[alsa-devel] [PATCH V2] PCM: snd_pcm_xxxx_drain() maybe blocked after suspend and resume

[Takashi Iwai]

At Fri, 12 Jun 2015 16:15:08 +0800,
Shengjiu Wang wrote:
> 
> After suspend and resume, the alsa driver is stopped. But if alsa-lib run
> into snd_pcm_xxxx_drain(), it need to wait avail >= pcm->stop_threshold,
> otherwise, it will not exit the loop, so finally it is blocked at poll() of
> snd_pcm_wait_nocheck(pcm, -1).
> This patch is to add state check after snd_pcm_wait_nocheck(pcm, -1), if
> the state is SND_PCM_STATE_SUSPENDED, then return error.
> 
> Signed-off-by: Shengjiu Wang <shengjiu.wang at freescale.com>
> ---
> changes in v2:
> - Add state check in beginning of drain()
> - Add fix for pcm_dshare()
> - Mov the state check to the place that is after
> snd_pcm_direct_clear_timer_queue(dmix). That the suspend may happen just before
> calling snd_pcm_direct_clear_timer_queue(dmix), which will force the next poll
> to wait. So move state check to new place may safty.

Applied, thanks.


Takashi

> 
> 
>  src/pcm/pcm_dmix.c   |   14 ++++++++++++++
>  src/pcm/pcm_dshare.c |   14 ++++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
> index babde6a..91148b9 100644
> --- a/src/pcm/pcm_dmix.c
> +++ b/src/pcm/pcm_dmix.c
> @@ -616,6 +616,13 @@ static int snd_pcm_dmix_drain(snd_pcm_t *pcm)
>  	snd_pcm_uframes_t stop_threshold;
>  	int err;
>  
> +	switch (snd_pcm_state(dmix->spcm)) {
> +	case SND_PCM_STATE_SUSPENDED:
> +		return -ESTRPIPE;
> +	default:
> +		break;
> +	}
> +
>  	if (dmix->state == SND_PCM_STATE_OPEN)
>  		return -EBADFD;
>  	if (pcm->mode & SND_PCM_NONBLOCK)
> @@ -648,6 +655,13 @@ static int snd_pcm_dmix_drain(snd_pcm_t *pcm)
>  			snd_pcm_dmix_sync_area(pcm);
>  			snd_pcm_wait_nocheck(pcm, -1);
>  			snd_pcm_direct_clear_timer_queue(dmix); /* force poll to wait */
> +
> +			switch (snd_pcm_state(dmix->spcm)) {
> +			case SND_PCM_STATE_SUSPENDED:
> +				return -ESTRPIPE;
> +			default:
> +				break;
> +			}
>  		}
>  	} while (dmix->state == SND_PCM_STATE_DRAINING);
>  	pcm->stop_threshold = stop_threshold;
> diff --git a/src/pcm/pcm_dshare.c b/src/pcm/pcm_dshare.c
> index 020e6f7..24975d4 100644
> --- a/src/pcm/pcm_dshare.c
> +++ b/src/pcm/pcm_dshare.c
> @@ -367,6 +367,13 @@ static int snd_pcm_dshare_drain(snd_pcm_t *pcm)
>  	snd_pcm_uframes_t stop_threshold;
>  	int err;
>  
> +	switch (snd_pcm_state(dshare->spcm)) {
> +	case SND_PCM_STATE_SUSPENDED:
> +		return -ESTRPIPE;
> +	default:
> +		break;
> +	}
> +
>  	if (dshare->state == SND_PCM_STATE_OPEN)
>  		return -EBADFD;
>  	if (pcm->mode & SND_PCM_NONBLOCK)
> @@ -399,6 +406,13 @@ static int snd_pcm_dshare_drain(snd_pcm_t *pcm)
>  			snd_pcm_dshare_sync_area(pcm);
>  			snd_pcm_wait_nocheck(pcm, -1);
>  			snd_pcm_direct_clear_timer_queue(dshare); /* force poll to wait */
> +
> +			switch (snd_pcm_state(dshare->spcm)) {
> +			case SND_PCM_STATE_SUSPENDED:
> +				return -ESTRPIPE;
> +			default:
> +				break;
> +			}
>  		}
>  	} while (dshare->state == SND_PCM_STATE_DRAINING);
>  	pcm->stop_threshold = stop_threshold;
> -- 
> 1.7.9.5
>