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 Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E8CE3C6FD1D for ; Tue, 21 Mar 2023 04:25:54 +0000 (UTC) Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id 6F25E1EF; Tue, 21 Mar 2023 05:25:01 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 6F25E1EF DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1679372751; bh=c+m+6s63SPq0G660YruIajDtnsqUjZPuQwL4lY1SAdM=; h=Date:From:To:Subject:References:In-Reply-To:List-Id:List-Archive: List-Help:List-Owner:List-Post:List-Subscribe:List-Unsubscribe: From; b=K5J8n/BnmWHw8SL6T+jeGQ6mgWNoxTPmv8i/5gPUEJNCHHAkIe73FAFk2eWUHuqDp Z3jhkYmTO7onxEYkX1mRwKE+ih06g45XWPnBfvzCCax30eytC5av/PruoZajJKNI5c 1rWM5ou627tInYorYXMWkElCfRsncOxr/GDjquUc= Received: from mailman-core.alsa-project.org (mailman-core.alsa-project.org [10.254.200.10]) by alsa1.perex.cz (Postfix) with ESMTP id C9EB9F8027B; Tue, 21 Mar 2023 05:24:39 +0100 (CET) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 1B915F8027B; Tue, 21 Mar 2023 05:24:08 +0100 (CET) Received: from wout2-smtp.messagingengine.com (wout2-smtp.messagingengine.com [64.147.123.25]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 60B43F80105 for ; Tue, 21 Mar 2023 05:23:53 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 60B43F80105 Authentication-Results: alsa1.perex.cz; dkim=pass (2048-bit key, unprotected) header.d=sakamocchi.jp header.i=@sakamocchi.jp header.a=rsa-sha256 header.s=fm2 header.b=Y05LcxB7; dkim=pass (2048-bit key, unprotected) header.d=messagingengine.com header.i=@messagingengine.com header.a=rsa-sha256 header.s=fm2 header.b=oSZK+W5c Received: from compute2.internal (compute2.nyi.internal [10.202.2.46]) by mailout.west.internal (Postfix) with ESMTP id 530B83200AAC; Tue, 21 Mar 2023 00:23:51 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute2.internal (MEProxy); Tue, 21 Mar 2023 00:23:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sakamocchi.jp; h=cc:content-type:content-type:date:date:from:from:in-reply-to :in-reply-to:message-id:mime-version:references:reply-to:sender :subject:subject:to:to; s=fm2; t=1679372630; x=1679459030; bh=xL GmrZ3DOIqIyKerLmV7JY4LZ459NQloUiyAwQYnAkI=; b=Y05LcxB7nmmBe7yYl4 rSJipRl8mf4U3VTkfn043LsZsNnZyfN+TgsZM9Hseaggd7sLDYVv+7HarLgyqSlv 736N/jjX2jkpZGu+6LbYMdW8jkxCxLXKPediZ0UcswKQZBLOW102ByeTk2hCNe1w CMG7plxiEXSjvytZ6eAfSAUgMXpLNITo7dtIN2GcqPZTI+TJeX+LaHV3I7yvWjMa xu8FKiviEh6b6E/KKq8OcWqrr4/RsU/WF2Gyik9+8Livyzv/80tNWRkC+opThdIZ MLriDhck8HVtOtJzJSPYeiOUtZjWjkGO3elxy9elYnkRBpYfWRyg+ZXi/XCsmW1Y 0kLg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:content-type:date:date :feedback-id:feedback-id:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:sender:subject :subject:to:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm2; t=1679372630; x=1679459030; bh=xLGmrZ3DOIqIy KerLmV7JY4LZ459NQloUiyAwQYnAkI=; b=oSZK+W5cJMuZ/QNCJOAsRPMZRgdxv /xIEpaQjCRFAtHWw95EhmfDyDkZ/WW0RgNLQKIVwDatJjvOkMvdI4tutd5w+a1oG 4Xv2HyOETQo/yRdB6ROAeamkfR4Ytg+ZJQr0hF8/tsskojm8nRf1eRIEc8lwBZy4 OfK4qx8X6v2fLgDEStE+PT875miSWCnqJkWa94vl+4s7vqyVzBwKyBf8KWWjLHrI w5YqAOp8Om5hPvQnwuKDevvodaDsZmE+uOceKd+XnOuUROxMtS9MfBPPyqkbMoLR KIL8f1tSjNR7ifxYP4Zo+pbYtsWRvVxy3jkr8ugyOtwKP/Zy+lD7ZX0Dg== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvhedrvdefledgieejucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvffukfhfgggtuggjsehttdertddttddvnecuhfhrohhmpefvrghkrghs hhhiucfurghkrghmohhtohcuoehoqdhtrghkrghshhhisehsrghkrghmohgttghhihdrjh hpqeenucggtffrrghtthgvrhhnpeejgeeifeeuveeufeeigeegjeelvdfgjeegffejgfdv