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authorWaiman Long <[email protected]>2018-10-02 16:19:18 -0400
committerIngo Molnar <[email protected]>2018-10-03 08:46:03 +0200
commitce52a18db45842f5b992851a552bd7f6acb2241b (patch)
treed4a2faed3b80b59485c8621bec27ed43432d7475
parent8ee10862476ef8b9e81e5b521205fd5c620b4ffb (diff)
locking/lockdep: Add a faster path in __lock_release()
When __lock_release() is called, the most likely unlock scenario is on the innermost lock in the chain. In this case, we can skip some of the checks and provide a faster path to completion. Signed-off-by: Waiman Long <[email protected]> Acked-by: Peter Zijlstra <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Will Deacon <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
-rw-r--r--kernel/locking/lockdep.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index a5d7db558928..511d30f88bce 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3626,6 +3626,13 @@ __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
curr->lockdep_depth = i;
curr->curr_chain_key = hlock->prev_chain_key;
+ /*
+ * The most likely case is when the unlock is on the innermost
+ * lock. In this case, we are done!
+ */
+ if (i == depth-1)
+ return 1;
+
if (reacquire_held_locks(curr, depth, i + 1))
return 0;
@@ -3633,10 +3640,14 @@ __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
* We had N bottles of beer on the wall, we drank one, but now
* there's not N-1 bottles of beer left on the wall...
*/
- if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
- return 0;
+ DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth-1);
- return 1;
+ /*
+ * Since reacquire_held_locks() would have called check_chain_key()
+ * indirectly via __lock_acquire(), we don't need to do it again
+ * on return.
+ */
+ return 0;
}
static int __lock_is_held(const struct lockdep_map *lock, int read)