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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 EE8F1C32771 for ; Thu, 9 Jan 2020 05:36:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7441206ED for ; Thu, 9 Jan 2020 05:36:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="huiN23DI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725932AbgAIFgf (ORCPT ); Thu, 9 Jan 2020 00:36:35 -0500 Received: from mail-il1-f194.google.com ([209.85.166.194]:38321 "EHLO mail-il1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725922AbgAIFgf (ORCPT ); Thu, 9 Jan 2020 00:36:35 -0500 Received: by mail-il1-f194.google.com with SMTP id f5so4703718ilq.5 for ; Wed, 08 Jan 2020 21:36:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=sAHhoFZ0iYCPxYt+rh/Px3+8GOp5DO3V29oeS42DXAM=; b=huiN23DIYcPHVv1KglkNFE9hwhktEqKgtWXiSkSJK5LmJDTbV3ps3AzdNKFwbVyRLU j6622puSU0EYgKiTBzKbjnldBj6p+SqrQ5IAZDpUi8Mwg/UESiWJuv042WLDon1jb0fb eG6eNsVZVo3F6z3ivbqJ842nbgPQHAGVoqVTN2RjedMNDHo32ifXrKlI4YvixtBl7NHU 2st3DsieNEM8T0b4/zNVLJJWvpkuCbrnmBaRNyYuw+F/Eviulg7v7aA8N2/pQkL2Ybet g/9n823BtG2EUxnmgbY6Vzbo5Id0yUpX+Kfy4DlJQVetjj4ZGHYyMnjKI3X+dy7LGIYJ LJyA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=sAHhoFZ0iYCPxYt+rh/Px3+8GOp5DO3V29oeS42DXAM=; b=RcDuhIBc0OWOpcF03yB7kh9nn+iDTDXmOTZYwWHAuQw5BXtiXE+R72TArOgnn6P72r PYpNH4QhbCFnKQydw+nwkHzzGjTCOYnrl0hmfJoNNzLdxV5Ozh0D86pzW/mdUYWucWVb siZB8b9CQ937cc+BExPyIgjt7kVRvjtTA+Cj18SwxpvQpCL2c1vNwhdF7cUxJuRn8cst 4vb2q1+Pn0PzpirBk6TLCAeywdGfw2tz0j2FAIOCiAp/XVq2MBxzRGaTyqLwEou53Hzo 4K8KhBeYEMfm12hCOyJM8HDKGtFAQ+FFBhe2uInZ0+Ey/D8xOGfkmaCzGUsjMcL4wqyp DGoA== X-Gm-Message-State: APjAAAXJJki9gmdIXcUW9ZFyvHkCe/YSHReGc0L5Pg4MTBmBrpChfl9R 5Ll7bqfGAQiKXc5EPy0TTZpvDpBAx8tceJVaWbiEt0PdiTw= X-Google-Smtp-Source: APXvYqzFc89SrQMcMWBXOOpciBA/UbRyMnmDTvKUFY09Y6diFKdpRQB/cIzzntYu/ZXrqm6Imlk1zgpmom3NbH7Nup8= X-Received: by 2002:a92:981b:: with SMTP id l27mr7483819ili.118.1578548194052; Wed, 08 Jan 2020 21:36:34 -0800 (PST) MIME-Version: 1.0 References: <20200108115007.31095-1-m.szyprowski@samsung.com> <20200108115007.31095-2-m.szyprowski@samsung.com> In-Reply-To: <20200108115007.31095-2-m.szyprowski@samsung.com> From: Tzung-Bi Shih Date: Thu, 9 Jan 2020 13:36:22 +0800 Message-ID: Subject: Re: [PATCH 2/2] ASoC: max98090: fix lockdep warning To: Marek Szyprowski Cc: ALSA development , Linux Kernel Mailing List , Linux Samsung SOC , Mark Brown , Sylwester Nawrocki , Dylan Reid , Jimmy Cheng-Yi Chiang , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz Content-Type: text/plain; charset="UTF-8" Sender: linux-samsung-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org On Wed, Jan 8, 2020 at 7:50 PM Marek Szyprowski wrote: > Fix this by introducing a separate mutex only for serializing the SHDN > hardware register related operations. This fix makes less sense to me. We used dapm_mutex intentionally because: both DAPM and userspace mixer control would change SHDN bit at the same time. > This fixes the following lockdep warning observed on Exynos4412-based > Odroid U3 board: > ====================================================== > WARNING: possible circular locking dependency detected > 5.5.0-rc5-next-20200107 #166 Not tainted > ------------------------------------------------------ > alsactl/1104 is trying to acquire lock: > ed0d50f4 (&card->dapm_mutex){+.+.}, at: max98090_shdn_save+0x1c/0x28 > > but task is already holding lock: > edb4b49c (&card->controls_rwsem){++++}, at: snd_ctl_ioctl+0xcc/0xbb8 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #1 (&card->controls_rwsem){++++}: > snd_ctl_add_replace+0x3c/0x84 > dapm_create_or_share_kcontrol+0x24c/0x2e0 > snd_soc_dapm_new_widgets+0x308/0x594 > snd_soc_bind_card+0x80c/0xad4 > devm_snd_soc_register_card+0x34/0x6c > odroid_audio_probe+0x288/0x34c > platform_drv_probe+0x6c/0xa4 > really_probe+0x200/0x490 > driver_probe_device+0x78/0x1f8 > bus_for_each_drv+0x74/0xb8 > __device_attach+0xd4/0x16c > bus_probe_device+0x88/0x90 > deferred_probe_work_func+0x3c/0xd0 > process_one_work+0x22c/0x7c4 > worker_thread+0x44/0x524 > kthread+0x130/0x164 > ret_from_fork+0x14/0x20 > 0x0 > > -> #0 (&card->dapm_mutex){+.+.}: > lock_acquire+0xe8/0x270 > __mutex_lock+0x9c/0xb18 > mutex_lock_nested+0x1c/0x24 > max98090_shdn_save+0x1c/0x28 > max98090_put_enum_double+0x20/0x40 > snd_ctl_ioctl+0x190/0xbb8 > ksys_ioctl+0x470/0xaf8 > ret_fast_syscall+0x0/0x28 > 0xbefaa564 As the stack trace suggested: when the card was still registering, alsactl can see the mixer control and try to change it. We have a discussion on an older thread (https://mailman.alsa-project.org/pipermail/alsa-devel/2019-December/160454.html). It is weird: userspace should not see things (e.g. no controlC0) until snd_card_register( ). I would like to spend some time to find the root cause. It would be a little challenging though (I have no real runtime to test...).