On Tue, 05 Sep 2017 17:53:51 +0200,
Sebastian Andrzej Siewior wrote:
>
> From: Thomas Gleixner <t...@linutronix.de>
>
> The tasklet is used to defer the execution of snd_pcm_period_elapsed() to
> the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer
> callback in softirq context as well which renders the tasklet useless.
>
> Signed-off-by: Thomas Gleixner <t...@linutronix.de>
> Signed-off-by: Anna-Maria Gleixner <anna-ma...@linutronix.de>
> Cc: Jaroslav Kysela <pe...@perex.cz>
> Cc: Takashi Iwai <ti...@suse.com>
> Cc: Takashi Sakamoto <o-taka...@sakamocchi.jp>
> Cc: alsa-de...@alsa-project.org
> [o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback
> of hrtimer]
> Signed-off-by: Takashi Sakamoto <o-taka...@sakamocchi.jp>
> Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
> ---
> On 2017-09-02 10:19:45 [+0900], Takashi Sakamoto wrote:
> > Yep. I request the authors to include this
> Thank you for providing a fix.
>
> v1…v2: merged Takashi Sakamoto fixup of the original patch into v2.
>
> So this patch now is okay?
Note that you can try it by yourself easily, as it's a dummy driver
that doesn't need anything special. Just run aplay for that device
(e.g. aplay -Dplughw:2 for card#2) can reproduce the original
problem.
> @@ -394,7 +386,12 @@ 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 a case of XRUN, this calls .trigger to stop PCM substream. */
As mentioned, the stop happens not only with XRUN but also in a normal
situation by draining.
Other than that, looks OK to me (but not tested it).
thanks,
Takashi
> + snd_pcm_period_elapsed(dpcm->substream);
> + if (!atomic_read(&dpcm->running))
> + return HRTIMER_NORESTART;
> +
> hrtimer_forward_now(timer, dpcm->period_time);
> return HRTIMER_RESTART;
> }
> @@ -414,14 +411,14 @@ 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
> @@ -466,12 +463,10 @@ 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_SOFT, HRTIMER_MODE_REL);
> 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;
> }
>
> --
> 2.14.1
>
