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=-3.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 17EB6C433DF for ; Mon, 8 Jun 2020 13:03:13 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 93FAA206C3 for ; Mon, 8 Jun 2020 13:03:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="TrElsSpn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 93FAA206C3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id 0E32F15E2; Mon, 8 Jun 2020 15:02:21 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 0E32F15E2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1591621391; bh=cngIIOD90DwKRQm8OFfM0qPCvKJ8YUNgXQlPiYnBJ0U=; h=Date:From:To:Subject:In-Reply-To:References:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=TrElsSpn+47rdQ1AjCEIBVI9rDILWX15vAwyNQb9YPduWqMKI47n27JB7BkRbPFH/ Rcvixv9IhJRtOYSGTno3ZXkV5Y1+tseUymyWqR+gaCj07JjGnp15FJcmGUTDHLa/Z3 RrmFMI5KcKnte0pnkSzwUNrqmSv9a7eLMBubUJPw= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id 99664F8021C; Mon, 8 Jun 2020 15:02:20 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 5CA8AF8021E; Mon, 8 Jun 2020 15:02:19 +0200 (CEST) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 813D3F80125 for ; Mon, 8 Jun 2020 15:02:11 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 813D3F80125 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id B0275AE8C; Mon, 8 Jun 2020 13:02:14 +0000 (UTC) Date: Mon, 08 Jun 2020 15:02:10 +0200 Message-ID: From: Takashi Iwai To: =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= Subject: Re: [PATCH 2/2] ALSA: pcm: fix snd_pcm_link() lockdep splat In-Reply-To: <37252c65941e58473b1219ca9fab03d48f47e3e3.1591610330.git.mirq-linux@rere.qmqm.pl> References: <37252c65941e58473b1219ca9fab03d48f47e3e3.1591610330.git.mirq-linux@rere.qmqm.pl> 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=UTF-8 Content-Transfer-Encoding: 8bit Cc: linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org, Takashi Iwai X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 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" On Mon, 08 Jun 2020 12:06:32 +0200, Michał Mirosław wrote: > > Add and use snd_pcm_stream_lock_nested() in snd_pcm_link/unlink > implementation. The code is fine, but generates a lockdep complaint: > > ============================================ > WARNING: possible recursive locking detected > 5.7.1mq+ #381 Tainted: G O > -------------------------------------------- > pulseaudio/4180 is trying to acquire lock: > ffff888402d6f508 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xda8/0xee0 [snd_pcm] > > but task is already holding lock: > ffff8883f7a8cf18 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xe4e/0xee0 [snd_pcm] > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&group->lock); > lock(&group->lock); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > 2 locks held by pulseaudio/4180: > #0: ffffffffa1a05190 (snd_pcm_link_rwsem){++++}-{3:3}, at: snd_pcm_common_ioctl+0xca0/0xee0 [snd_pcm] > #1: ffff8883f7a8cf18 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xe4e/0xee0 [snd_pcm] > [...] > > Cc: stable@vger.kernel.org > Fixes: f57f3df03a8e ("ALSA: pcm: More fine-grained PCM link locking") > Signed-off-by: Michał Mirosław Applied now. Thanks. Takashi