fix lost signals in cond vars

[musl] / src / thread / pthread_cond_timedwait.c

diff --git a/src/thread/pthread_cond_timedwait.c b/src/thread/pthread_cond_timedwait.c
index e9b5e2f..e3dc814 100644 (file)
--- a/src/thread/pthread_cond_timedwait.c
+++ b/src/thread/pthread_cond_timedwait.c
@@ -7,6 +7,8 @@ struct cm {
 
 static void unwait(pthread_cond_t *c, pthread_mutex_t *m)
 {
+       int w;
+
        /* Removing a waiter is non-trivial if we could be using requeue
         * based broadcast signals, due to mutex access issues, etc. */
 
@@ -18,8 +20,10 @@ static void unwait(pthread_cond_t *c, pthread_mutex_t *m)
        while (a_swap(&c->_c_lock, 1))
                __wait(&c->_c_lock, &c->_c_lockwait, 1, 1);
 
-       if (c->_c_waiters) c->_c_waiters--;
-       else a_dec(&m->_m_waiters);
+       /* Atomically decrement waiters2 if positive, else mutex waiters. */
+       do w = c->_c_waiters2;
+       while (w && a_cas(&c->_c_waiters2, w, w-1)!=w);
+       if (!w) a_dec(&m->_m_waiters);
 
        a_store(&c->_c_lock, 0);
        if (c->_c_lockwait) __wake(&c->_c_lock, 1, 1);
@@ -42,16 +46,10 @@ int pthread_cond_timedwait(pthread_cond_t *c, pthread_mutex_t *m, const struct t
 
        pthread_testcancel();
 
-       if (c->_c_mutex == (void *)-1) {
-               a_inc(&c->_c_waiters);
-       } else {
-               c->_c_mutex = m;
-               while (a_swap(&c->_c_lock, 1))
-                       __wait(&c->_c_lock, &c->_c_lockwait, 1, 1);
-               c->_c_waiters++;
-               a_store(&c->_c_lock, 0);
-               if (c->_c_lockwait) __wake(&c->_c_lock, 1, 1);
-       }
+       if (c->_c_mutex != (void *)-1) c->_c_mutex = m;
+
+       a_inc(&c->_c_waiters);
+       a_inc(&c->_c_waiters2);
 
        seq = c->_c_seq;