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=-10.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 A52D1C433E0 for ; Mon, 10 Aug 2020 20:09:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A32820838 for ; Mon, 10 Aug 2020 20:09:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=rere.qmqm.pl header.i=@rere.qmqm.pl header.b="YxjIiKkp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726515AbgHJUJY (ORCPT ); Mon, 10 Aug 2020 16:09:24 -0400 Received: from rere.qmqm.pl ([91.227.64.183]:39720 "EHLO rere.qmqm.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726111AbgHJUJX (ORCPT ); Mon, 10 Aug 2020 16:09:23 -0400 Received: from remote.user (localhost [127.0.0.1]) by rere.qmqm.pl (Postfix) with ESMTPSA id 4BQRrK1fWRz5m; Mon, 10 Aug 2020 22:09:21 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=rere.qmqm.pl; s=1; t=1597090161; bh=x2W1ts7k6Q36bs2XZvdlym6exqyAoh+vsYhpJCbyDaU=; h=Date:In-Reply-To:References:From:Subject:To:Cc:From; b=YxjIiKkp6ikJP1O/C4DC/cC5avVYsTqzIGXH+BSAc/cd7ZQp3/WRkB/dsFrQmXRgQ 4dBAr40teWQ4MtEcy4DRZ3q6asi1TeBdRQjKV+tI9FGf6VgN187Baco+mi9ADivpIx N9Fn4kwHACbkyaSagbXAJWM218+Nk4/2myrXfNjcwEmHUjCk338+YqkZbfZuf62OYG jJtxvPZhVeV3NMgF5VUHSU+WTbGe1CeIPsYN64kOtB5mfWV8o19I6nWT8tOfDE2/uG puDu6XkQHfov9dsOEtlbu51gbKn0y8t7bNz7NE7RqFV7Vq0ZP/Ps2s6VjtcswGLz1I 3vhfdhQan/TpA== X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.102.4 at mail Date: Mon, 10 Aug 2020 22:09:21 +0200 Message-Id: <501708a0f23b9d0a0dd63b38e03bf620f5018e35.1597089543.git.mirq-linux@rere.qmqm.pl> In-Reply-To: References: From: =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= Subject: [RFC PATCH 1/3] regulator: allocate memory outside of regulator_list mutex MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit To: Dmitry Osipenko Cc: Mark Brown , Liam Girdwood , linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Allocating memory with regulator_list_mutex held makes lockdep unhappy when memory pressure makes the system do fs_reclaim on eg. eMMC using a regulator. Push the lock inside regulator_init_coupling() after the allocation. ====================================================== WARNING: possible circular locking dependency detected 5.7.13+ #533 Not tainted ------------------------------------------------------ kswapd0/383 is trying to acquire lock: cca78ca4 (&sbi->write_io[i][j].io_rwsem){++++}-{3:3}, at: __submit_merged_write_cond+0x104/0x154 but task is already holding lock: c0e38518 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x0/0x50 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (fs_reclaim){+.+.}-{0:0}: fs_reclaim_acquire.part.11+0x40/0x50 fs_reclaim_acquire+0x24/0x28 __kmalloc+0x54/0x218 regulator_register+0x860/0x1584 dummy_regulator_probe+0x60/0xa8 [...] other info that might help us debug this: Chain exists of: &sbi->write_io[i][j].io_rwsem --> regulator_list_mutex --> fs_reclaim Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(regulator_list_mutex); lock(fs_reclaim); lock(&sbi->write_io[i][j].io_rwsem); *** DEADLOCK *** 1 lock held by kswapd0/383: #0: c0e38518 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x0/0x50 [...] Fixes: d8ca7d184b33 ("regulator: core: Introduce API for regulators coupling customization") Signed-off-by: Michał Mirosław --- drivers/regulator/core.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c index 2ee109950352..915a727d8fc7 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -4900,7 +4900,7 @@ static void regulator_remove_coupling(struct regulator_dev *rdev) static int regulator_init_coupling(struct regulator_dev *rdev) { struct regulator_dev **coupled; - int err, n_phandles; + int err = 0, n_phandles; if (!IS_ENABLED(CONFIG_OF)) n_phandles = 0; @@ -4911,6 +4911,7 @@ static int regulator_init_coupling(struct regulator_dev *rdev) if (!coupled) return -ENOMEM; + mutex_lock(®ulator_list_mutex); rdev->coupling_desc.coupled_rdevs = coupled; /* @@ -4923,19 +4924,21 @@ static int regulator_init_coupling(struct regulator_dev *rdev) /* regulator isn't coupled */ if (n_phandles == 0) - return 0; + goto out; - if (!of_check_coupling_data(rdev)) - return -EPERM; + if (!of_check_coupling_data(rdev)) { + err = -EPERM; + goto out; + } rdev->coupling_desc.coupler = regulator_find_coupler(rdev); if (IS_ERR(rdev->coupling_desc.coupler)) { err = PTR_ERR(rdev->coupling_desc.coupler); rdev_err(rdev, "failed to get coupler: %d\n", err); - return err; } - - return 0; +out: + mutex_unlock(®ulator_list_mutex); + return err; } static int generic_coupler_attach(struct regulator_coupler *coupler, @@ -5135,9 +5138,7 @@ regulator_register(const struct regulator_desc *regulator_desc, if (ret < 0) goto wash; - mutex_lock(®ulator_list_mutex); ret = regulator_init_coupling(rdev); - mutex_unlock(®ulator_list_mutex); if (ret < 0) goto wash; -- 2.20.1