keelhefgtdefteejleekjeenucffohhmrghinhepkhgvrhhnvghlrdhorhhgnecuvehluh hsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepohdqthgrkhgrshhh ihesshgrkhgrmhhotggthhhirdhjph X-ME-Proxy: Feedback-ID: ie8e14432:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 21 Mar 2023 00:23:49 -0400 (EDT) Date: Tue, 21 Mar 2023 13:23:47 +0900 From: Takashi Sakamoto To: Takashi Iwai , alsa-devel@alsa-project.org, John Keeping Subject: Re: [PATCH] ALSA: usb-audio: Fix recursive locking at XRUN during syncing Message-ID: <20230321042347.GA165562@workstation> Mail-Followup-To: Takashi Iwai , alsa-devel@alsa-project.org, John Keeping References: <20230320142838.494-1-tiwai@suse.de> <20230321040258.GA164337@workstation> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230321040258.GA164337@workstation> Message-ID-Hash: NMJFQAEILNJMNQIDPDNYC6CNTRQPS4JQ X-Message-ID-Hash: NMJFQAEILNJMNQIDPDNYC6CNTRQPS4JQ X-MailFrom: o-takashi@sakamocchi.jp X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-alsa-devel.alsa-project.org-0; header-match-alsa-devel.alsa-project.org-1; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Tue, Mar 21, 2023 at 01:02:58PM +0900, Takashi Sakamoto wrote: > Hi, > > On Mon, Mar 20, 2023 at 03:28:38PM +0100, Takashi Iwai wrote: > > The recent support of low latency playback in USB-audio driver made > > the snd_usb_queue_pending_output_urbs() function to be called via PCM > > ack ops. In the new code path, the function is performed alread in > > 's/alread/already/' or slang. > > > the PCM stream lock. The problem is that, when an XRUN is detected, > > the function calls snd_pcm_xrun() to notify, but snd_pcm_xrun() is > > 's/the function/the function/' > > > supposed to be called only outside the stream lock. As a result, it > > leads to a deadlock of PCM stream locking. > > > > For avoiding such a recursive locking, this patch adds an additional > > check to the code paths in PCM core that call the ack callback; now it > > checks the error code from the callback, and if it's -EPIPE, the XRUN > > is handled in the PCM core side gracefully. Along with it, the > > USB-audio driver code is changed to follow that, i.e. -EPIPE is > > returned instead of the explicit snd_pcm_xrun() call when the function > > is performed already in the stream lock. > > Practically, the implementation of 'pcm_hw' in alsa-lib never evaluates > the return value (see 'snd_pcm_hw_mmap_commit()' and the others). I guess > that it is inconvenient for the low-latency mode of USB Audio device class > driver for the case of failure. > > My additional concern is PCM indirect layer, since typically the layer > is used by drivers with SNDRV_PCM_INFO_SYNC_APPLPTR. But as long as I > read, the change does not matter to them. > > > Fixes: d5f871f89e21 ("ALSA: usb-audio: Improved lowlatency playback support") > > Reported-and-tested-by: John Keeping > > Link: https://lore.kernel.org/r/20230317195128.3911155-1-john@metanate.com > > Cc: Takashi Sakamoto > > Signed-off-by: Takashi Iwai > > --- > > sound/core/pcm_lib.c | 2 ++ > > sound/usb/endpoint.c | 22 ++++++++++++++-------- > > sound/usb/endpoint.h | 4 ++-- > > sound/usb/pcm.c | 2 +- > > 4 files changed, 19 insertions(+), 11 deletions(-) > > Anyway, John Keeping reports the change works well to solve the issue. I > have no objection to it. > > Reviewed-by; Takashi Sakamoto I forgot to mention that it is preferable to update 'ack callback' clause of API Documentation (i.e. writing-an-alsa-driver.rst) as