Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d4f1e48b authored by Omair Mohammed Abdullah's avatar Omair Mohammed Abdullah Committed by Takashi Iwai
Browse files

ALSA: aloop - add locking to timer access 



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: default avatarOmair Mohammed Abdullah <omair.m.abdullah@linux.intel.com>
Signed-off-by: default avatarVinod Koul <vinod.koul@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent d17344b3

sound/drivers/aloop.c

+6 −0
Original line number Diff line number Diff line
@@ -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 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);
@@ -182,12 +184,15 @@ 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)
@@ -667,6 +672,7 @@ 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) {