From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752352AbaBYIud (ORCPT ); Tue, 25 Feb 2014 03:50:33 -0500 Received: from mail-wg0-f44.google.com ([74.125.82.44]:51897 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752210AbaBYIua (ORCPT ); Tue, 25 Feb 2014 03:50:30 -0500 From: Viresh Kumar To: rjw@rjwysocki.net, skannan@codeaurora.org Cc: linaro-kernel@lists.linaro.org, cpufreq@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, Viresh Kumar Subject: [PATCH 3/3] cpufreq: initialize governor for a new policy under policy->rwsem Date: Tue, 25 Feb 2014 14:20:11 +0530 Message-Id: <3305df5abda26f22c501e5fa27ee7e2c8845b024.1393318100.git.viresh.kumar@linaro.org> X-Mailer: git-send-email 1.7.12.rc2.18.g61b472e In-Reply-To: <9f9546137135103556c69815c72b81ed93cc1ca2.1393318100.git.viresh.kumar@linaro.org> References: <9f9546137135103556c69815c72b81ed93cc1ca2.1393318100.git.viresh.kumar@linaro.org> In-Reply-To: <9f9546137135103556c69815c72b81ed93cc1ca2.1393318100.git.viresh.kumar@linaro.org> References: <9f9546137135103556c69815c72b81ed93cc1ca2.1393318100.git.viresh.kumar@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org policy->rwsem is used to lock access to all parts of code modifying struct cpufreq_policy but wasn't used on a new policy created from __cpufreq_add_dev(). Because of which if we call cpufreq_update_policy() repeatedly on one CPU and do offline/online of another CPU then we might see these crashes: Unable to handle kernel NULL pointer dereference at virtual address 00000020 pgd = c0003000 [00000020] *pgd=80000000004003, *pmd=00000000 Internal error: Oops: 206 [#1] PREEMPT SMP ARM PC is at __cpufreq_governor+0x10/0x1ac LR is at cpufreq_update_policy+0x114/0x150 ---[ end trace f23a8defea6cd706 ]--- Kernel panic - not syncing: Fatal exception CPU0: stopping CPU: 0 PID: 7136 Comm: mpdecision Tainted: G D W 3.10.0-gd727407-00074-g979ede8 #396 [] (notifier_call_chain+0x40/0x68) from [] (__blocking_notifier_call_chain+0x40/0x58) [] (__blocking_notifier_call_chain+0x40/0x58) from [] (blocking_notifier_call_chain+0x14/0x1c) [] (blocking_notifier_call_chain+0x14/0x1c) from [] (cpufreq_set_policy+0xd4/0x2b8) [] (cpufreq_set_policy+0xd4/0x2b8) from [] (cpufreq_init_policy+0x30/0x98) [] (cpufreq_init_policy+0x30/0x98) from [] (__cpufreq_add_dev.isra.17+0x4dc/0x7a4) [] (__cpufreq_add_dev.isra.17+0x4dc/0x7a4) from [] (cpufreq_cpu_callback+0x58/0x84) [] (cpufreq_cpu_callback+0x58/0x84) from [] (notifier_call_chain+0x40/0x68) [] (notifier_call_chain+0x40/0x68) from [] (__cpu_notify+0x28/0x44) [] (__cpu_notify+0x28/0x44) from [] (_cpu_up+0xf4/0x1dc) [] (_cpu_up+0xf4/0x1dc) from [] (cpu_up+0x5c/0x78) [] (cpu_up+0x5c/0x78) from [] (store_online+0x44/0x74) [] (store_online+0x44/0x74) from [] (sysfs_write_file+0x108/0x14c) [] (sysfs_write_file+0x108/0x14c) from [] (vfs_write+0xd0/0x180) [] (vfs_write+0xd0/0x180) from [] (SyS_write+0x38/0x68) [] (SyS_write+0x38/0x68) from [] (ret_fast_syscall+0x0/0x30) Fix these by taking locks at appropriate places in __cpufreq_add_dev() as well. Reported-by: Saravana Kannan Suggested-by: Srivatsa S. Bhat Signed-off-by: Viresh Kumar --- drivers/cpufreq/cpufreq.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 110c0cd..513d1d4 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1130,6 +1130,7 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif, policy->user_policy.max = policy->max; } + down_write(&policy->rwsem); write_lock_irqsave(&cpufreq_driver_lock, flags); for_each_cpu(j, policy->cpus) per_cpu(cpufreq_cpu_data, j) = policy; @@ -1204,6 +1205,7 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif, policy->user_policy.policy = policy->policy; policy->user_policy.governor = policy->governor; } + up_write(&policy->rwsem); kobject_uevent(&policy->kobj, KOBJ_ADD); up_read(&cpufreq_rwsem); -- 1.7.12.rc2.18.g61b472e