ALSA: compress: use mutex in drain

Since we dont have lock over the function, we need to acquire mutex
when checking and modifying states in drain and partial_drain handlers

Change-Id: I3f8af90a226b772492fb6e09c625ebedc8ebfeb5
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Eric Laurent <elaurent@google.com>
Signed-off-by: Krishnankutty Kolathappilly <kkolat@codeaurora.org>
diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index 4e7eff0..909c7c5 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -637,18 +637,29 @@
 	return retval;
 }
 
+/* this fn is called without lock being held and we change stream states here
+ * so while using the stream state auquire the lock but relase before invoking
+ * DSP as the call will possibly take a while
+ */
 static int snd_compr_drain(struct snd_compr_stream *stream)
 {
 	int retval;
 
+	mutex_lock(&stream->device->lock);
 	if (stream->runtime->state == SNDRV_PCM_STATE_PREPARED ||
-			stream->runtime->state == SNDRV_PCM_STATE_SETUP)
-		return -EPERM;
+			stream->runtime->state == SNDRV_PCM_STATE_SETUP) {
+		retval = -EPERM;
+		goto ret;
+	}
+	mutex_unlock(&stream->device->lock);
 	retval = stream->ops->trigger(stream, SND_COMPR_TRIGGER_DRAIN);
+	mutex_lock(&stream->device->lock);
 	if (!retval) {
 		stream->runtime->state = SNDRV_PCM_STATE_DRAINING;
 		wake_up(&stream->runtime->sleep);
 	}
+ret:
+	mutex_unlock(&stream->device->lock);
 	return retval;
 }
 
@@ -677,9 +688,14 @@
 static int snd_compr_partial_drain(struct snd_compr_stream *stream)
 {
 	int retval;
+
+	mutex_lock(&stream->device->lock);
 	if (stream->runtime->state == SNDRV_PCM_STATE_PREPARED ||
-			stream->runtime->state == SNDRV_PCM_STATE_SETUP)
+			stream->runtime->state == SNDRV_PCM_STATE_SETUP) {
+		mutex_unlock(&stream->device->lock);
 		return -EPERM;
+	}
+	mutex_unlock(&stream->device->lock);
 	/* stream can be drained only when next track has been signalled */
 	if (stream->next_track == false)
 		return -EPERM;