[PATCH v5 0/4] Propagate errors out from compressed streams

[PATCH v5 0/4] Propagate errors out from compressed streams

[Charles Keepax]

If the DSP suffers an unrecoverable error, the driver likely
knows about this, however the framework may not get informed
because errors returned from pointer requests are ignored within
the framework.

Things work out fine if user-space is doing a read as reads
return error status back to user-space so the user can find out
that things have gone bad. However, if user-space is doing an
avail request there is no path for the error to come back up to
user-space. The pointer request returns zero available data, so a
read never happens and we basically just end up sitting waiting
for data on a stream that we know full well has died.

This patch set attempts to address this and ensure that errors
are fully propagated to user-space and we don't ever end up wait
for data that will never come.

Changes since v4:
 - Fix issue noticed by Vinod whereby the error state was being
   overwritten when snd_compr_stop was called

It might be easiest to put the ASoC changes through Mark's tree
as there are some merge conflicts otherwise, as such I have based
this series on Mark's tree.

Thanks,
Charles

Charles Keepax (4):
  ALSA: compress: Replace complex if statement with switch
  ALSA: compress: Add function to indicate the stream has gone bad
  ASoC: wm_adsp: Use new snd_compr_stop_error to signal stream failure
  ASoC: compress: Pass error out of soc_compr_pointer

 include/sound/compress_driver.h |  5 +++
 sound/core/compress_offload.c   | 79 ++++++++++++++++++++++++++++++++++++++---
 sound/soc/codecs/wm_adsp.c      | 11 ++++--
 sound/soc/soc-compress.c        |  5 +--
 4 files changed, 91 insertions(+), 9 deletions(-)

-- 
2.1.4

[PATCH v5 1/4] ALSA: compress: Replace complex if statement with switch

[Charles Keepax]

A switch statement looks a bit cleaner than an if statement
spread over 3 lines, as such update this to a switch.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
---
 sound/core/compress_offload.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index a9933c0..507071d 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -288,9 +288,12 @@ static ssize_t snd_compr_write(struct file *f, const char __user *buf,
 	stream = &data->stream;
 	mutex_lock(&stream->device->lock);
 	/* write is allowed when stream is running or has been steup */
-	if (stream->runtime->state != SNDRV_PCM_STATE_SETUP &&
-	    stream->runtime->state != SNDRV_PCM_STATE_PREPARED &&
-			stream->runtime->state != SNDRV_PCM_STATE_RUNNING) {
+	switch (stream->runtime->state) {
+	case SNDRV_PCM_STATE_SETUP:
+	case SNDRV_PCM_STATE_PREPARED:
+	case SNDRV_PCM_STATE_RUNNING:
+		break;
+	default:
 		mutex_unlock(&stream->device->lock);
 		return -EBADFD;
 	}
-- 
2.1.4

[PATCH v5 2/4] ALSA: compress: Add function to indicate the stream has gone bad

[Charles Keepax]

Currently, the avail IOCTL doesn't pass any error status, which
means typically on error it simply shows no data available. This
can lead to situations where user-space is waiting indefinitely
for data that will never come as the DSP has suffered an
unrecoverable error.

Add snd_compr_stop_error which end drivers can call to indicate
the stream has suffered an unrecoverable error and stop it. The
avail and poll IOCTLs are then updated to report if the stream is
in an error state to user-space. Allowing the error to propagate
out. Processing of the actual snd_compr_stop needs to be deferred
to a worker thread as the end driver may detect the errors during
an existing operation callback.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
---
 include/sound/compress_driver.h |  5 +++
 sound/core/compress_offload.c   | 70 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/include/sound/compress_driver.h b/include/sound/compress_driver.h
index c0abcdc..cee8c00 100644
--- a/include/sound/compress_driver.h
+++ b/include/sound/compress_driver.h
@@ -68,6 +68,7 @@ struct snd_compr_runtime {
  * @ops: pointer to DSP callbacks
  * @runtime: pointer to runtime structure
  * @device: device pointer
+ * @error_work: delayed work used when closing the stream due to an error
  * @direction: stream direction, playback/recording
  * @metadata_set: metadata set flag, true when set
  * @next_track: has userspace signal next track transition, true when set
@@ -78,6 +79,7 @@ struct snd_compr_stream {
 	struct snd_compr_ops *ops;
 	struct snd_compr_runtime *runtime;
 	struct snd_compr *device;
+	struct delayed_work error_work;
 	enum snd_compr_direction direction;
 	bool metadata_set;
 	bool next_track;
@@ -187,4 +189,7 @@ static inline void snd_compr_drain_notify(struct snd_compr_stream *stream)
 	wake_up(&stream->runtime->sleep);
 }
 
