optimize cond waiter move using atomic swap instead of cas loop

diff --git a/src/thread/pthread_cond_broadcast.c b/src/thread/pthread_cond_broadcast.c
index 7e5ea91c507401525d4616fe0154b8fb01fe39b8..4fab9994ed399e28a8ba0a8b138e129dfc0ba5f9 100644 (file)
--- 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. */