[PATCH v9 02/14] ALSA: virtio: Recover PCM state after a failed start

@@ -26,13 +26,13 @@
  * @hw: Kernel ALSA substream hardware descriptor.
  * @elapsed_period: Kernel work to handle the elapsed period state.
  * @lock: Spinlock that protects fields shared by interrupt handlers and
- *        substream operators.
+ *        substream operators, including @stopped.
  * @buffer_bytes: Current buffer size in bytes.
  * @hw_ptr: Substream hardware pointer value in bytes [0 ... buffer_bytes).
  * @xfer_enabled: Data transfer state (0 - off, 1 - on).
  * @xfer_xrun: Data underflow/overflow state (0 - no xrun, 1 - xrun).
  * @stopped: True if the substream is stopped and must be released on the device
- *           side.
+ *           side; protected by @lock.
  * @suspended: True if the substream is suspended and must be reconfigured on
  *             the device side at resume.
  * @msgs: Allocated I/O messages.

@@ -56,6 +56,8 @@
 	bool xfer_enabled;
 	bool xfer_xrun;
 	bool stopped;
+	/* Successful PREPARE still needs RELEASE; protected by lock. */
+	bool release_required;
 	bool suspended;
 	struct virtio_pcm_msg **msgs;
 	unsigned int nmsgs;

@@ -96,6 +96,15 @@
 
 static int virtsnd_pcm_sync_stop(struct snd_pcm_substream *substream);
 
+static void virtsnd_pcm_start_failed(struct virtio_pcm_substream *vss)
+{
+	scoped_guard(spinlock_irqsave, &vss->lock) {
+		vss->xfer_enabled = false;
+		vss->stopped = true;
+	}
+	vss->substream->runtime->stop_operating = true;
+}
+
 /**
  * virtsnd_pcm_open() - Open the PCM substream.
  * @substream: Kernel ALSA substream.

@@ -115,7 +124,8 @@
 	snd_pcm_hw_constraint_integer(substream->runtime,
 				      SNDRV_PCM_HW_PARAM_PERIODS);
 
-	vss->stopped = !!virtsnd_pcm_msg_pending_num(vss);
+	scoped_guard(spinlock_irqsave, &vss->lock)
+		vss->stopped |= !!vss->msg_count;
 	vss->suspended = false;
 
 	/*

@@ -217,11 +227,23 @@
 {
 	struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream);
 	struct virtio_device *vdev = vss->snd->vdev;
+	unsigned int msg_count;
+	bool stopped;
 	int rc;
 
-	if (virtsnd_pcm_msg_pending_num(vss)) {
+	scoped_guard(spinlock_irqsave, &vss->lock) {
+		msg_count = vss->msg_count;
+		stopped = vss->stopped;
+	}
+	if (msg_count) {
 		dev_err(&vdev->dev, "SID %u: invalid I/O queue state\n",
 			vss->sid);
+		return -EBADFD;
+	}
+	if (stopped) {
+		dev_err(&vdev->dev, "SID %u: stream release failed\n",
+			vss->sid);
+		substream->runtime->stop_operating = true;
 		return -EBADFD;
 	}
 

@@ -273,6 +295,17 @@
 	struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream);
 	struct virtio_device *vdev = vss->snd->vdev;
 	struct virtio_snd_msg *msg;
+	bool stopped;
+	int rc;
+
+	scoped_guard(spinlock_irqsave, &vss->lock)
+		stopped = vss->stopped;
+	if (stopped) {
+		dev_err(&vdev->dev, "SID %u: stream release failed\n",
+			vss->sid);
+		substream->runtime->stop_operating = true;
+		return -EBADFD;
+	}
 
 	if (!vss->suspended) {
 		if (virtsnd_pcm_msg_pending_num(vss)) {

@@ -311,7 +344,12 @@
 	if (!msg)
 		return -ENOMEM;
 
