On Wed, 19 Sep 2007, Mike Gorse wrote:
> Hi again,
>
> I posted last week because I am getting lockups when portaudio calls
> snd_pcm_drain, and snd_pcm_rate_drain calls snd_pcm_wait on its slave.
>
> Now that I've looked at this more, I'm seeing that it involves dmix, since
> a dmix plugin is behind the rate plugin.
>
> The dmix code in alsa-lib is setting a xrun state because
> snd_pcm_mmap_playback_avail returns a large value.
>
> snd_pcm_wait is then called on the slave of the rate pcm, which is a pcm
> with a type of SND_PCM_TYPE_ROUTE whose slave is the dmix, but the route
> pcm is returning a different value for snd_pcm_mmap_avail than the dmix
> pcm, so it is not triggering snd_pcm_wait to check for a xrun.
>
> The following patch stops snd_pcm_wait from locking up for me, although
> I'm not sure if it is the best way of handling things:
>
> --- src/pcm/pcm.c.orig 2007-09-12 05:20:32.000000000 -0400
> +++ src/pcm/pcm.c 2007-09-19 19:52:10.000000000 -0400
> @@ -2255,7 +2255,7 @@
> */
> int snd_pcm_wait(snd_pcm_t *pcm, int timeout)
> {
> - if (snd_pcm_mmap_avail(pcm) >= pcm->avail_min) {
> + if (snd_pcm_mmap_avail(pcm) >= pcm->avail_min || pcm->type == SND_PCM_TYPE_ROUTE) {
> /* check more precisely */
> switch (snd_pcm_state(pcm)) {
> case SND_PCM_STATE_XRUN:
I think that better fix is to change the code in snd_pcm_rate_drain(). You
can set avail_min to 1 there, so condition in snd_pcm_wait() will match.
Does this patch help?
diff -r 68d71239d651 src/pcm/pcm_rate.c
--- a/src/pcm/pcm_rate.c Thu Sep 20 13:20:03 2007 +0200
+++ b/src/pcm/pcm_rate.c Fri Sep 21 10:14:41 2007 +0200
@@ -1076,10 +1076,10 @@ static int snd_pcm_rate_drain(snd_pcm_t
snd_pcm_uframes_t size, ofs, saved_avail_min;
snd_pcm_sw_params_t sw_params;
- /* temporarily set avail_min to one period */
+ /* temporarily set avail_min to one */
sw_params = rate->sw_params;
saved_avail_min = sw_params.avail_min;
- sw_params.avail_min = rate->gen.slave->period_size;
+ sw_params.avail_min = 1;
snd_pcm_sw_params(rate->gen.slave, &sw_params);
size = rate->appl_ptr - rate->last_commit_ptr;
Jaroslav
-----
Jaroslav Kysela <perex@xxxxxxx>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs
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