+int snd_compr_stop_error(struct snd_compr_stream *stream,
+			 snd_pcm_state_t state);
+
 #endif
diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index 507071d..28043bb 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -67,6 +67,8 @@ struct snd_compr_file {
 	struct snd_compr_stream stream;
 };
 
+static void error_delayed_work(struct work_struct *work);
+
 /*
  * a note on stream states used:
  * we use following states in the compressed core
@@ -123,6 +125,9 @@ static int snd_compr_open(struct inode *inode, struct file *f)
 		snd_card_unref(compr->card);
 		return -ENOMEM;
 	}
+
+	INIT_DELAYED_WORK(&data->stream.error_work, error_delayed_work);
+
 	data->stream.ops = compr->ops;
 	data->stream.direction = dirn;
 	data->stream.private_data = compr->private_data;
@@ -153,6 +158,8 @@ static int snd_compr_free(struct inode *inode, struct file *f)
 	struct snd_compr_file *data = f->private_data;
 	struct snd_compr_runtime *runtime = data->stream.runtime;
 
+	cancel_delayed_work_sync(&data->stream.error_work);
+
 	switch (runtime->state) {
 	case SNDRV_PCM_STATE_RUNNING:
 	case SNDRV_PCM_STATE_DRAINING:
@@ -237,6 +244,15 @@ snd_compr_ioctl_avail(struct snd_compr_stream *stream, unsigned long arg)
 	avail = snd_compr_calc_avail(stream, &ioctl_avail);
 	ioctl_avail.avail = avail;
 
+	switch (stream->runtime->state) {
+	case SNDRV_PCM_STATE_OPEN:
+		return -EBADFD;
+	case SNDRV_PCM_STATE_XRUN:
+		return -EPIPE;
+	default:
+		break;
+	}
+
 	if (copy_to_user((__u64 __user *)arg,
 				&ioctl_avail, sizeof(ioctl_avail)))
 		return -EFAULT;
@@ -346,11 +362,13 @@ static ssize_t snd_compr_read(struct file *f, char __user *buf,
 	switch (stream->runtime->state) {
 	case SNDRV_PCM_STATE_OPEN:
 	case SNDRV_PCM_STATE_PREPARED:
-	case SNDRV_PCM_STATE_XRUN:
 	case SNDRV_PCM_STATE_SUSPENDED:
 	case SNDRV_PCM_STATE_DISCONNECTED:
 		retval = -EBADFD;
 		goto out;
+	case SNDRV_PCM_STATE_XRUN:
+		retval = -EPIPE;
+		goto out;
 	}
 
 	avail = snd_compr_get_avail(stream);
@@ -400,10 +418,18 @@ static unsigned int snd_compr_poll(struct file *f, poll_table *wait)
 		return -EFAULT;
 
 	mutex_lock(&stream->device->lock);
-	if (stream->runtime->state == SNDRV_PCM_STATE_OPEN) {
+
+	switch (stream->runtime->state) {
+	case SNDRV_PCM_STATE_OPEN:
 		retval = -EBADFD;
 		goto out;
+	case SNDRV_PCM_STATE_XRUN:
+		retval = -EPIPE;
+		goto out;
+	default:
+		break;
 	}
+
 	poll_wait(f, &stream->runtime->sleep, wait);
 
 	avail = snd_compr_get_avail(stream);
@@ -423,6 +449,9 @@ static unsigned int snd_compr_poll(struct file *f, poll_table *wait)
 		if (avail >= stream->runtime->fragment_size)
 			retval = snd_compr_get_poll(stream);
 		break;
+	case SNDRV_PCM_STATE_XRUN:
+		retval = -EPIPE;
+		break;
 	default:
 		if (stream->direction == SND_COMPRESS_PLAYBACK)
 			retval = POLLOUT | POLLWRNORM | POLLERR;
@@ -701,6 +730,43 @@ static int snd_compr_stop(struct snd_compr_stream *stream)
 	return retval;
 }
 
+static void error_delayed_work(struct work_struct *work)
+{
+	struct snd_compr_stream *stream;
+
+	stream = container_of(work, struct snd_compr_stream, error_work.work);
+
+	mutex_lock(&stream->device->lock);
+
+	if (!stream->ops->trigger(stream, SNDRV_PCM_TRIGGER_STOP))
+		wake_up(&stream->runtime->sleep);
+
+	mutex_unlock(&stream->device->lock);
+}
+
+/*
+ * snd_compr_stop_error: Report a fatal error on a stream
+ * @stream: pointer to stream
+ * @state: state to transition the stream to
+ *
+ * Stop the stream and set its state.
+ *
+ * Should be called with compressed device lock held.
+ */
+int snd_compr_stop_error(struct snd_compr_stream *stream,
+			 snd_pcm_state_t state)
+{
+	if (stream->runtime->state == state)
+		return 0;
+
+	stream->runtime->state = state;
+
+	queue_delayed_work(system_power_efficient_wq, &stream->error_work, 0);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_compr_stop_error);
+
 static int snd_compress_wait_for_drain(struct snd_compr_stream *stream)
 {
 	int ret;
-- 
2.1.4

Re: [PATCH v5 2/4] ALSA: compress: Add function to indicate the stream has gone bad

[Vinod Koul]

On Wed, Apr 20, 2016 at 01:40:01PM +0100, Charles Keepax wrote:
> Currently, the avail IOCTL doesn't pass any error status, which
> means typically on error it simply shows no data available. This
> can lead to situations where user-space is waiting indefinitely
> for data that will never come as the DSP has suffered an
> unrecoverable error.
> 
> Add snd_compr_stop_error which end drivers can call to indicate
> the stream has suffered an unrecoverable error and stop it. The
> avail and poll IOCTLs are then updated to report if the stream is
> in an error state to user-space. Allowing the error to propagate
> out. Processing of the actual snd_compr_stop needs to be deferred
> to a worker thread as the end driver may detect the errors during
> an existing operation callback.

Acked-by: Vinod Koul <vinod.koul@intel.com>

Btw are you patching tinycompress as well to handle EPIPE?

Thanks
-- 
~Vinod

Re: [PATCH v5 2/4] ALSA: compress: Add function to indicate the stream has gone bad

[Charles Keepax]

On Wed, Apr 20, 2016 at 06:38:51PM +0530, Vinod Koul wrote:
> On Wed, Apr 20, 2016 at 01:40:01PM +0100, Charles Keepax wrote:
> > Currently, the avail IOCTL doesn't pass any error status, which
> > means typically on error it simply shows no data available. This
> > can lead to situations where user-space is waiting indefinitely
> > for data that will never come as the DSP has suffered an
> > unrecoverable error.
> > 
> > Add snd_compr_stop_error which end drivers can call to indicate
> > the stream has suffered an unrecoverable error and stop it. The
> > avail and poll IOCTLs are then updated to report if the stream is
> > in an error state to user-space. Allowing the error to propagate
> > out. Processing of the actual snd_compr_stop needs to be deferred
> > to a worker thread as the end driver may detect the errors during
> > an existing operation callback.
> 
> Acked-by: Vinod Koul <vinod.koul@intel.com>
> 
> Btw are you patching tinycompress as well to handle EPIPE?

I hadn't planned on it but I am happy to do so. The current
behaviour was sufficient for our needs in that it reports the
error and shuts the stream.

Are you thinking of just printing that a over/under run occurred
or do you want to try and add some recovery code as well?

Thanks,
Charles

Re: [PATCH v5 2/4] ALSA: compress: Add function to indicate the stream has gone bad

[Vinod Koul]

On Wed, Apr 20, 2016 at 03:54:46PM +0100, Charles Keepax wrote:
> On Wed, Apr 20, 2016 at 06:38:51PM +0530, Vinod Koul wrote:
> > On Wed, Apr 20, 2016 at 01:40:01PM +0100, Charles Keepax wrote:
> > > Currently, the avail IOCTL doesn't pass any error status, which
> > > means typically on error it simply shows no data available. This
> > > can lead to situations where user-space is waiting indefinitely
> > > for data that will never come as the DSP has suffered an
> > > unrecoverable error.
> > > 
> > > Add snd_compr_stop_error which end drivers can call to indicate
> > > the stream has suffered an unrecoverable error and stop it. The
> > > avail and poll IOCTLs are then updated to report if the stream is
> > > in an error state to user-space. Allowing the error to propagate
> > > out. Processing of the actual snd_compr_stop needs to be deferred
> > > to a worker thread as the end driver may detect the errors during
> > > an existing operation callback.
> > 
> > Acked-by: Vinod Koul <vinod.koul@intel.com>
> > 
> > Btw are you patching tinycompress as well to handle EPIPE?
> 
> I hadn't planned on it but I am happy to do so. The current
> behaviour was sufficient for our needs in that it reports the
> error and shuts the stream.
> 
> Are you thinking of just printing that a over/under run occurred
> or do you want to try and add some recovery code as well?

To start with yes adding prints would help. Adding code to handle EPIPE
would be good and propagating that to user.

>From lib, certainly we want to see this error progated so that upper layers
can do recovery

Recovery is tricky here as we are doing compressed data so essentially new
data has to be on frame boundary, so upper layers should decide.

Thanks
-- 
~Vinod

Re: [PATCH v5 2/4] ALSA: compress: Add function to indicate the stream has gone bad

[Pierre-Louis Bossart]

> + * snd_compr_stop_error: Report a fatal error on a stream
> + * @stream: pointer to stream
> + * @state: state to transition the stream to
> + *
> + * Stop the stream and set its state.
> + *
> + * Should be called with compressed device lock held.
> + */
> +int snd_compr_stop_error(struct snd_compr_stream *stream,
> +			 snd_pcm_state_t state)
> +{
> +	if (stream->runtime->state == state)
> +		return 0;
> +
> +	stream->runtime->state = state;

Minor nit-pick: should there be a consistency check to make sure the new 
state makes sense - or maybe just a log to help debug? e.g. XRUN should 
only come if the state in run or draining stages, applying the new state 
unconditionally could lead to issues.
And question for my education since I see no lock/mutex: is the state 
always consistent or is there a risk of this state being changed while 
some other thread or interrupt handling modifies it was well?

Re: [PATCH v5 2/4] ALSA: compress: Add function to indicate the stream has gone bad

[Charles Keepax]

On Wed, Apr 20, 2016 at 11:10:21AM -0500, Pierre-Louis Bossart wrote:
> 
> >+ * snd_compr_stop_error: Report a fatal error on a stream
> >+ * @stream: pointer to stream
> >+ * @state: state to transition the stream to
> >+ *
> >+ * Stop the stream and set its state.
> >+ *
> >+ * Should be called with compressed device lock held.
> >+ */
> >+int snd_compr_stop_error(struct snd_compr_stream *stream,
> >+			 snd_pcm_state_t state)
> >+{
> >+	if (stream->runtime->state == state)
> >+		return 0;
> >+
> >+	stream->runtime->state = state;
> 
> Minor nit-pick: should there be a consistency check to make sure the new
> state makes sense - or maybe just a log to help debug? e.g. XRUN should only
> come if the state in run or draining stages, applying the new state
> unconditionally could lead to issues.

I think given the function can now report more than just a XRUN
it probably makes sense to set it unconditionally. As you might
be reporting some error that doesn't require the stream to be
running.

It probably would make sense to only call trigger with
TRIGGER_STOP if the stream is already running through. How about
I add a check for the state in the delayed work? And I can
certainly add a print to say the state was set, that probably
makes sense anyway as it is an error being reported.

> And question for my education since I see no lock/mutex: is the state always
> consistent or is there a risk of this state being changed while some other
> thread or interrupt handling modifies it was well?

As the comment says it is expected the lock should be held when
calling the function. I could put a lockdep assert in, if we want
to be cautious on this front?

Thanks,
Charles

Re: [PATCH v5 2/4] ALSA: compress: Add function to indicate the stream has gone bad

[Pierre-Louis Bossart]

On 04/21/2016 03:26 AM, Charles Keepax wrote:
> On Wed, Apr 20, 2016 at 11:10:21AM -0500, Pierre-Louis Bossart wrote:
>>> + * snd_compr_stop_error: Report a fatal error on a stream
>>> + * @stream: pointer to stream
>>> + * @state: state to transition the stream to
>>> + *
>>> + * Stop the stream and set its state.
>>> + *
>>> + * Should be called with compressed device lock held.
>>> + */
>>> +int snd_compr_stop_error(struct snd_compr_stream *stream,
>>> +			 snd_pcm_state_t state)
>>> +{
>>> +	if (stream->runtime->state == state)
>>> +		return 0;
>>> +
>>> +	stream->runtime->state = state;
>> Minor nit-pick: should there be a consistency check to make sure the new
>> state makes sense - or maybe just a log to help debug? e.g. XRUN should only
>> come if the state in run or draining stages, applying the new state
>> unconditionally could lead to issues.
> I think given the function can now report more than just a XRUN
> it probably makes sense to set it unconditionally. As you might
> be reporting some error that doesn't require the stream to be
> running.
>
> It probably would make sense to only call trigger with
> TRIGGER_STOP if the stream is already running through. How about
> I add a check for the state in the delayed work? And I can
> certainly add a print to say the state was set, that probably
> makes sense anyway as it is an error being reported.
ok, a log would be fine.
>
>> And question for my education since I see no lock/mutex: is the state always
>> consistent or is there a risk of this state being changed while some other
>> thread or interrupt handling modifies it was well?
> As the comment says it is expected the lock should be held when
> calling the function. I could put a lockdep assert in, if we want
> to be cautious on this front?
I missed the comment, thanks the clarification.
No objections from me, this sounds good.

[PATCH v5 3/4] ASoC: wm_adsp: Use new snd_compr_stop_error to signal stream failure

[Charles Keepax]

If we encounter a fatal error on the compressed stream call the new
snd_compr_stop_error to shutdown the stream and allow the core to
inform user-space that the stream is no longer valid.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
---
 sound/soc/codecs/wm_adsp.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/sound/soc/codecs/wm_adsp.c b/sound/soc/codecs/wm_adsp.c
index 3ac2e1f..d221ac9 100644
--- a/sound/soc/codecs/wm_adsp.c
+++ b/sound/soc/codecs/wm_adsp.c
@@ -2913,6 +2913,7 @@ int wm_adsp_compr_pointer(struct snd_compr_stream *stream,
 	}
 
 	if (compr->buf->error) {
+		snd_compr_stop_error(stream, SNDRV_PCM_STATE_XRUN);
 		ret = -EIO;
 		goto out;
 	}
@@ -2930,8 +2931,12 @@ int wm_adsp_compr_pointer(struct snd_compr_stream *stream,
 		 */
 		if (buf->avail < wm_adsp_compr_frag_words(compr)) {
 			ret = wm_adsp_buffer_get_error(buf);
-			if (ret < 0)
+			if (ret < 0) {
+				if (compr->buf->error)
+					snd_compr_stop_error(stream,
+							SNDRV_PCM_STATE_XRUN);
 				goto out;
+			}
 
 			ret = wm_adsp_buffer_reenable_irq(buf);
 			if (ret < 0) {
@@ -3029,8 +3034,10 @@ static int wm_adsp_compr_read(struct wm_adsp_compr *compr,
 	if (!compr->buf)
 		return -ENXIO;
 
-	if (compr->buf->error)
+	if (compr->buf->error) {
+		snd_compr_stop_error(compr->stream, SNDRV_PCM_STATE_XRUN);
 		return -EIO;
+	}
 
 	count /= WM_ADSP_DATA_WORD_SIZE;
 
-- 
2.1.4

Re: [PATCH v5 3/4] ASoC: wm_adsp: Use new snd_compr_stop_error to signal stream failure

[Vinod Koul]

On Wed, Apr 20, 2016 at 01:40:02PM +0100, Charles Keepax wrote:
> If we encounter a fatal error on the compressed stream call the new
> snd_compr_stop_error to shutdown the stream and allow the core to
> inform user-space that the stream is no longer valid.

Reviewed-by: Vinod Koul <vinod.koul@intel.com>


-- 
~Vinod

[PATCH v5 4/4] ASoC: compress: Pass error out of soc_compr_pointer

[Charles Keepax]

Both soc_compr_pointer and the platform driver pointer callback return
ints but current soc_compr_pointer always returns 0. Update this so we
return the actual value from the platform driver callback. This doesn't
fix any issues simply makes the code more consistent.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
---
 sound/soc/soc-compress.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sound/soc/soc-compress.c b/sound/soc/soc-compress.c
index 875733c..d2df46c 100644
--- a/sound/soc/soc-compress.c
+++ b/sound/soc/soc-compress.c
@@ -530,14 +530,15 @@ static int soc_compr_pointer(struct snd_compr_stream *cstream,
 {
 	struct snd_soc_pcm_runtime *rtd = cstream->private_data;
 	struct snd_soc_platform *platform = rtd->platform;
+	int ret = 0;
 
 	mutex_lock_nested(&rtd->pcm_mutex, rtd->pcm_subclass);
 
 	if (platform->driver->compr_ops && platform->driver->compr_ops->pointer)
-		 platform->driver->compr_ops->pointer(cstream, tstamp);
+		ret = platform->driver->compr_ops->pointer(cstream, tstamp);
 
 	mutex_unlock(&rtd->pcm_mutex);
-	return 0;
+	return ret;
 }
 
 static int soc_compr_copy(struct snd_compr_stream *cstream,
-- 
2.1.4

Re: [PATCH v5 0/4] Propagate errors out from compressed streams

[Takashi Iwai]

On Wed, 20 Apr 2016 14:39:59 +0200,
Charles Keepax wrote:
> 
> If the DSP suffers an unrecoverable error, the driver likely
> knows about this, however the framework may not get informed
> because errors returned from pointer requests are ignored within
> the framework.
> 
> Things work out fine if user-space is doing a read as reads
> return error status back to user-space so the user can find out
> that things have gone bad. However, if user-space is doing an
> avail request there is no path for the error to come back up to
> user-space. The pointer request returns zero available data, so a
> read never happens and we basically just end up sitting waiting
> for data on a stream that we know full well has died.
> 
> This patch set attempts to address this and ensure that errors
> are fully propagated to user-space and we don't ever end up wait
> for data that will never come.
> 
> Changes since v4:
>  - Fix issue noticed by Vinod whereby the error state was being
>    overwritten when snd_compr_stop was called
> 
> It might be easiest to put the ASoC changes through Mark's tree
> as there are some merge conflicts otherwise, as such I have based
> this series on Mark's tree.

If it goes through Mark's tree, feel free to take my ack to these
patches:
  Acked-by: Takashi Iwai <tiwai@suse.de>

Or if it's easier through my tree, let me know.


thanks,

Takashi