-	return virtsnd_ctl_msg_send_sync(vss->snd, msg);
+	rc = virtsnd_ctl_msg_send_sync(vss->snd, msg);
+	if (!rc) {
+		guard(spinlock_irqsave)(&vss->lock);
+		vss->release_required = true;
+	}
+	return rc;
 }
 
 /**

@@ -338,31 +376,40 @@
 
 		scoped_guard(spinlock_irqsave, &queue->lock) {
 			guard(spinlock)(&vss->lock);
+			if (vss->stopped) {
+				substream->runtime->stop_operating = true;
+				return -EBADFD;
+			}
 			if (vss->direction == SNDRV_PCM_STREAM_CAPTURE)
 				rc = virtsnd_pcm_msg_send(vss, 0, vss->buffer_bytes);
-			if (rc)
+			if (rc) {
+				vss->stopped = true;
+				substream->runtime->stop_operating = true;
 				return rc;
+			}
 			vss->xfer_enabled = true;
 		}
 
 		msg = virtsnd_pcm_ctl_msg_alloc(vss, VIRTIO_SND_R_PCM_START,
 						GFP_KERNEL);
 		if (!msg) {
-			guard(spinlock_irqsave)(&vss->lock);
-			vss->xfer_enabled = false;
-
+			virtsnd_pcm_start_failed(vss);
 			return -ENOMEM;
 		}
 
-		return virtsnd_ctl_msg_send_sync(snd, msg);
+		rc = virtsnd_ctl_msg_send_sync(snd, msg);
+		if (rc)
+			virtsnd_pcm_start_failed(vss);
+
+		return rc;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 		vss->suspended = true;
 		fallthrough;
 	case SNDRV_PCM_TRIGGER_STOP:
-		vss->stopped = true;
-		fallthrough;
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		scoped_guard(spinlock_irqsave, &vss->lock) {
+			if (command != SNDRV_PCM_TRIGGER_PAUSE_PUSH)
+				vss->stopped = true;
 			vss->xfer_enabled = false;
 		}
 

@@ -393,21 +440,34 @@
 	struct virtio_snd *snd = vss->snd;
 	struct virtio_snd_msg *msg;
 	unsigned int js = msecs_to_jiffies(virtsnd_msg_timeout_ms);
+	bool need_release;
 	int rc;
 
+	scoped_guard(spinlock_irqsave, &vss->lock) {
+		vss->xfer_enabled = false;
+		need_release = vss->release_required;
+		if (need_release)
+			vss->stopped = true;
+	}
 	cancel_work_sync(&vss->elapsed_period);
 
-	if (!vss->stopped)
-		return 0;
-
-	msg = virtsnd_pcm_ctl_msg_alloc(vss, VIRTIO_SND_R_PCM_RELEASE,
-					GFP_KERNEL);
-	if (!msg)
-		return -ENOMEM;
-
-	rc = virtsnd_ctl_msg_send_sync(snd, msg);
-	if (rc)
-		return rc;
+	if (need_release) {
+		msg = virtsnd_pcm_ctl_msg_alloc(vss, VIRTIO_SND_R_PCM_RELEASE,
+						GFP_KERNEL);
+		if (!msg) {
+			substream->runtime->stop_operating = true;
+			return -ENOMEM;
+		}
+
+		rc = virtsnd_ctl_msg_send_sync(snd, msg);
+		if (rc) {
+			substream->runtime->stop_operating = true;
+			return rc;
+		}
+
+		scoped_guard(spinlock_irqsave, &vss->lock)
+			vss->release_required = false;
+	}
 
 	/*
 	 * The spec states that upon receipt of the RELEASE command "the device

@@ -421,11 +481,13 @@
 	if (rc <= 0) {
 		dev_warn(&snd->vdev->dev, "SID %u: failed to flush I/O queue\n",
 			 vss->sid);
+		substream->runtime->stop_operating = true;
 
 		return !rc ? -ETIMEDOUT : rc;
 	}
 
-	vss->stopped = false;
+	scoped_guard(spinlock_irqsave, &vss->lock)
+		vss->stopped = false;
 
 	return 0;
 }