USAGE_READ_MASK | LOCK_USAGE_DIR_MASK))
+
 /*
  * Usage-state bitmasks:
  */