Use CV to block the TX thread

Author: Cuda-Chen

virtio-snd.c

@@ -870,18 +870,20 @@ static void virtio_queue_notify_handler(
 static void *func(void *args)
 {
     virtio_snd_state_t *vsnd = (virtio_snd_state_t *) args;
-    fprintf(stderr, "*** tx desc handler is called ***\n");
-    pthread_mutex_lock(&virtio_snd_mutex);
-    while (tx_ev_notify <= 0) {
-        pthread_cond_wait(&virtio_snd_tx_cond, &virtio_snd_mutex);
-        fprintf(stderr, "wait for cond\n");
+    for (;;) {
+        fprintf(stderr, "*** tx desc handler is called ***\n");
+        pthread_mutex_lock(&virtio_snd_mutex);
+        while (tx_ev_notify <= 0) {
+            pthread_cond_wait(&virtio_snd_tx_cond, &virtio_snd_mutex);
+            fprintf(stderr, "wait for cond\n");
+        }
+        fprintf(stderr, "*** start tx critical section ***\n");
+        tx_ev_notify--;
+        fprintf(stderr, "*** tx desc handler ***\n");
+        virtio_queue_notify_handler(vsnd, 2, virtio_snd_tx_desc_handler);
+        fprintf(stderr, "*** end tx cirtical section ***\n");
+        pthread_mutex_unlock(&virtio_snd_mutex);
     }
-    fprintf(stderr, "*** start tx critical section ***\n");
-    tx_ev_notify--;
-    fprintf(stderr, "*** tx desc handler ***\n");
-    virtio_queue_notify_handler(vsnd, 2, virtio_snd_tx_desc_handler);
-    fprintf(stderr, "*** end tx cirtical section ***\n");
-    pthread_mutex_unlock(&virtio_snd_mutex);
     return NULL;
 }