From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>
Cc: linux-kernel@vger.kernel.org, Waiman Long <longman@redhat.com>
Subject: [PATCH v2 3/5] locking/lockdep: Add a faster path in __lock_release()
Date: Tue, 2 Oct 2018 16:19:18 -0400 [thread overview]
Message-ID: <1538511560-10090-4-git-send-email-longman@redhat.com> (raw)
In-Reply-To: <1538511560-10090-1-git-send-email-longman@redhat.com>
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>
---
kernel/locking/lockdep.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index bd59163b0550..b7774ff2516f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3625,6 +3625,13 @@ __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;
@@ -3632,10 +3639,14 @@ __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)
--
2.18.0
next prev parent reply other threads:[~2018-10-02 20:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-02 20:19 [PATCH v2 0/5] locking/lockdep: Improve lockdep performance Waiman Long
2018-10-02 20:19 ` [PATCH v2 1/5] locking/lockdep: Remove add_chain_cache_classes() Waiman Long
2018-10-03 7:30 ` [tip:locking/core] " tip-bot for Waiman Long
2018-10-02 20:19 ` [PATCH v2 2/5] locking/lockdep: Eliminate redundant irqs check in __lock_acquire() Waiman Long
2018-10-03 7:31 ` [tip:locking/core] locking/lockdep: Eliminate redundant IRQs " tip-bot for Waiman Long
2018-10-02 20:19 ` Waiman Long [this message]
2018-10-03 7:31 ` [tip:locking/core] locking/lockdep: Add a faster path in __lock_release() tip-bot for Waiman Long
2018-10-02 20:19 ` [PATCH v2 4/5] locking/lockdep: Make class->ops a percpu counter Waiman Long
2018-10-03 7:48 ` Peter Zijlstra
2018-10-03 7:54 ` Ingo Molnar
2018-10-03 8:24 ` Peter Zijlstra
2018-10-03 13:57 ` Waiman Long
2018-10-03 17:07 ` Waiman Long
2018-10-04 10:14 ` Ingo Molnar
2018-10-04 13:05 ` Waiman Long
2018-10-09 10:54 ` [tip:locking/core] locking/lockdep: Make class->ops a percpu counter and move it under CONFIG_DEBUG_LOCKDEP=y tip-bot for Waiman Long
2018-10-02 20:19 ` [PATCH v2 5/5] locking/lockdep: Call lock_release() after releasing the lock Waiman Long
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