+ return 0;
+ }
+
+ /* 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);
+ }
+
+ /* Perform the futex requeue, waking one waiter unless we know
+ * that the calling thread holds the mutex. */
+ __syscall(SYS_futex, &c->_c_block, FUTEX_REQUEUE,
+ !m->_m_type || (m->_m_lock&INT_MAX)!=pthread_self()->tid,
+ INT_MAX, &m->_m_lock);
+
+ unlock(c);