fix lost signals in cond vars

[musl] / src / thread / pthread_cond_broadcast.c

diff --git a/src/thread/pthread_cond_broadcast.c b/src/thread/pthread_cond_broadcast.c
index bf6de04..9c6a462 100644 (file)
--- a/src/thread/pthread_cond_broadcast.c
+++ b/src/thread/pthread_cond_broadcast.c
@@ -22,8 +22,12 @@ int pthread_cond_broadcast(pthread_cond_t *c)
        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. */