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

[Shengjiu Wang]

On Mon, Jun 08, 2015 at 01:31:41PM +0200, Takashi Iwai wrote:
> At Mon, 8 Jun 2015 17:38:11 +0800,
> Shengjiu Wang wrote:
> > 
> > After suspend and resume, the alsa driver is stopped. But if alsa-lib run
> > into snd_pcm_dmix_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>
> > ---
> >  src/pcm/pcm_dmix.c |    6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
> > index babde6a..0cc318e 100644
> > --- a/src/pcm/pcm_dmix.c
> > +++ b/src/pcm/pcm_dmix.c
> > @@ -647,6 +647,12 @@ static int snd_pcm_dmix_drain(snd_pcm_t *pcm)
> >  		if (dmix->state == SND_PCM_STATE_DRAINING) {
> >  			snd_pcm_dmix_sync_area(pcm);
> >  			snd_pcm_wait_nocheck(pcm, -1);
> > +			switch (snd_pcm_state(pcm)) {
> 
> It's better (shorter) to call snd_pcm_state(dmix->spcm) in this case.
> 
> And, I think we should have the check of SND_PCM_STATE_SUSPENDED at
> the beginning of snd_pcm_dmix_drain() before entering to the loop,
> too.
> 
> Last but not least, the very same bug is present for dshare.  Could
> you fix this together?
> 
Ok, I will refine the patch. But one thing I don't understand is that why need
to check the SND_PCM_STATE_SUSPENDED before entering the loop, seems check the
state in the loop can resolve the issue.

Best regards
wang shengjiu
> 
> thanks,
> 
> Takashi
> 
> > +			case SND_PCM_STATE_SUSPENDED:
> > +				return -ESTRPIPE;
> > +			default:
> > +				break;
> > +			}
> >  			snd_pcm_direct_clear_timer_queue(dmix); /* force poll to wait */
> >  		}
> >  	} while (dmix->state == SND_PCM_STATE_DRAINING);
> > -- 
> > 1.7.9.5
> >