Refine tx_mutex

Author: Cuda-Chen

virtio-snd.c

@@ -526,12 +526,9 @@ static void virtio_snd_read_pcm_prepare(const virtio_snd_pcm_hdr_t *query,
         return;
     }
 
-    /* Control the callback to prepare the buffer */
-    /* TODO: add lock to avoid race condition */
-    // pthread_mutex_lock(&virtio_snd_mutex);
     props->v.guest_playing = 0;
     props->v.stream_id = stream_id;
-    // pthread_mutex_unlock(&virtio_snd_mutex);
+
     props->pp.hdr.hdr.code = VIRTIO_SND_R_PCM_PREPARE;
     uint32_t period_bytes = props->pp.period_bytes;
     uint32_t channels = props->pp.channels;
@@ -1130,6 +1127,7 @@ static void virtio_queue_notify_handler(
 }
 
 /* TX thread context */
+/* Control the callback to prepare the buffer */
 static void *func(void *args)
 {
     virtio_snd_state_t *vsnd = (virtio_snd_state_t *) args;