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>

1 files changed, 9 insertions, 10 deletions

diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index 12b44b0b677..a0da7755fce 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -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;
 }