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Commit b03bbbe0 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
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ALSA/dummy: Replace tasklet with softirq hrtimer 



The tasklet is used to defer the execution of snd_pcm_period_elapsed() to
the softirq context. Using the HRTIMER_MODE_SOFT mode invokes the timer
callback in softirq context as well which renders the tasklet useless.

[o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer]

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAnna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: default avatarTakashi Iwai <tiwai@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: alsa-devel@alsa-project.org
Cc: keescook@chromium.org
Link: http://lkml.kernel.org/r/20171221104205.7269-35-anna-maria@linutronix.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 42f42da4

sound/drivers/dummy.c

+12 −15
Original line number Diff line number Diff line
@@ -375,17 +375,9 @@ struct dummy_hrtimer_pcm { 
	ktime_t period_time;

	atomic_t running;

	struct hrtimer timer;

	struct tasklet_struct tasklet;

	struct snd_pcm_substream *substream;

};



static void dummy_hrtimer_pcm_elapsed(unsigned long priv)

{

	struct dummy_hrtimer_pcm *dpcm = (struct dummy_hrtimer_pcm *)priv;

	if (atomic_read(&dpcm->running))

		snd_pcm_period_elapsed(dpcm->substream);

}



static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer)

{

	struct dummy_hrtimer_pcm *dpcm;
@@ -393,7 +385,14 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) 
	dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer);

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

		return HRTIMER_NORESTART;

	tasklet_schedule(&dpcm->tasklet);

	/*

	 * In cases of XRUN and draining, this calls .trigger to stop PCM

	 * substream.

	 */

	snd_pcm_period_elapsed(dpcm->substream);

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

		return HRTIMER_NORESTART;



	hrtimer_forward_now(timer, dpcm->period_time);

	return HRTIMER_RESTART;

}
@@ -403,7 +402,7 @@ static int dummy_hrtimer_start(struct snd_pcm_substream *substream) 
	struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;



	dpcm->base_time = hrtimer_cb_get_time(&dpcm->timer);

	hrtimer_start(&dpcm->timer, dpcm->period_time, HRTIMER_MODE_REL);

	hrtimer_start(&dpcm->timer, dpcm->period_time, HRTIMER_MODE_REL_SOFT);

	atomic_set(&dpcm->running, 1);

	return 0;

}
@@ -413,6 +412,7 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) 
	struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;



	atomic_set(&dpcm->running, 0);

	if (!hrtimer_callback_running(&dpcm->timer))

		hrtimer_cancel(&dpcm->timer);

	return 0;

}
@@ -420,7 +420,6 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) 
static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm)

{

	hrtimer_cancel(&dpcm->timer);

	tasklet_kill(&dpcm->tasklet);

}



static snd_pcm_uframes_t
@@ -465,12 +464,10 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream) 
	if (!dpcm)

		return -ENOMEM;

	substream->runtime->private_data = dpcm;

	hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

	hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);

	dpcm->timer.function = dummy_hrtimer_callback;

	dpcm->substream = substream;

	atomic_set(&dpcm->running, 0);

	tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed,

		     (unsigned long)dpcm);

	return 0;

}