synchronize cond var destruction with exiting waits

src/internal/pthread_impl.h

@@ -71,6 +71,7 @@ struct __timer {
 #define _c_lock __u.__i[5]
 #define _c_lockwait __u.__i[6]
 #define _c_waiters2 __u.__i[7]
+#define _c_destroy __u.__i[8]
 #define _rw_lock __u.__i[0]
 #define _rw_waiters __u.__i[1]
 #define _b_lock __u.__i[0]

src/thread/pthread_cond_destroy.c

@@ -2,5 +2,12 @@
 
 int pthread_cond_destroy(pthread_cond_t *c)
 {
+	int priv = c->_c_mutex != (void *)-1;
+	int cnt;
+	c->_c_destroy = 1;
+	if (c->_c_waiters)
+		__wake(&c->_c_seq, -1, priv);
+	while ((cnt = c->_c_waiters))
+		__wait(&c->_c_waiters, 0, cnt, priv);
 	return 0;
 }

src/thread/pthread_cond_timedwait.c

@@ -12,6 +12,7 @@ static void unwait(pthread_cond_t *c, pthread_mutex_t *m)
 
 	if (c->_c_mutex == (void *)-1) {
 		a_dec(&c->_c_waiters);
+		if (c->_c_destroy) __wake(&c->_c_waiters, 1, 0);
 		return;
 	}
 
@@ -23,6 +24,9 @@ static void unwait(pthread_cond_t *c, pthread_mutex_t *m)
 
 	a_store(&c->_c_lock, 0);
 	if (c->_c_lockwait) __wake(&c->_c_lock, 1, 1);
+
+	a_dec(&c->_c_waiters);
+	if (c->_c_destroy) __wake(&c->_c_waiters, 1, 1);
 }
 
 static void cleanup(void *p)