ALSA: compress: fix drain calls blocking other compress functions (v6)

The drain and drain_notify callback were blocked by low level driver
until the draining was complete. Due to this being invoked with big
fat mutex held, others ops like reading timestamp, calling pause, drop
were blocked.

So to fix this we add a new snd_compr_drain_notify() API. This would
be required to be invoked by low level driver when drain or partial
drain has been completed by the DSP. Thus we make the drain and
partial_drain callback as non blocking and driver returns immediately
after notifying DSP.  The waiting is done while releasing the lock so
that other ops can go ahead.

[ The commit 917f4b5cba78 was wrongly applied from the preliminary
  patch.  This commit corrects to the final version.
  Sorry for inconvenience!  -- tiwai ]

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
CC: stable@vger.kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/compress_driver.h

@@ -48,8 +48,6 @@ struct snd_compr_ops;
  *	the ring buffer
  * @total_bytes_transferred: cumulative bytes transferred by offload DSP
  * @sleep: poll sleep
- * @wait: drain wait queue
- * @drain_wake: condition for drain wake
  */
 struct snd_compr_runtime {
 	snd_pcm_state_t state;
@@ -61,8 +59,6 @@ struct snd_compr_runtime {
 	u64 total_bytes_available;
 	u64 total_bytes_transferred;
 	wait_queue_head_t sleep;
-	wait_queue_head_t wait;
-	unsigned int drain_wake;
 	void *private_data;
 };
 
@@ -177,10 +173,11 @@ static inline void snd_compr_fragment_elapsed(struct snd_compr_stream *stream)
 
 static inline void snd_compr_drain_notify(struct snd_compr_stream *stream)
 {
-	snd_BUG_ON(!stream);
+	if (snd_BUG_ON(!stream))
+		return;
 
-	stream->runtime->drain_wake = 1;
-	wake_up(&stream->runtime->wait);
+	stream->runtime->state = SNDRV_PCM_STATE_SETUP;
+	wake_up(&stream->runtime->sleep);
 }
 
 #endif

sound/core/compress_offload.c

@@ -123,7 +123,6 @@ static int snd_compr_open(struct inode *inode, struct file *f)
 	}
 	runtime->state = SNDRV_PCM_STATE_OPEN;
 	init_waitqueue_head(&runtime->sleep);
-	init_waitqueue_head(&runtime->wait);
 	data->stream.runtime = runtime;
 	f->private_data = (void *)data;
 	mutex_lock(&compr->lock);
@@ -681,8 +680,6 @@ static int snd_compr_stop(struct snd_compr_stream *stream)
 		return -EPERM;
 	retval = stream->ops->trigger(stream, SNDRV_PCM_TRIGGER_STOP);
 	if (!retval) {
-		stream->runtime->state = SNDRV_PCM_STATE_SETUP;
-		wake_up(&stream->runtime->sleep);
 		snd_compr_drain_notify(stream);
 		stream->runtime->total_bytes_available = 0;
 		stream->runtime->total_bytes_transferred = 0;
@@ -692,6 +689,8 @@ static int snd_compr_stop(struct snd_compr_stream *stream)
 
 static int snd_compress_wait_for_drain(struct snd_compr_stream *stream)
 {
+	int ret;
+
 	/*
 	 * We are called with lock held. So drop the lock while we wait for
 	 * drain complete notfication from the driver
@@ -703,12 +702,24 @@ static int snd_compress_wait_for_drain(struct snd_compr_stream *stream)
 	stream->runtime->state = SNDRV_PCM_STATE_DRAINING;
 	mutex_unlock(&stream->device->lock);
 
-	wait_event(stream->runtime->wait, stream->runtime->drain_wake);
+	/* we wait for drain to complete here, drain can return when
+	 * interruption occurred, wait returned error or success.
+	 * For the first two cases we don't do anything different here and
+	 * return after waking up
+	 */
+
+	ret = wait_event_interruptible(stream->runtime->sleep,
+			(stream->runtime->state != SNDRV_PCM_STATE_DRAINING));
+	if (ret == -ERESTARTSYS)
+		pr_debug("wait aborted by a signal");
+	else if (ret)
+		pr_debug("wait for drain failed with %d\n", ret);
+
 
 	wake_up(&stream->runtime->sleep);
 	mutex_lock(&stream->device->lock);
 
-	return 0;
+	return ret;
 }
 
 static int snd_compr_drain(struct snd_compr_stream *stream)
@@ -719,17 +730,14 @@ static int snd_compr_drain(struct snd_compr_stream *stream)
 			stream->runtime->state == SNDRV_PCM_STATE_SETUP)
 		return -EPERM;
 
-	stream->runtime->drain_wake = 0;
 	retval = stream->ops->trigger(stream, SND_COMPR_TRIGGER_DRAIN);
 	if (retval) {
-		pr_err("SND_COMPR_TRIGGER_DRAIN failed %d\n", retval);
+		pr_debug("SND_COMPR_TRIGGER_DRAIN failed %d\n", retval);
 		wake_up(&stream->runtime->sleep);
 		return retval;
 	}
 
-	retval = snd_compress_wait_for_drain(stream);
-	stream->runtime->state = SNDRV_PCM_STATE_SETUP;
-	return retval;
+	return snd_compress_wait_for_drain(stream);
 }
 
 static int snd_compr_next_track(struct snd_compr_stream *stream)
@@ -764,10 +772,9 @@ static int snd_compr_partial_drain(struct snd_compr_stream *stream)
 	if (stream->next_track == false)
 		return -EPERM;
 
-	stream->runtime->drain_wake = 0;
 	retval = stream->ops->trigger(stream, SND_COMPR_TRIGGER_PARTIAL_DRAIN);
 	if (retval) {
-		pr_err("Partial drain returned failure\n");
+		pr_debug("Partial drain returned failure\n");
 		wake_up(&stream->runtime->sleep);
 		return retval;
 	}