Commit fcfdebe7 authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: hrtimer - Fix lock-up 



The timer stop callback can be called from snd_timer_interrupt(), which
is called from the hrtimer callback.  Since hrtimer_cancel() waits for
the callback completion, this eventually results in a lock-up.

This patch fixes the problem by just toggling a flag at stop callback
and call hrtimer_cancel() later.

Reported-and-tested-by: default avatarWojtek Zabolotny <W.Zabolotny@elka.pw.edu.pl>
Cc: <stable@kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 5f60e496

sound/core/hrtimer.c

+13 −2
Original line number Diff line number Diff line
@@ -37,14 +37,22 @@ static unsigned int resolution; 
struct snd_hrtimer {

	struct snd_timer *timer;

	struct hrtimer hrt;

	atomic_t running;

};



static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)

{

	struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);

	struct snd_timer *t = stime->timer;



	if (!atomic_read(&stime->running))

		return HRTIMER_NORESTART;



	hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));

	snd_timer_interrupt(stime->timer, t->sticks);



	if (!atomic_read(&stime->running))

		return HRTIMER_NORESTART;

	return HRTIMER_RESTART;

}
@@ -58,6 +66,7 @@ static int snd_hrtimer_open(struct snd_timer *t) 
	hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

	stime->timer = t;

	stime->hrt.function = snd_hrtimer_callback;

	atomic_set(&stime->running, 0);

	t->private_data = stime;

	return 0;

}
@@ -78,16 +87,18 @@ static int snd_hrtimer_start(struct snd_timer *t) 
{

	struct snd_hrtimer *stime = t->private_data;



	atomic_set(&stime->running, 0);

	hrtimer_cancel(&stime->hrt);

	hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),

		      HRTIMER_MODE_REL);

	atomic_set(&stime->running, 1);

	return 0;

}



static int snd_hrtimer_stop(struct snd_timer *t)

{

	struct snd_hrtimer *stime = t->private_data;



	hrtimer_cancel(&stime->hrt);

	atomic_set(&stime->running, 0);

	return 0;

}

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