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Subject[PATCH 5/5] locking/mcs: Use acquire/release semantics
Date
As such, weakly ordered archs can benefit from more relaxed use
of barriers when locking/unlocking.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
kernel/locking/mcs_spinlock.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/mcs_spinlock.h b/kernel/locking/mcs_spinlock.h
index fd91aaa..5b9102a 100644
--- a/kernel/locking/mcs_spinlock.h
+++ b/kernel/locking/mcs_spinlock.h
@@ -67,7 +67,7 @@ void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
node->locked = 0;
node->next = NULL;

- prev = xchg(lock, node);
+ prev = xchg_acquire(lock, node);
if (likely(prev == NULL)) {
/*
* Lock acquired, don't need to set node->locked to 1. Threads
@@ -98,7 +98,7 @@ void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
/*
* Release the lock by setting it to NULL
*/
- if (likely(cmpxchg(lock, node, NULL) == node))
+ if (likely(cmpxchg_release(lock, node, NULL) == node))
return;
/* Wait until the next pointer is set */
while (!(next = READ_ONCE(node->next)))
--
2.1.4


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