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@suse.cz Linux Kernel Sound Maintainer ALSA Project, SUSE Labs