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Groups > linux.kernel > #1423234
| From | Davidlohr Bueso <dave@stgolabs.net> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier |
| Date | 2016-06-15 19:00 +0200 |
| Message-ID | <rKmkx-52w-7@gated-at.bofh.it> (permalink) |
| References | <rK5jH-2zl-5@gated-at.bofh.it> <rK5jH-2zl-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Tue, 14 Jun 2016, Waiman Long wrote:
>The osq_lock() and osq_unlock() function may not provide the necessary
>acquire and release barrier in some cases. This patch makes sure
>that the proper barriers are provided when osq_lock() is successful
>or when osq_unlock() is called.
>
>Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
>---
> kernel/locking/osq_lock.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
>index 05a3785..7dd4ee5 100644
>--- a/kernel/locking/osq_lock.c
>+++ b/kernel/locking/osq_lock.c
>@@ -115,7 +115,7 @@ bool osq_lock(struct optimistic_spin_queue *lock)
> * cmpxchg in an attempt to undo our queueing.
> */
>
>- while (!READ_ONCE(node->locked)) {
>+ while (!smp_load_acquire(&node->locked)) {
Hmm this being a polling path, that barrier can get pretty expensive and
last I checked it was unnecessary:
036cc30c6b6 (locking/osq: No need for load/acquire when acquire-polling)
Thanks,
Davidlohr
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[RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Waiman Long <Waiman.Long@hpe.com> - 2016-06-15 00:50 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Boqun Feng <boqun.feng@gmail.com> - 2016-06-15 10:10 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Peter Zijlstra <peterz@infradead.org> - 2016-06-15 19:20 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Boqun Feng <boqun.feng@gmail.com> - 2016-06-16 04:20 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Will Deacon <will.deacon@arm.com> - 2016-06-16 12:20 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Boqun Feng <boqun.feng@gmail.com> - 2016-06-17 02:50 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Will Deacon <will.deacon@arm.com> - 2016-06-17 17:50 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Boqun Feng <boqun.feng@gmail.com> - 2016-06-18 10:50 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Will Deacon <will.deacon@arm.com> - 2016-06-20 10:10 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Davidlohr Bueso <dave@stgolabs.net> - 2016-06-15 19:00 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Peter Zijlstra <peterz@infradead.org> - 2016-06-15 19:20 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Davidlohr Bueso <dave@stgolabs.net> - 2016-06-15 20:30 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Peter Zijlstra <peterz@infradead.org> - 2016-06-15 20:50 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Davidlohr Bueso <dave@stgolabs.net> - 2016-06-15 21:00 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Davidlohr Bueso <dave@stgolabs.net> - 2016-06-17 03:20 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Davidlohr Bueso <dave@stgolabs.net> - 2016-06-17 18:30 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Davidlohr Bueso <dave@stgolabs.net> - 2016-06-17 18:50 +0200
Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Peter Zijlstra <peterz@infradead.org> - 2016-06-16 00:00 +0200
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