well. > It is also convenient to IEC 61883-1/6 packet streaming engine for audio > and music unit in IEEE 1394 bus. I will post patches enough later for it. > > > diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c > > index 8b6aeb8a78f7..02fd65993e7e 100644 > > --- a/sound/core/pcm_lib.c > > +++ b/sound/core/pcm_lib.c > > @@ -2155,6 +2155,8 @@ int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream, > > ret = substream->ops->ack(substream); > > if (ret < 0) { > > runtime->control->appl_ptr = old_appl_ptr; > > + if (ret == -EPIPE) > > + __snd_pcm_xrun(substream); > > return ret; > > } > > } > > diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c > > index 419302e2057e..647fa054d8b1 100644 > > --- a/sound/usb/endpoint.c > > +++ b/sound/usb/endpoint.c > > @@ -455,8 +455,8 @@ static void push_back_to_ready_list(struct snd_usb_endpoint *ep, > > * This function is used both for implicit feedback endpoints and in low- > > * latency playback mode. > > */ > > -void snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep, > > - bool in_stream_lock) > > +int snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep, > > + bool in_stream_lock) > > { > > bool implicit_fb = snd_usb_endpoint_implicit_feedback_sink(ep); > > > > @@ -480,7 +480,7 @@ void snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep, > > spin_unlock_irqrestore(&ep->lock, flags); > > > > if (ctx == NULL) > > - return; > > + break; > > > > /* copy over the length information */ > > if (implicit_fb) { > > @@ -495,11 +495,14 @@ void snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep, > > break; > > if (err < 0) { > > /* push back to ready list again for -EAGAIN */ > > - if (err == -EAGAIN) > > + if (err == -EAGAIN) { > > push_back_to_ready_list(ep, ctx); > > - else > > + break; > > + } > > + > > + if (!in_stream_lock) > > notify_xrun(ep); > > - return; > > + return -EPIPE; > > } > > > > err = usb_submit_urb(ctx->urb, GFP_ATOMIC); > > @@ -507,13 +510,16 @@ void snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep, > > usb_audio_err(ep->chip, > > "Unable to submit urb #%d: %d at %s\n", > > ctx->index, err, __func__); > > - notify_xrun(ep); > > - return; > > + if (!in_stream_lock) > > + notify_xrun(ep); > > + return -EPIPE; > > } > > > > set_bit(ctx->index, &ep->active_mask); > > atomic_inc(&ep->submitted_urbs); > > } > > + > > + return 0; > > } > > > > /* > > diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h > > index 924f4351588c..c09f68ce08b1 100644 > > --- a/sound/usb/endpoint.h > > +++ b/sound/usb/endpoint.h > > @@ -52,7 +52,7 @@ int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep); > > int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep, > > struct snd_urb_ctx *ctx, int idx, > > unsigned int avail); > > -void snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep, > > - bool in_stream_lock); > > +int snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep, > > + bool in_stream_lock); > > > > #endif /* __USBAUDIO_ENDPOINT_H */ > > diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c > > index d959da7a1afb..eec5232f9fb2 100644 > > --- a/sound/usb/pcm.c > > +++ b/sound/usb/pcm.c > > @@ -1639,7 +1639,7 @@ static int snd_usb_pcm_playback_ack(struct snd_pcm_substream *substream) > > * outputs here > > */ > > if (!ep->active_mask) > > - snd_usb_queue_pending_output_urbs(ep, true); > > + return snd_usb_queue_pending_output_urbs(ep, true); > > return 0; > > } > > > > -- > > 2.35.3 > > > Thanks > > Takashi Sakamoto