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| author | Davidlohr Bueso <dave@stgolabs.net> | 2021-09-19 22:20:30 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-10-07 13:51:07 +0200 |
| commit | c78416d122243c92992a1d1063f17ddd0bc80e6c (patch) | |
| tree | 91ddd15c967aec7d0f1631b65b9ca8a696feb570 /kernel/locking | |
| parent | 3f48565beb7219bbe8332391fc4ca758054b00c5 (diff) | |
| download | lwn-c78416d122243c92992a1d1063f17ddd0bc80e6c.tar.gz lwn-c78416d122243c92992a1d1063f17ddd0bc80e6c.zip | |
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.c | 5 |
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); |