From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751118AbdIFEaH (ORCPT ); Wed, 6 Sep 2017 00:30:07 -0400 Received: from smtp-proxy002.phy.lolipop.jp ([157.7.104.43]:53654 "EHLO smtp-proxy002.phy.lolipop.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750716AbdIFEaG (ORCPT ); Wed, 6 Sep 2017 00:30:06 -0400 Subject: Re: [PATCH 23/25 v3] ALSA/dummy: Replace tasklet with softirq hrtimer To: Sebastian Andrzej Siewior Cc: alsa-devel@alsa-project.org, keescook@chromium.org, Takashi Iwai , linux-kernel@vger.kernel.org, peterz@infradead.org, mingo@redhat.com, john.stultz@linaro.org, tglx@linutronix.de, anna-maria@linutronix.de, hch@lst.de References: <20170901102537.8066-1-o-takashi@sakamocchi.jp> <19775981-a3f2-5f65-e934-bfe25db62a43@sakamocchi.jp> <20170905155351.2xmwyxrirndfwtgo@breakpoint.cc> <4cf46286-daf8-d52c-dacc-fa16052dcdb2@sakamocchi.jp> <20170905161820.jtysvxtfleunbbmf@breakpoint.cc> From: Takashi Sakamoto Message-ID: <4d532df1-1581-f390-322d-39de5595d26f@sakamocchi.jp> Date: Wed, 6 Sep 2017 13:30:03 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170905161820.jtysvxtfleunbbmf@breakpoint.cc> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sep 6 2017 01:18, Sebastian Andrzej Siewior wrote: > From: Thomas Gleixner > > 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 > Signed-off-by: Anna-Maria Gleixner > Cc: Jaroslav Kysela > Cc: Takashi Iwai > Cc: Takashi Sakamoto > Cc: alsa-devel@alsa-project.org > [o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback > of hrtimer] > Signed-off-by: Takashi Sakamoto > Signed-off-by: Sebastian Andrzej Siewior > --- > On 2017-09-06 01:05:43 [+0900], Takashi Sakamoto wrote: >> As Iwai-san mentioned, in this function, .trigger can be called in two >> cases; XRUN occurs and draining is done. Thus, let you change the comment as >> 'In cases of XRUN and draining, this calls .trigger to stop PCM substream.'. >> I'm sorry to trouble you. >> >> snd_pcm_period_elapsed() >> ->snd_pcm_update_hw_ptr0() >> ->snd_pcm_update_state() >> ->snd_pcm_drain_done() >> ... >> ->.trigger(TRIGGER_STOP) >> ->xrun() >> ->snd_pcm_stop() >> ... >> ->.trigger(TRIGGER_STOP) >> > > I think you asked me just to update the comment. Did I do it right? > > v2…v3: updated the comment as per Takashi Sakamoto's suggestion. > v1…v2: merged Takashi Sakamoto fixup of the original patch into v2. > > sound/drivers/dummy.c | 25 +++++++++++-------------- > 1 file changed, 11 insertions(+), 14 deletions(-) This Looks good to me. I did quick test and confirmed that it brings no stalls. Tested-by: Takashi Sakamoto > diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c > index dd5ed037adf2..cdd851286f92 100644 > --- a/sound/drivers/dummy.c > +++ b/sound/drivers/dummy.c > @@ -376,17 +376,9 @@ 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; > @@ -394,7 +386,14 @@ 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; > } > @@ -414,14 +413,14 @@ 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 +465,10 @@ 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; > } Thanks Takashi Sakamoto