m = c->_c_mutex;
/* Move waiter count to the mutex */
- a_fetch_add(&m->_m_waiters, c->_c_waiters);
- a_store(&c->_c_waiters, 0);
+ for (;;) {
+ int w = c->_c_waiters2;
+ a_fetch_add(&m->_m_waiters, w);
+ if (a_cas(&c->_c_waiters2, 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. */