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=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 A7ED6C433DF for ; Mon, 8 Jun 2020 13:02:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 80826206C3 for ; Mon, 8 Jun 2020 13:02:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729348AbgFHNCM (ORCPT ); Mon, 8 Jun 2020 09:02:12 -0400 Received: from mx2.suse.de ([195.135.220.15]:59490 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728245AbgFHNCM (ORCPT ); Mon, 8 Jun 2020 09:02:12 -0400 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=?= Cc: Jaroslav Kysela , Takashi Iwai , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org 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 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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