This is a note to let you know that I've just added the patch titled
ALSA: aloop - add locking to timer access
to the 3.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-aloop-add-locking-to-timer-access.patch
and it can be found in the queue-3.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From d4f1e48bd11e3df6a26811f7a1f06c4225d92f7d Mon Sep 17 00:00:00 2001
From: Omair Mohammed Abdullah <[email protected]>
Date: Sat, 29 Sep 2012 12:24:05 +0530
Subject: ALSA: aloop - add locking to timer access
From: Omair Mohammed Abdullah <[email protected]>
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 <[email protected]>
Signed-off-by: Vinod Koul <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
sound/drivers/aloop.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -120,6 +120,7 @@ struct loopback_pcm {
unsigned int last_drift;
unsigned long last_jiffies;
struct timer_list timer;
+ spinlock_t timer_lock;
};
static struct platform_device *devices[SNDRV_CARDS];
@@ -170,6 +171,7 @@ static void loopback_timer_start(struct
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);
@@ -182,12 +184,15 @@ static void loopback_timer_start(struct
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)
@@ -667,6 +672,7 @@ static int loopback_open(struct snd_pcm_
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) {
Patches currently in stable-queue which might be from
[email protected] are
queue-3.6/alsa-aloop-add-locking-to-timer-access.patch
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