From patchwork Sun Oct 22 21:40:12 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anna-Maria Behnsen X-Patchwork-Id: 10021811 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A140860224 for ; Sun, 22 Oct 2017 21:44:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 914D928477 for ; Sun, 22 Oct 2017 21:44:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8446728522; Sun, 22 Oct 2017 21:44:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.9 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_NONE autolearn=unavailable version=3.3.1 Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1DDCA28477 for ; Sun, 22 Oct 2017 21:44:08 +0000 (UTC) Received: from alsa0.perex.cz (localhost [127.0.0.1]) by alsa0.perex.cz (Postfix) with ESMTP id 895BC266E29; Sun, 22 Oct 2017 23:44:04 +0200 (CEST) X-Original-To: alsa-devel@alsa-project.org Delivered-To: alsa-devel@alsa-project.org Received: by alsa0.perex.cz (Postfix, from userid 1000) id 72E6D266E42; Sun, 22 Oct 2017 23:44:02 +0200 (CEST) Received: from Galois.linutronix.de (galois.linutronix.de [146.0.238.70]) by alsa0.perex.cz (Postfix) with ESMTP id 95D6E266D6B for ; Sun, 22 Oct 2017 23:43:59 +0200 (CEST) Received: from localhost ([127.0.0.1] helo=hypnos.tec.linutronix.de) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1e6O1e-0006VU-0v; Sun, 22 Oct 2017 23:43:18 +0200 Message-Id: <20171022214053.794128710@linutronix.de> User-Agent: quilt/0.63-1 Date: Sun, 22 Oct 2017 23:40:12 +0200 From: Anna-Maria Gleixner To: LKML References: <20171022213938.940451689@linutronix.de> MIME-Version: 1.0 Content-Disposition: inline; filename=ALSAdummy_Replace_tasklet_with_softirq_hrtimer.patch Cc: alsa-devel@alsa-project.org, keescook@chromium.org, Peter Zijlstra , Takashi Iwai , Ingo Molnar , John Stultz , Thomas Gleixner , Takashi Sakamoto , Christoph Hellwig Subject: [alsa-devel] [PATCH v2 34/37] ALSA/dummy: Replace tasklet with softirq hrtimer X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org X-Virus-Scanned: ClamAV using ClamSMTP From: Thomas Gleixner 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 Signed-off-by: Anna-Maria Gleixner Cc: Jaroslav Kysela Cc: Takashi Iwai Cc: Takashi Sakamoto Cc: alsa-devel@alsa-project.org Link: http://lkml.kernel.org/r/20170905161820.jtysvxtfleunbbmf@breakpoint.cc --- 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 | 27 ++++++++++++--------------- 1 file changed, 12 insertions(+), 15 deletions(-) --- 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_hrtime 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; } @@ -404,7 +403,7 @@ static int dummy_hrtimer_start(struct sn 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; } @@ -414,14 +413,14 @@ static int dummy_hrtimer_stop(struct snd 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 s 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; }