- if (a_swap(&c->_c_block, 0))
- __wake(&c->_c_block, -1, 0);
+ pthread_mutex_t *m;
+
+ if (!c->_c_waiters) return 0;
+
+ a_inc(&c->_c_seq);
+
+ /* If cond var is process-shared, simply wake all waiters. */
+ if (c->_c_mutex == (void *)-1) {
+ __wake(&c->_c_seq, -1, 0);
+ return 0;
+ }
+
+ /* Block waiters from returning so we can use the mutex. */
+ while (a_swap(&c->_c_lock, 1))
+ __wait(&c->_c_lock, &c->_c_lockwait, 1, 1);
+ if (!c->_c_waiters)
+ goto out;
+ m = c->_c_mutex;
+
+ /* Move waiter count to the mutex */
+ a_fetch_add(&m->_m_waiters, c->_c_waiters2);
+ c->_c_waiters2 = 0;
+
+ /* Perform the futex requeue, waking one waiter unless we know
+ * that the calling thread holds the mutex. */
+ __syscall(SYS_futex, &c->_c_seq, FUTEX_REQUEUE,
+ !m->_m_type || (m->_m_lock&INT_MAX)!=pthread_self()->tid,
+ INT_MAX, &m->_m_lock);
+
+out:
+ a_store(&c->_c_lock, 0);
+ if (c->_c_lockwait) __wake(&c->_c_lock, 1, 0);
+