Messages in this thread Patch in this message | | | From | Davidlohr Bueso <> | Subject | [PATCH 1/2] locking/rwbase: Optimize rwbase_read_trylock | Date | Sun, 19 Sep 2021 22:20:30 -0700 |
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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> --- kernel/locking/rwbase_rt.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c index 88191f6e252c..a9034784a5a0 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; @@ -183,7 +182,7 @@ 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); -- 2.26.2
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