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ALSA: aloop - Fix possible IRQ lock inversion 

loopback_pos_update() can be called in the timer callback, thus the lock
held should be irq-safe.  Otherwise you'll get AB/BA deadlock together
with substream->self_group.lock.

Reported-and-tested-by: Knut Petersen <Knut_Petersen@t-online.de>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2011-03-18 07:31:53 +01:00
parent 5b7c757d1a
commit 98d21df431
1 changed files with 9 additions and 10 deletions
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19
sound/drivers/aloop.c
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@ -482,8 +482,9 @@ static unsigned int loopback_pos_update(struct loopback_cable *cable)
cable->streams[SNDRV_PCM_STREAM_CAPTURE];
unsigned long delta_play = 0, delta_capt = 0;
unsigned int running;
unsigned long flags;
spin_lock(&cable->lock);
spin_lock_irqsave(&cable->lock, flags);
running = cable->running ^ cable->pause;
if (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) {
delta_play = jiffies - dpcm_play->last_jiffies;
@ -495,10 +496,8 @@ static unsigned int loopback_pos_update(struct loopback_cable *cable)
dpcm_capt->last_jiffies += delta_capt;
}
if (delta_play == 0 && delta_capt == 0) {
spin_unlock(&cable->lock);
return running;
}
if (delta_play == 0 && delta_capt == 0)
goto unlock;
if (delta_play > delta_capt) {
loopback_bytepos_update(dpcm_play, delta_play - delta_capt,
@ -510,14 +509,14 @@ static unsigned int loopback_pos_update(struct loopback_cable *cable)
delta_capt = delta_play;
}
if (delta_play == 0 && delta_capt == 0) {
spin_unlock(&cable->lock);
return running;
}
if (delta_play == 0 && delta_capt == 0)
goto unlock;
/* 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);
unlock:
spin_unlock_irqrestore(&cable->lock, flags);
return running;
}