1.1.3 bug report: dmix reports inconsistent status

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 );
        }
    }
}

Re: 1.1.3 bug report: dmix reports inconsistent status

[Cheng Sun]

On 24 May 2017 at 20:18, Cheng Sun <chengsun9@gmail.com> wrote:
> 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

Just realised that my original sample program had a slight flaw
(snd_pcm_status only called once). Here's the corrected version, which
still exhibits the erroneous behaviour.

(Also to clarify, this problem is still present in v1.1.4 and master.)

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);

            int status_state, state;

            assert( snd_pcm_status(pcm, status) == 0 );
            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);

            assert( snd_pcm_status(pcm, status) == 0 );
            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 );
        }
    }
}