From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05F11C432C0 for ; Wed, 20 Nov 2019 15:23:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7BFF218AF for ; Wed, 20 Nov 2019 15:23:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728862AbfKTPXF (ORCPT ); Wed, 20 Nov 2019 10:23:05 -0500 Received: from esa1.mentor.iphmx.com ([68.232.129.153]:37646 "EHLO esa1.mentor.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727711AbfKTPXF (ORCPT ); Wed, 20 Nov 2019 10:23:05 -0500 IronPort-SDR: fS5WbXOWtL0bsb4i/Be4RcQmtbcbodvHkNJLMRfb/xdcc9gW27yhMh3J5rl4TI7ARju2zFlIK2 sc9xhWPYIPpjFYTFLFwyPnMBXVs8AcnOSQ5jyESjleoMqFKF9/PE6JIzRS3F5pYe3BBX5SSYox anwGLhLs5JybX5kkEaWVdXkY09HfRXs3vEUBGthVGVP4EvQ0ZsDKRfdJsEmKN1RItD6qw3xLUb KB8jI4Hf1mTTsYEuNXOg4fm/67cvs2XYOzieRH6NhmlFUYzSVvq+eV35lOxip+5cIUOOvo9o1s 4qQ= X-IronPort-AV: E=Sophos;i="5.69,222,1571731200"; d="scan'208";a="45218267" Received: from orw-gwy-02-in.mentorg.com ([192.94.38.167]) by esa1.mentor.iphmx.com with ESMTP; 20 Nov 2019 07:23:04 -0800 IronPort-SDR: bYPUGEGM4hJP9CtdKP9CCIzWMl698Oyf7D1zhUIBf56uhzsqjPnD0BOIjctfL/IsoHYuDC2lJE foyA1/d67rTQSxASd598Ot04ojSIrqksuB8E2NC4Zf4IpfJtyCwLtU42GeDXggeweSGPrxcDgL Gex3Ou1E6IR/SldgZ3xjtDampyz0V3TNQj1kQ52Nyvi9gLQb16gTjQguM5lPAIP2++/LiLTwWg s0nblBwuXD5KkipG0FwAhtWoN+6tS9Yt0XvKGVabvtCXj6k+ezySt/Jvd9kMf4pNGk9i0zfx/i D6I= From: Andrew Gabbasov To: 'Takashi Iwai' CC: , , Jaroslav Kysela , Takashi Iwai , Timo Wischer References: <20191120115856.4125-1-andrew_gabbasov@mentor.com> <20191120115856.4125-2-andrew_gabbasov@mentor.com> <20191120115856.4125-3-andrew_gabbasov@mentor.com> <20191120115856.4125-4-andrew_gabbasov@mentor.com> <20191120115856.4125-5-andrew_gabbasov@mentor.com> <20191120115856.4125-6-andrew_gabbasov@mentor.com> <20191120115856.4125-7-andrew_gabbasov@mentor.com> In-Reply-To: Subject: RE: [PATCH v4 6/7] ALSA: aloop: Support selection of snd_timer instead of jiffies Date: Wed, 20 Nov 2019 18:21:36 +0300 Organization: Mentor Graphics Corporation Message-ID: <000001d59fb6$4ca36aa0$e5ea3fe0$@mentor.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQHVn5oKhCAU3Kkkmk2hDkJrcybUyqeUH9gAgAAKtoA= Content-Language: en-us X-Originating-IP: [137.202.0.90] X-ClientProxiedBy: SVR-IES-MBX-07.mgc.mentorg.com (139.181.222.7) To svr-ies-mbx-02.mgc.mentorg.com (139.181.222.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Takashi, > -----Original Message----- > From: Takashi Iwai [mailto:tiwai@suse.de] > Sent: Wednesday, November 20, 2019 5:34 PM > To: Gabbasov, Andrew > Cc: alsa-devel@alsa-project.org; linux-kernel@vger.kernel.org; Jaroslav > Kysela; Takashi Iwai; Timo Wischer > Subject: Re: [PATCH v4 6/7] ALSA: aloop: Support selection of snd_timer > instead of jiffies > > On Wed, 20 Nov 2019 12:58:55 +0100, > Andrew Gabbasov wrote: > > +/* call in loopback->cable_lock */ > > +static int loopback_snd_timer_open(struct loopback_pcm *dpcm) > > +{ > > + int err = 0; > > + struct snd_timer_id tid = { > > + .dev_class = SNDRV_TIMER_CLASS_PCM, > > + .dev_sclass = SNDRV_TIMER_SCLASS_APPLICATION, > > + }; > > + struct snd_timer_instance *timeri; > > + struct loopback_cable *cable = dpcm->cable; > > + > > + spin_lock_irq(&cable->lock); > > + > > + /* check if timer was already opened. It is only opened once > > + * per playback and capture subdevice (aka cable). > > + */ > > + if (cable->snd_timer.instance) > > + goto unlock; > > + > > + err = loopback_parse_timer_id(dpcm->loopback->timer_source, &tid); > > + if (err < 0) { > > + pcm_err(dpcm->substream->pcm, > > + "Parsing timer source \'%s\' failed with %d", > > + dpcm->loopback->timer_source, err); > > + goto unlock; > > + } > > + > > + cable->snd_timer.stream = dpcm->substream->stream; > > + cable->snd_timer.id = tid; > > + > > + timeri = snd_timer_instance_new(dpcm->loopback->card->id); > > + if (!timeri) { > > + err = -ENOMEM; > > + goto unlock; > > + } > > + /* The callback has to be called from another tasklet. If > > + * SNDRV_TIMER_IFLG_FAST is specified it will be called from the > > + * snd_pcm_period_elapsed() call of the selected sound card. > > + * snd_pcm_period_elapsed() helds snd_pcm_stream_lock_irqsave(). > > + * Due to our callback loopback_snd_timer_function() also calls > > + * snd_pcm_period_elapsed() which calls > snd_pcm_stream_lock_irqsave(). > > + * This would end up in a dead lock. > > + */ > > + timeri->flags |= SNDRV_TIMER_IFLG_AUTO; > > + timeri->callback = loopback_snd_timer_function; > > + timeri->callback_data = (void *)cable; > > + timeri->ccallback = loopback_snd_timer_event; > > + > > + /* snd_timer_close() and snd_timer_open() should not be called with > > + * locked spinlock because both functions can block on a mutex. The > > + * mutex loopback->cable_lock is kept locked. Therefore > snd_timer_open() > > + * cannot be called a second time by the other device of the same > cable. > > + * Therefore the following issue cannot happen: > > + * [proc1] Call loopback_timer_open() -> > > + * Unlock cable->lock for snd_timer_close/open() call > > + * [proc2] Call loopback_timer_open() -> snd_timer_open(), > > + * snd_timer_start() > > + * [proc1] Call snd_timer_open() and overwrite running timer > > + * instance > > + */ > > + spin_unlock_irq(&cable->lock); > > + err = snd_timer_open(timeri, &cable->snd_timer.id, current->pid); > > + if (err < 0) { > > + pcm_err(dpcm->substream->pcm, > > + "snd_timer_open (%d,%d,%d) failed with %d", > > + cable->snd_timer.id.card, > > + cable->snd_timer.id.device, > > + cable->snd_timer.id.subdevice, > > + err); > > + snd_timer_instance_free(timeri); > > + return err; > > + } > > + spin_lock_irq(&cable->lock); > > + > > + cable->snd_timer.instance = timeri; > > + > > + /* initialise a tasklet used for draining */ > > + tasklet_init(&cable->snd_timer.event_tasklet, > > + loopback_snd_timer_tasklet, (unsigned long)timeri); > > This has to be set before snd_timer_open(). The callback might be > called immediately after snd_timer_open(). This tasklet is used/scheduled only in ccallback (not regular tick callback), and only for SNDRV_TIMER_EVENT_MSTOP event. Can this event really happen immediately after snd_timer_open()? Thanks! Best regards, Andrew