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authorOmair Mohammed Abdullah <omair.m.abdullah@linux.intel.com>2012-09-29 12:24:05 +0530
committerBen Hutchings <ben@decadent.org.uk>2012-10-17 03:49:42 +0100
commit1fd7e28a2d9dec2c758bf43b92b1613dd22161d6 (patch)
tree8f3d0e78da1c2deb78b72ce99ec8c60474f685c9
parent7737238648b535686434fdb1717b10d4c4f7c6d8 (diff)
ALSA: aloop - add locking to timer access
commit d4f1e48bd11e3df6a26811f7a1f06c4225d92f7d upstream. When the loopback timer handler is running, calling del_timer() (for STOP trigger) will not wait for the handler to complete before deactivating the timer. The timer gets rescheduled in the handler as usual. Then a subsequent START trigger will try to start the timer using add_timer() with a timer pending leading to a kernel panic. Serialize the calls to add_timer() and del_timer() using a spin lock to avoid this. Signed-off-by: Omair Mohammed Abdullah <omair.m.abdullah@linux.intel.com> Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
-rw-r--r--sound/drivers/aloop.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index d83bafc5d8b5..193ce814c678 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -119,6 +119,7 @@ struct loopback_pcm {
unsigned int period_size_frac;
unsigned long last_jiffies;
struct timer_list timer;
+ spinlock_t timer_lock;
};
static struct platform_device *devices[SNDRV_CARDS];
@@ -169,6 +170,7 @@ static void loopback_timer_start(struct loopback_pcm *dpcm)
unsigned long tick;
unsigned int rate_shift = get_rate_shift(dpcm);
+ spin_lock(&dpcm->timer_lock);
if (rate_shift != dpcm->pcm_rate_shift) {
dpcm->pcm_rate_shift = rate_shift;
dpcm->period_size_frac = frac_pos(dpcm, dpcm->pcm_period_size);
@@ -181,12 +183,15 @@ static void loopback_timer_start(struct loopback_pcm *dpcm)
tick = (tick + dpcm->pcm_bps - 1) / dpcm->pcm_bps;
dpcm->timer.expires = jiffies + tick;
add_timer(&dpcm->timer);
+ spin_unlock(&dpcm->timer_lock);
}
static inline void loopback_timer_stop(struct loopback_pcm *dpcm)
{
+ spin_lock(&dpcm->timer_lock);
del_timer(&dpcm->timer);
dpcm->timer.expires = 0;
+ spin_unlock(&dpcm->timer_lock);
}
#define CABLE_VALID_PLAYBACK (1 << SNDRV_PCM_STREAM_PLAYBACK)
@@ -659,6 +664,7 @@ static int loopback_open(struct snd_pcm_substream *substream)
dpcm->substream = substream;
setup_timer(&dpcm->timer, loopback_timer_function,
(unsigned long)dpcm);
+ spin_lock_init(&dpcm->timer_lock);
cable = loopback->cables[substream->number][dev];
if (!cable) {