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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 01398C433E1 for ; Tue, 16 Jun 2020 16:01:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8C86214DB for ; Tue, 16 Jun 2020 16:01:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592323311; bh=QWZhGhZw6SXi3y7+QniH5c40RvMZkswOJ864wEI/Dn4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=bS1BF8xCPxxDLZRBXswl3SIRyITyjoc2YOrLefpVgQWJhaeKjb5t5x8a5hmEzvmMS 4+V7jQk4SzoGS+5zDxKOHOo+fa/DAj/iCfiu6Hs3oU5x9ND3lZF2DEGEUv3FLcg2kU DWr0U5b0F4b+1h6UN+u/4GP1VIo2x68Gw4z8geno= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733177AbgFPQBt (ORCPT ); Tue, 16 Jun 2020 12:01:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:48706 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732715AbgFPPvu (ORCPT ); Tue, 16 Jun 2020 11:51:50 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id ED9CE207C4; Tue, 16 Jun 2020 15:51:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592322709; bh=QWZhGhZw6SXi3y7+QniH5c40RvMZkswOJ864wEI/Dn4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gaff/vqBhlU7gjmeiE7KVO+oPHJeMzt1hob3HgW3cHIMwDPqUWh2QdOKX1A67zTuy gSoDrXYo4nCbUqMkCrIA/lckPX5BE20yljEWcAr98IkdfyK8ziyB/1MkqP52p7vCJe hveoLYRIpVfTOkI9KCfdJmvtFyLyB9xM0zkRRatk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= , Takashi Iwai Subject: [PATCH 5.6 074/161] ALSA: pcm: fix snd_pcm_link() lockdep splat Date: Tue, 16 Jun 2020 17:34:24 +0200 Message-Id: <20200616153109.904646314@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200616153106.402291280@linuxfoundation.org> References: <20200616153106.402291280@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 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 From: Michał Mirosław commit e18035cf5cb3d2bf8e4f4d350a23608bd208b934 upstream. 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 Link: https://lore.kernel.org/r/37252c65941e58473b1219ca9fab03d48f47e3e3.1591610330.git.mirq-linux@rere.qmqm.pl Signed-off-by: Greg Kroah-Hartman Signed-off-by: Takashi Iwai --- sound/core/pcm_native.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -138,6 +138,16 @@ void snd_pcm_stream_lock_irq(struct snd_ } EXPORT_SYMBOL_GPL(snd_pcm_stream_lock_irq); +static void snd_pcm_stream_lock_nested(struct snd_pcm_substream *substream) +{ + struct snd_pcm_group *group = &substream->self_group; + + if (substream->pcm->nonatomic) + mutex_lock_nested(&group->mutex, SINGLE_DEPTH_NESTING); + else + spin_lock_nested(&group->lock, SINGLE_DEPTH_NESTING); +} + /** * snd_pcm_stream_unlock_irq - Unlock the PCM stream * @substream: PCM substream @@ -2197,7 +2207,7 @@ static int snd_pcm_link(struct snd_pcm_s snd_pcm_stream_unlock_irq(substream); snd_pcm_group_lock_irq(target_group, nonatomic); - snd_pcm_stream_lock(substream1); + snd_pcm_stream_lock_nested(substream1); snd_pcm_group_assign(substream1, target_group); refcount_inc(&target_group->refs); snd_pcm_stream_unlock(substream1); @@ -2213,7 +2223,7 @@ static int snd_pcm_link(struct snd_pcm_s static void relink_to_local(struct snd_pcm_substream *substream) { - snd_pcm_stream_lock(substream); + snd_pcm_stream_lock_nested(substream); snd_pcm_group_assign(substream, &substream->self_group); snd_pcm_stream_unlock(substream); }