Delayed start for dmix

Introducing a private state for the delayed start of PCM stream.
This problem occurs when the rate plugin doesn't feed the data
properly before triggering START.  This results in weird problems,
e.g. an inifinte loop of artsd eating 100% CPU time.

To solve this problem, the state is marked as "pending" when no
data appears at the trigger, and the stream is started later at
the mmap commit.

diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
index a913c3351aae2d110ff3a868c068d3e57aaf9c45..efdfeaa42e88aeacad5e9cc29ffd567b969fea34 100644 (file)
--- a/src/pcm/pcm_dmix.c
+++ b/src/pcm/pcm_dmix.c
@@ -49,6 +49,9 @@
 const char *_snd_module_pcm_dmix = "";
 #endif
 
+/* start is pending - this state happens when rate plugin does a delayed commit */
+#define STATE_RUN_PENDING      1024
+
 /*
  *
  */
@@ -300,8 +303,15 @@ static int snd_pcm_dmix_status(snd_pcm_t *pcm, snd_pcm_status_t * status)
                break;
        }
        memset(status, 0, sizeof(*status));
-       state = snd_pcm_state(dmix->spcm);
-       status->state = state == SNDRV_PCM_STATE_RUNNING ? dmix->state : state;
+       if (dmix->state == STATE_RUN_PENDING)
+               status->state = SNDRV_PCM_STATE_RUNNING;
+       else {
+               state = snd_pcm_state(dmix->spcm);
+               if (state == SNDRV_PCM_STATE_RUNNING)
+                       status->state = dmix->state;
+               else
+                       status->state = state;
+       }
        status->trigger_tstamp = dmix->trigger_tstamp;
        status->tstamp = snd_pcm_hw_fast_tstamp(dmix->spcm);
        status->avail = snd_pcm_mmap_playback_avail(pcm);
@@ -322,6 +332,8 @@ static snd_pcm_state_t snd_pcm_dmix_state(snd_pcm_t *pcm)
        default:
                break;
        }
+       if (dmix->state == STATE_RUN_PENDING)
+               return SNDRV_PCM_STATE_RUNNING;
        return dmix->state;
 }
 
@@ -338,6 +350,7 @@ static int snd_pcm_dmix_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delayp)
                        return err;
        case SNDRV_PCM_STATE_PREPARED:
        case SNDRV_PCM_STATE_SUSPENDED:
+       case STATE_RUN_PENDING:
                *delayp = snd_pcm_mmap_playback_hw_avail(pcm);
                return 0;
        case SNDRV_PCM_STATE_XRUN:
@@ -359,6 +372,7 @@ static int snd_pcm_dmix_hwsync(snd_pcm_t *pcm)
                return snd_pcm_dmix_sync_ptr(pcm);
        case SNDRV_PCM_STATE_PREPARED:
        case SNDRV_PCM_STATE_SUSPENDED:
+       case STATE_RUN_PENDING:
                return 0;
        case SNDRV_PCM_STATE_XRUN:
                return -EPIPE;
@@ -399,18 +413,22 @@ static int snd_pcm_dmix_start(snd_pcm_t *pcm)
        
        if (dmix->state != SND_PCM_STATE_PREPARED)
                return -EBADFD;
-       err = snd_timer_start(dmix->timer);
-       if (err < 0)
-               return err;
-       dmix->state = SND_PCM_STATE_RUNNING;
        snd_pcm_hwsync(dmix->spcm);
        dmix->slave_appl_ptr = dmix->slave_hw_ptr = *dmix->spcm->hw.ptr;
        avail = snd_pcm_mmap_playback_hw_avail(pcm);
-       if (avail < 0)
+       if (avail == 0)
+               dmix->state = STATE_RUN_PENDING;
+       else if (avail < 0)
                return 0;
-       if (avail > (snd_pcm_sframes_t)pcm->buffer_size)
-               avail = pcm->buffer_size;
-       snd_pcm_dmix_sync_area(pcm, avail);
+       else {
+               if (avail > (snd_pcm_sframes_t)pcm->buffer_size)
+                       avail = pcm->buffer_size;
+               err = snd_timer_start(dmix->timer);
+               if (err < 0)
+                       return err;
+               dmix->state = SND_PCM_STATE_RUNNING;
+               snd_pcm_dmix_sync_area(pcm, avail);
+       }
        gettimeofday(&tv, 0);
        dmix->trigger_tstamp.tv_sec = tv.tv_sec;
        dmix->trigger_tstamp.tv_nsec = tv.tv_usec * 1000L;
@@ -457,15 +475,19 @@ static int snd_pcm_dmix_pause(snd_pcm_t *pcm, int enable)
 {
        snd_pcm_direct_t *dmix = pcm->private_data;
         if (enable) {
-               if (dmix->state != SND_PCM_STATE_RUNNING)
+               if (dmix->state == SND_PCM_STATE_RUNNING)
+                       snd_timer_stop(dmix->timer);
+               else if (dmix->state != STATE_RUN_PENDING)
                        return -EBADFD;
                dmix->state = SND_PCM_STATE_PAUSED;
-               snd_timer_stop(dmix->timer);
        } else {
                if (dmix->state != SND_PCM_STATE_PAUSED)
                        return -EBADFD;
-                dmix->state = SND_PCM_STATE_RUNNING;
-                snd_timer_start(dmix->timer);
+               if (snd_pcm_mmap_playback_hw_avail(pcm) > 0) {
+                       dmix->state = SND_PCM_STATE_RUNNING;
+                       snd_timer_start(dmix->timer);
+               } else
+                       dmix->state = STATE_RUN_PENDING;
        }
        return 0;
 }
@@ -553,6 +575,12 @@ static snd_pcm_sframes_t snd_pcm_dmix_mmap_commit(snd_pcm_t *pcm,
                break;
        }
        snd_pcm_mmap_appl_forward(pcm, size);
+       if (dmix->state == STATE_RUN_PENDING) {
+               err = snd_timer_start(dmix->timer);
+               if (err < 0)
+                       return err;
+               dmix->state = SND_PCM_STATE_RUNNING;
+       }
        if (dmix->state == SND_PCM_STATE_RUNNING) {
                err = snd_pcm_dmix_sync_ptr(pcm);
                if (err < 0)