pcm: Skip avail_min check during draining

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>

diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index ed47cb5..11aec80 100644 (file)
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -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;