From: Ingo Molnar <mingo@kernel.org>
To: Waiman Long <longman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/5] locking/lockdep: Add a faster path in __lock_release()
Date: Tue, 2 Oct 2018 11:03:02 +0200 [thread overview]
Message-ID: <20181002090302.GA116695@gmail.com> (raw)
In-Reply-To: <1538157201-29173-4-git-send-email-longman@redhat.com>
* Waiman Long <longman@redhat.com> wrote:
> 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 add0468..ca002c0 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -3625,6 +3625,13 @@ static int __lock_downgrade(struct lockdep_map *lock, 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 @@ static int __lock_downgrade(struct lockdep_map *lock, 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;
Minor nit:
s/depth - 1/depth-1
for slightly better readability.
Thanks,
Ingo
next prev parent reply other threads:[~2018-10-02 9:03 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-28 17:53 [PATCH 0/5] locking/lockdep: Improve lockdep performance Waiman Long
2018-09-28 17:53 ` [PATCH 1/5] locking/lockdep: Remove add_chain_cache_classes() Waiman Long
2018-09-28 17:53 ` [PATCH 2/5] locking/lockdep: Eliminate redundant irqs check in __lock_acquire() Waiman Long
2018-10-02 9:06 ` Ingo Molnar
2018-09-28 17:53 ` [PATCH 3/5] locking/lockdep: Add a faster path in __lock_release() Waiman Long
2018-10-02 9:03 ` Ingo Molnar [this message]
2018-09-28 17:53 ` [PATCH 4/5] locking/lockdep: Make class->ops a percpu counter Waiman Long
2018-09-28 20:25 ` kbuild test robot
2018-09-28 20:31 ` Waiman Long
2018-09-28 20:42 ` kbuild test robot
2018-10-02 9:39 ` Peter Zijlstra
2018-10-02 9:55 ` Ingo Molnar
2018-10-02 14:10 ` Waiman Long
2018-10-02 14:28 ` Peter Zijlstra
2018-10-02 18:53 ` Ingo Molnar
2018-09-28 17:53 ` [PATCH 5/5] locking/lockdep: Call lock_release after releasing the lock Waiman Long
2018-10-02 9:08 ` Ingo Molnar
2018-10-02 9:06 ` [PATCH 0/5] locking/lockdep: Improve lockdep performance Ingo Molnar
2018-10-02 13:57 ` Waiman Long
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