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=-3.8 required=3.0 tests=BAYES_00, 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 60D65C433E0 for ; Sun, 28 Feb 2021 11:33:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2CF1364E55 for ; Sun, 28 Feb 2021 11:33:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230414AbhB1Ldb (ORCPT ); Sun, 28 Feb 2021 06:33:31 -0500 Received: from mx2.suse.de ([195.135.220.15]:41400 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230045AbhB1Ld3 (ORCPT ); Sun, 28 Feb 2021 06:33:29 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id BAC12AAC5; Sun, 28 Feb 2021 11:32:46 +0000 (UTC) Date: Sun, 28 Feb 2021 12:32:46 +0100 Message-ID: From: Takashi Iwai To: Anton Yakovlev Cc: , , , "Michael S. Tsirkin" , Jaroslav Kysela , Takashi Iwai , Subject: Re: [PATCH v6 6/9] ALSA: virtio: PCM substream operators In-Reply-To: <20210227085956.1700687-7-anton.yakovlev@opensynergy.com> References: <20210227085956.1700687-1-anton.yakovlev@opensynergy.com> <20210227085956.1700687-7-anton.yakovlev@opensynergy.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 27 Feb 2021 09:59:53 +0100, Anton Yakovlev wrote: > > +static int virtsnd_pcm_trigger(struct snd_pcm_substream *substream, int command) > +{ > + struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream); > + struct virtio_snd *snd = vss->snd; > + struct virtio_snd_msg *msg; > + unsigned long flags; > + int rc; > + > + switch (command) { > + case SNDRV_PCM_TRIGGER_START: > + case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: { > + struct virtio_snd_queue *queue = virtsnd_pcm_queue(vss); > + > + spin_lock_irqsave(&queue->lock, flags); > + spin_lock(&vss->lock); > + rc = virtsnd_pcm_msg_send(vss); > + if (!rc) > + vss->xfer_enabled = true; > + spin_unlock(&vss->lock); > + spin_unlock_irqrestore(&queue->lock, flags); > + if (rc) > + return rc; > + > + msg = virtsnd_pcm_ctl_msg_alloc(vss, VIRTIO_SND_R_PCM_START, > + GFP_KERNEL); If we drop nonatomic PCM, this has to be changed: GFP_KERNEL is no longer valid in the trigger and the pointer callbacks. I wonder, though, the code below uses GFP_ATOMIC inconsistently... > + case SNDRV_PCM_TRIGGER_STOP: > + case SNDRV_PCM_TRIGGER_PAUSE_PUSH: { > + spin_lock_irqsave(&vss->lock, flags); > + vss->xfer_enabled = false; > + spin_unlock_irqrestore(&vss->lock, flags); > + > + /* > + * The substream needs to be released on the device side only > + * when it is completely stopped. > + */ > + vss->release = (command == SNDRV_PCM_TRIGGER_STOP); > + > + /* > + * The STOP command can be issued in an atomic context after > + * the drain is complete. Therefore, in general, we cannot sleep > + * here. > + */ > + msg = virtsnd_pcm_ctl_msg_alloc(vss, VIRTIO_SND_R_PCM_STOP, > + GFP_ATOMIC); BTW... > + default: { > + return -EINVAL; > + } Let's avoid braces inside the switch() unless it's inevitably needed. It makes the code harder to read. > +static snd_pcm_uframes_t > +virtsnd_pcm_pointer(struct snd_pcm_substream *substream) > +{ > + struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream); > + snd_pcm_uframes_t hw_ptr = SNDRV_PCM_POS_XRUN; > + unsigned long flags; > + > + spin_lock_irqsave(&vss->lock, flags); > + if (!vss->xfer_xrun) > + hw_ptr = bytes_to_frames(substream->runtime, vss->hw_ptr); > + spin_unlock_irqrestore(&vss->lock, flags); Oh, and if we drop nonatomc PCM, both trigger and pointer callbacks are guaranteed to be called inside the spinlock, hence you can remove *_irqsave() but just us spin_lock() in those two callbacks. thanks, Takashi