new futex-requeue-based pthread_cond_broadcast implementation

[musl] / src / thread / pthread_cond_timedwait.c

diff --git a/src/thread/pthread_cond_timedwait.c b/src/thread/pthread_cond_timedwait.c
index c71edc9..9616dd8 100644 (file)
--- a/src/thread/pthread_cond_timedwait.c
+++ b/src/thread/pthread_cond_timedwait.c
@@ -5,10 +5,25 @@ struct cm {
        pthread_mutex_t *m;
 };
 
+static void unwait(pthread_cond_t *c, pthread_mutex_t *m)
+{
+       int w;
+
+       /* Cannot leave waiting status if there are any live broadcasters
+        * which might be inspecting/using the mutex. */
+       while ((w=c->_c_bcast)) __wait(&c->_c_bcast, &c->_c_leavers, w, 0);
+
+       /* If the waiter count is zero, it must be the case that the
+        * caller's count has been moved to the mutex due to bcast. */
+       do w = c->_c_waiters;
+       while (w && a_cas(&c->_c_waiters, w, w-1)!=w);
+       if (!w) a_dec(&m->_m_waiters);
+}
+
 static void cleanup(void *p)
 {
        struct cm *cm = p;
-       a_dec(&cm->c->_c_waiters);
+       unwait(cm->c, cm->m);
        pthread_mutex_lock(cm->m);
 }
 
@@ -22,6 +37,8 @@ int pthread_cond_timedwait(pthread_cond_t *c, pthread_mutex_t *m, const struct t
 
        pthread_testcancel();
 
+       if (c->_c_mutex != (void *)-1) c->_c_mutex = m;
+
        a_inc(&c->_c_waiters);
        c->_c_block = tid = pthread_self()->tid;
 
@@ -31,7 +48,7 @@ int pthread_cond_timedwait(pthread_cond_t *c, pthread_mutex_t *m, const struct t
        while (c->_c_block == tid && (!e || e==EINTR));
        if (e == EINTR) e = 0;
 
-       a_dec(&c->_c_waiters);
+       unwait(c, m);
 
        if ((r=pthread_mutex_lock(m))) return r;