From mboxrd@z Thu Jan 1 00:00:00 1970 From: Saravana Kannan Subject: Re: [PATCH V2 3/3] cpufreq: initialize governor for a new policy under policy->rwsem Date: Wed, 05 Mar 2014 17:10:01 -0800 Message-ID: <5317CAE9.5090107@codeaurora.org> References: <98b7ae22d936456bf830aa749556a115969cfa47.1393904428.git.viresh.kumar@linaro.org> <2f6efe0c9058f64212ee220a1b386e04ba415686.1393904428.git.viresh.kumar@linaro.org> <1892466.Txf61ZRumM@vostro.rjw.lan> <1571634.sBIk9PhU1o@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp.codeaurora.org ([198.145.11.231]:57792 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754511AbaCFBKD (ORCPT ); Wed, 5 Mar 2014 20:10:03 -0500 In-Reply-To: <1571634.sBIk9PhU1o@vostro.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: Viresh Kumar , 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 On 03/05/2014 05:06 PM, Rafael J. Wysocki wrote: > On Thursday, March 06, 2014 02:04:39 AM Rafael J. Wysocki wrote: >> On Tuesday, March 04, 2014 11:44:01 AM Viresh Kumar wrote: >>> 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 >> >> I've rebased this one on top of 3.14-rc5 and queued it up for 3.14-rc6. >> >> Please check the bleeding-edge branch for the result. > > Actually, I think I'll queue up [2-3/3] for 3.14-rc6 instead. > Pretty close to having this tested and reported back. So, if you can wait, that would be better. Should probably see an email by Fri evening PST. -Saravana -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation