[alsa-devel] [PATCH 2/9] ALSA: compress: use mutex in drain

[Takashi Iwai]

At Tue, 27 Aug 2013 12:10:32 +0530,
Vinod Koul wrote:
> 
> Since we dont have lock over the function, we need to aquire mutex when checking
> and modfying states in drain and partial_drain handlers
> 
> Signed-off-by: Vinod Koul <vinod.koul at intel.com>
> Cc: <stable at vger.kernel.org>
> ---
>  sound/core/compress_offload.c |   22 +++++++++++++++++++---
>  1 files changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
> index 868aefd..e640f8c 100644
> --- a/sound/core/compress_offload.c
> +++ b/sound/core/compress_offload.c
> @@ -676,18 +676,29 @@ static int snd_compr_stop(struct snd_compr_stream *stream)
>  	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);

Why release the lock here?  The trigger callback is called within this
mutex lock in other places.


Takashi

> +	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;
>  }
>  
> @@ -716,9 +727,14 @@ static int snd_compr_next_track(struct snd_compr_stream *stream)
>  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;
> -- 
> 1.7.0.4
>