lkml.org 
[lkml]   [2021]   [Sep]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 1/2] locking/rwbase: Optimize rwbase_read_trylock
Date
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
\
 
 \ /
  Last update: 2021-09-20 07:21    [W:1.335 / U:0.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site