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optimize cond waiter move using atomic swap instead of cas loop

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This commit is contained in:
Rich Felker
2011-09-25 21:10:50 -04:00
parent 09ec0f3aab
commit cf940165d4
1 changed files with 2 additions and 6 deletions
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src/thread/pthread_cond_broadcast.c
+1 -5
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@@ -30,12 +30,8 @@ int pthread_cond_broadcast(pthread_cond_t *c)
} }
/* Move waiter count to the mutex */ /* Move waiter count to the mutex */
for (;;) { w = a_swap(&c->_c_waiters, 0);
w = c->_c_waiters;
a_fetch_add(&m->_m_waiters, w); a_fetch_add(&m->_m_waiters, w);
if (a_cas(&c->_c_waiters, w, 0) == w) break;
a_fetch_add(&m->_m_waiters, -w);
}
/* Perform the futex requeue, waking one waiter unless we know /* Perform the futex requeue, waking one waiter unless we know
* that the calling thread holds the mutex. */ * that the calling thread holds the mutex. */