locking/lockdep: Add a faster path in __lock_release() (ce52a18d) · Commits · 戴 / test

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 <longman@redhat.com> Acked-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Link: http://lkml.kernel.org/r/1538511560-10090-4-git-send-email-longman@redhat.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/locking/lockdep.c

+14 −3

Original line number	Diff line number	Diff line
		@@ -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)

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