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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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Takashi 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: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.1
Thomas Gleixner 2017-12-21 11:42:03 +01:00 committed by Ingo Molnar
parent 42f42da41b
commit b03bbbe08f
1 changed files with 12 additions and 15 deletions
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27
sound/drivers/dummy.c
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@ -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;
}
@ -413,14 +412,14 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream)
struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0);
hrtimer_cancel(&dpcm->timer);
if (!hrtimer_callback_running(&dpcm->timer))
hrtimer_cancel(&dpcm->timer);
return 0;
}
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;
}