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pcm: Skip avail_min check during draining

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snd_pcm_wait() & co checks the current avail value and returns
immediately if it satisfies <= avail_min condition.  It's good in
general except for one situation: draining.  When the draining is
being performed in the non-blocking mode, apps are supposed to wait
via poll(), typically via snd_pcm_wait().  So this ends up with the
busy loop because of the immediate return from snd_pcm_wait().

A simple workaround is to put the PCM state check and ignore the
avail_min condition if it's DRAINING state.  The equivalent check is
found in the kernel xfer code, too.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2018-03-29 09:18:00 +02:00
parent 7f084af4e4
commit d3d42f60a6
1 changed files with 3 additions and 1 deletions
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4
src/pcm/pcm.c
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@ -2751,7 +2751,9 @@ int __snd_pcm_wait_in_lock(snd_pcm_t *pcm, int timeout)
{
int err;
if (!snd_pcm_may_wait_for_avail_min(pcm, snd_pcm_mmap_avail(pcm))) {
/* NOTE: avail_min check can be skipped during draining */
if (__snd_pcm_state(pcm) != SND_PCM_STATE_DRAINING &&
!snd_pcm_may_wait_for_avail_min(pcm, snd_pcm_mmap_avail(pcm))) {
/* check more precisely */
err = pcm_state_to_error(__snd_pcm_state(pcm));
return err < 0 ? err : 1;