From cf940165d4caf132405a3fe3df58b57eb735ac04 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sun, 25 Sep 2011 21:10:50 -0400
Subject: optimize cond waiter move using atomic swap instead of cas loop
---
src/thread/pthread_cond_broadcast.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
(limited to 'src')
diff --git a/src/thread/pthread_cond_broadcast.c b/src/thread/pthread_cond_broadcast.c
index 7e5ea91c..4fab9994 100644
--- a/src/thread/pthread_cond_broadcast.c
+++ b/src/thread/pthread_cond_broadcast.c
@@ -30,12 +30,8 @@ int pthread_cond_broadcast(pthread_cond_t *c)
}
/* Move waiter count to the mutex */
- for (;;) {
- w = c->_c_waiters;
- a_fetch_add(&m->_m_waiters, w);
- if (a_cas(&c->_c_waiters, w, 0) == w) break;
- a_fetch_add(&m->_m_waiters, -w);
- }
+ w = a_swap(&c->_c_waiters, 0);
+ a_fetch_add(&m->_m_waiters, w);
/* Perform the futex requeue, waking one waiter unless we know
* that the calling thread holds the mutex. */
--
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