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authorDavidlohr Bueso <dave@stgolabs.net>2021-09-19 22:20:30 -0700
committerPeter Zijlstra <peterz@infradead.org>2021-10-07 13:51:07 +0200
commitc78416d122243c92992a1d1063f17ddd0bc80e6c (patch)
tree91ddd15c967aec7d0f1631b65b9ca8a696feb570 /kernel/locking
parent3f48565beb7219bbe8332391fc4ca758054b00c5 (diff)
downloadlinux-c78416d122243c92992a1d1063f17ddd0bc80e6c.tar.bz2
locking/rwbase: Optimize rwbase_read_trylock
Instead of a full barrier around the Rmw insn, micro-optimize for weakly ordered archs such that we only provide the required ACQUIRE semantics when taking the read lock. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Waiman Long <longman@redhat.com> Link: https://lkml.kernel.org/r/20210920052031.54220-2-dave@stgolabs.net
Diffstat (limited to 'kernel/locking')
-rw-r--r--kernel/locking/rwbase_rt.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c
index 15c81100f0e2..6fd3162e4098 100644
--- a/kernel/locking/rwbase_rt.c
+++ b/kernel/locking/rwbase_rt.c
@@ -59,8 +59,7 @@ static __always_inline int rwbase_read_trylock(struct rwbase_rt *rwb)
* set.
*/
for (r = atomic_read(&rwb->readers); r < 0;) {
- /* Fully-ordered if cmpxchg() succeeds, provides ACQUIRE */
- if (likely(atomic_try_cmpxchg(&rwb->readers, &r, r + 1)))
+ if (likely(atomic_try_cmpxchg_acquire(&rwb->readers, &r, r + 1)))
return 1;
}
return 0;
@@ -187,7 +186,7 @@ static inline void __rwbase_write_unlock(struct rwbase_rt *rwb, int bias,
/*
* _release() is needed in case that reader is in fast path, pairing
- * with atomic_try_cmpxchg() in rwbase_read_trylock(), provides RELEASE
+ * with atomic_try_cmpxchg_acquire() in rwbase_read_trylock().
*/
(void)atomic_add_return_release(READER_BIAS - bias, &rwb->readers);
raw_spin_unlock_irqrestore(&rtm->wait_lock, flags);