From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932618Ab0JHTta (ORCPT ); Fri, 8 Oct 2010 15:49:30 -0400 Received: from mail128.messagelabs.com ([216.82.250.131]:22412 "EHLO mail128.messagelabs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754651Ab0JHTta (ORCPT ); Fri, 8 Oct 2010 15:49:30 -0400 X-VirusChecked: Checked X-Env-Sender: jcarlyle@motorola.com X-Msg-Ref: server-4.tower-128.messagelabs.com!1286567368!35703548!1 X-StarScan-Version: 6.2.4; banners=-,-,- X-Originating-IP: [129.188.136.8] From: Jeffrey Carlyle To: Mark Brown , Liam Girdwood Cc: Lun Chang , , Jeffrey Carlyle Subject: [PATCH v2] regulator: avoid deadlock when disabling regulator with supply Date: Fri, 8 Oct 2010 14:49:19 -0500 Message-Id: <1286567360-11337-1-git-send-email-jeff.carlyle@motorola.com> X-Mailer: git-send-email 1.6.3.3 In-Reply-To: <20101008185739.GA6098@opensource.wolfsonmicro.com> References: <20101008185739.GA6098@opensource.wolfsonmicro.com> X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I have a regulator A that sets regulator B as its supply. When I call set_supply to add B as the supply for A, regulator A gets added to the supply_list for regulator B. When I call regulator_disable(A), I end up with a call chain like this: regulator_disable(A) > mutex_lock(A) > _regulator_disable(A) >> _regulator_disable(B) >>> _notifier_call_chain(B) >>>> mutex_lock(A) Which results in dead lock since we are trying to acquire the mutex lock for regulator A which we already hold. This patch addresses this issue by moving the call to disable regulator B outside of the lock aquired inside the initial call to regulator_disable. This change also addresses the issue of not acquiring the mutex for regulator B before calling _regulator_disable(B). Signed-off-by: Jeffrey Carlyle --- drivers/regulator/core.c | 35 ++++++++++++++++++++++++++--------- 1 files changed, 26 insertions(+), 9 deletions(-) diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c index cc8b337..2d215b5 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -63,7 +63,8 @@ struct regulator { }; static int _regulator_is_enabled(struct regulator_dev *rdev); -static int _regulator_disable(struct regulator_dev *rdev); +static int _regulator_disable(struct regulator_dev *rdev, + struct regulator_dev **supply_rdev_ptr); static int _regulator_get_voltage(struct regulator_dev *rdev); static int _regulator_get_current_limit(struct regulator_dev *rdev); static unsigned int _regulator_get_mode(struct regulator_dev *rdev); @@ -1348,7 +1349,8 @@ int regulator_enable(struct regulator *regulator) EXPORT_SYMBOL_GPL(regulator_enable); /* locks held by regulator_disable() */ -static int _regulator_disable(struct regulator_dev *rdev) +static int _regulator_disable(struct regulator_dev *rdev, + struct regulator_dev **supply_rdev_ptr) { int ret = 0; @@ -1376,8 +1378,7 @@ static int _regulator_disable(struct regulator_dev *rdev) } /* decrease our supplies ref count and disable if required */ - if (rdev->supply) - _regulator_disable(rdev->supply); + *supply_rdev_ptr = rdev->supply; rdev->use_count = 0; } else if (rdev->use_count > 1) { @@ -1407,17 +1408,29 @@ static int _regulator_disable(struct regulator_dev *rdev) int regulator_disable(struct regulator *regulator) { struct regulator_dev *rdev = regulator->rdev; + struct regulator_dev *supply_rdev = NULL; int ret = 0; mutex_lock(&rdev->mutex); - ret = _regulator_disable(rdev); + ret = _regulator_disable(rdev, &supply_rdev); mutex_unlock(&rdev->mutex); + + /* decrease our supplies ref count and disable if required */ + while (supply_rdev != NULL) { + rdev = supply_rdev; + + mutex_lock(&rdev->mutex); + _regulator_disable(rdev, &supply_rdev); + mutex_unlock(&rdev->mutex); + } + return ret; } EXPORT_SYMBOL_GPL(regulator_disable); /* locks held by regulator_force_disable() */ -static int _regulator_force_disable(struct regulator_dev *rdev) +static int _regulator_force_disable(struct regulator_dev *rdev, + struct regulator_dev **supply_rdev_ptr) { int ret = 0; @@ -1436,8 +1449,7 @@ static int _regulator_force_disable(struct regulator_dev *rdev) } /* decrease our supplies ref count and disable if required */ - if (rdev->supply) - _regulator_disable(rdev->supply); + *supply_rdev_ptr = rdev->supply; rdev->use_count = 0; return ret; @@ -1454,12 +1466,17 @@ static int _regulator_force_disable(struct regulator_dev *rdev) */ int regulator_force_disable(struct regulator *regulator) { + struct regulator_dev *supply_rdev = NULL; int ret; mutex_lock(®ulator->rdev->mutex); regulator->uA_load = 0; - ret = _regulator_force_disable(regulator->rdev); + ret = _regulator_force_disable(regulator->rdev, &supply_rdev); mutex_unlock(®ulator->rdev->mutex); + + if (supply_rdev) + regulator_disable(get_device_regulator(rdev_get_dev(supply_rdev))); + return ret; } EXPORT_SYMBOL_GPL(regulator_force_disable); -- 1.6.3.3