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>
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@ -375,17 +375,9 @@ struct dummy_hrtimer_pcm {
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ktime_t period_time;
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atomic_t running;
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struct hrtimer timer;
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struct tasklet_struct tasklet;
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struct snd_pcm_substream *substream;
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};
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static void dummy_hrtimer_pcm_elapsed(unsigned long priv)
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{
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struct dummy_hrtimer_pcm *dpcm = (struct dummy_hrtimer_pcm *)priv;
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if (atomic_read(&dpcm->running))
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snd_pcm_period_elapsed(dpcm->substream);
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}
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static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer)
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{
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struct dummy_hrtimer_pcm *dpcm;
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@ -393,7 +385,14 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer)
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dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer);
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if (!atomic_read(&dpcm->running))
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return HRTIMER_NORESTART;
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tasklet_schedule(&dpcm->tasklet);
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/*
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* In cases of XRUN and draining, this calls .trigger to stop PCM
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* substream.
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*/
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snd_pcm_period_elapsed(dpcm->substream);
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if (!atomic_read(&dpcm->running))
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return HRTIMER_NORESTART;
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hrtimer_forward_now(timer, dpcm->period_time);
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return HRTIMER_RESTART;
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}
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@ -403,7 +402,7 @@ static int dummy_hrtimer_start(struct snd_pcm_substream *substream)
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struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
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dpcm->base_time = hrtimer_cb_get_time(&dpcm->timer);
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hrtimer_start(&dpcm->timer, dpcm->period_time, HRTIMER_MODE_REL);
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hrtimer_start(&dpcm->timer, dpcm->period_time, HRTIMER_MODE_REL_SOFT);
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atomic_set(&dpcm->running, 1);
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return 0;
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}
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@ -413,14 +412,14 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream)
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struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
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atomic_set(&dpcm->running, 0);
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hrtimer_cancel(&dpcm->timer);
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if (!hrtimer_callback_running(&dpcm->timer))
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hrtimer_cancel(&dpcm->timer);
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return 0;
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}
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static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm)
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{
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hrtimer_cancel(&dpcm->timer);
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tasklet_kill(&dpcm->tasklet);
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}
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static snd_pcm_uframes_t
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@ -465,12 +464,10 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream)
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if (!dpcm)
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return -ENOMEM;
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substream->runtime->private_data = dpcm;
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hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);
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dpcm->timer.function = dummy_hrtimer_callback;
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dpcm->substream = substream;
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atomic_set(&dpcm->running, 0);
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tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed,
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(unsigned long)dpcm);
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return 0;
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}
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