ALSA: snd-aloop - fix locking issues (running flag updates)
On SMP machines, the cable->running update must be atomic, otherwise
stream is not started correctly sometimes.
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index 66786ea..38e8351 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -263,13 +263,17 @@
return err;
dpcm->last_jiffies = jiffies;
dpcm->pcm_rate_shift = 0;
- loopback_timer_start(dpcm);
+ spin_lock(&cable->lock);
cable->running |= (1 << substream->stream);
+ spin_unlock(&cable->lock);
+ loopback_timer_start(dpcm);
if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
loopback_active_notify(dpcm);
break;
case SNDRV_PCM_TRIGGER_STOP:
+ spin_lock(&cable->lock);
cable->running &= ~(1 << substream->stream);
+ spin_unlock(&cable->lock);
loopback_timer_stop(dpcm);
if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
loopback_active_notify(dpcm);
@@ -454,28 +458,30 @@
}
}
-static void loopback_pos_update(struct loopback_cable *cable)
+static unsigned int loopback_pos_update(struct loopback_cable *cable)
{
struct loopback_pcm *dpcm_play =
cable->streams[SNDRV_PCM_STREAM_PLAYBACK];
struct loopback_pcm *dpcm_capt =
cable->streams[SNDRV_PCM_STREAM_CAPTURE];
unsigned long delta_play = 0, delta_capt = 0;
+ unsigned int running;
spin_lock(&cable->lock);
- if (cable->running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) {
+ running = cable->running;
+ if (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) {
delta_play = jiffies - dpcm_play->last_jiffies;
dpcm_play->last_jiffies += delta_play;
}
- if (cable->running & (1 << SNDRV_PCM_STREAM_CAPTURE)) {
+ if (running & (1 << SNDRV_PCM_STREAM_CAPTURE)) {
delta_capt = jiffies - dpcm_capt->last_jiffies;
dpcm_capt->last_jiffies += delta_capt;
}
if (delta_play == 0 && delta_capt == 0) {
spin_unlock(&cable->lock);
- return;
+ return running;
}
if (delta_play > delta_capt) {
@@ -490,27 +496,27 @@
if (delta_play == 0 && delta_capt == 0) {
spin_unlock(&cable->lock);
- return;
+ return running;
}
/* note delta_capt == delta_play at this moment */
loopback_bytepos_update(dpcm_capt, delta_capt, BYTEPOS_UPDATE_COPY);
loopback_bytepos_update(dpcm_play, delta_play, BYTEPOS_UPDATE_POSONLY);
spin_unlock(&cable->lock);
+ return running;
}
static void loopback_timer_function(unsigned long data)
{
struct loopback_pcm *dpcm = (struct loopback_pcm *)data;
- int stream;
+ unsigned int running;
- loopback_pos_update(dpcm->cable);
- stream = dpcm->substream->stream;
- if (dpcm->cable->running & (1 << stream))
+ running = loopback_pos_update(dpcm->cable);
+ if (running & (1 << dpcm->substream->stream)) {
loopback_timer_start(dpcm);
- if (dpcm->period_update_pending) {
- dpcm->period_update_pending = 0;
- if (dpcm->cable->running & (1 << stream))
+ if (dpcm->period_update_pending) {
+ dpcm->period_update_pending = 0;
snd_pcm_period_elapsed(dpcm->substream);
+ }
}
}