[alsa-devel] 1.1.3 bug report: dmix reports inconsistent status

[Cheng Sun]

Hi all,

The following commit (released in v1.1.3) introduced an issue where
dmix reports its state differently when snd_pcm_state is queried,
compared to snd_pcm_status.

    38a2d2eda880fda9ed5a4a219db498d9c0856d71

(I suspect faf53c197cabeb1eb0fd1f66cd001d1469ebac09 affects dshare
similarly, but this is not tested)

The sample program attached at the bottom of this email demonstrates
this behaviour by printing the following on underrun:

try 1: status_state=3, state=4
try 2: status_state=3, state=4
ALSA lib pcm.c:8306:(snd_pcm_recover) underrun occurred

Cheers,
Cheng


---

#include <assert.h>
#include <alsa/asoundlib.h>
#include <stdint.h>
#define FRAMES 100
int32_t buffer[FRAMES][2];
int main(int argc, char *argv[]) {
    const char *pcmname = argc == 2 ? argv[1] : "default";
    snd_pcm_t *pcm;
    assert( snd_pcm_open(&pcm, pcmname, SND_PCM_STREAM_PLAYBACK, 0) == 0 );
    assert( snd_pcm_set_params(pcm, SND_PCM_FORMAT_S32_LE,
SND_PCM_ACCESS_RW_INTERLEAVED, 2, 48000, 1, 250) == 0 );
    for (;;) {
        snd_pcm_sframes_t written = snd_pcm_writei(pcm, buffer, FRAMES);
        if (written <= 0) {
            snd_pcm_status_t *status;
            snd_pcm_status_alloca(&status);
            assert( snd_pcm_status(pcm, status) == 0 );

            int status_state, state;

            status_state = snd_pcm_status_get_state(status);
            state = snd_pcm_state(pcm);
            printf("try 1: status_state=%d, state=%d\n", status_state, state);

            status_state = snd_pcm_status_get_state(status);
            state = snd_pcm_state(pcm);
            printf("try 2: status_state=%d, state=%d\n", status_state, state);

            assert( snd_pcm_recover(pcm,written,0) == 0 );
        }
    }
}