Messages in this thread Patch in this message | | | Date | Mon, 21 Mar 2011 16:07:02 -0700 | From | Greg KH <> | Subject | [63/87] ALSA: aloop - Fix possible IRQ lock inversion |
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2.6.37-stable review patch. If anyone has any objections, please let us know.
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From: Takashi Iwai <tiwai@suse.de>
commit 98d21df431ad55281e1abf780f8d51e3391900b2 upstream.
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> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- sound/drivers/aloop.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-)
--- a/sound/drivers/aloop.c +++ b/sound/drivers/aloop.c @@ -482,8 +482,9 @@ static unsigned int loopback_pos_update( 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( 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( 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; }
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