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Date: Wed, 05 Mar 2014 17:10:01 -0800 From: Saravana Kannan <skannan@...eaurora.org> To: "Rafael J. Wysocki" <rjw@...ysocki.net> CC: Viresh Kumar <viresh.kumar@...aro.org>, linaro-kernel@...ts.linaro.org, cpufreq@...r.kernel.org, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com Subject: Re: [PATCH V2 3/3] cpufreq: initialize governor for a new policy under policy->rwsem 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 >>> >>> [<c0afe180>] (notifier_call_chain+0x40/0x68) from [<c02a23ac>] (__blocking_notifier_call_chain+0x40/0x58) >>> [<c02a23ac>] (__blocking_notifier_call_chain+0x40/0x58) from [<c02a23d8>] (blocking_notifier_call_chain+0x14/0x1c) >>> [<c02a23d8>] (blocking_notifier_call_chain+0x14/0x1c) from [<c0803c68>] (cpufreq_set_policy+0xd4/0x2b8) >>> [<c0803c68>] (cpufreq_set_policy+0xd4/0x2b8) from [<c0803e7c>] (cpufreq_init_policy+0x30/0x98) >>> [<c0803e7c>] (cpufreq_init_policy+0x30/0x98) from [<c0805a18>] (__cpufreq_add_dev.isra.17+0x4dc/0x7a4) >>> [<c0805a18>] (__cpufreq_add_dev.isra.17+0x4dc/0x7a4) from [<c0805d38>] (cpufreq_cpu_callback+0x58/0x84) >>> [<c0805d38>] (cpufreq_cpu_callback+0x58/0x84) from [<c0afe180>] (notifier_call_chain+0x40/0x68) >>> [<c0afe180>] (notifier_call_chain+0x40/0x68) from [<c02812dc>] (__cpu_notify+0x28/0x44) >>> [<c02812dc>] (__cpu_notify+0x28/0x44) from [<c0aeed90>] (_cpu_up+0xf4/0x1dc) >>> [<c0aeed90>] (_cpu_up+0xf4/0x1dc) from [<c0aeeed4>] (cpu_up+0x5c/0x78) >>> [<c0aeeed4>] (cpu_up+0x5c/0x78) from [<c0aec808>] (store_online+0x44/0x74) >>> [<c0aec808>] (store_online+0x44/0x74) from [<c03a40f4>] (sysfs_write_file+0x108/0x14c) >>> [<c03a40f4>] (sysfs_write_file+0x108/0x14c) from [<c03517d4>] (vfs_write+0xd0/0x180) >>> [<c03517d4>] (vfs_write+0xd0/0x180) from [<c0351ca8>] (SyS_write+0x38/0x68) >>> [<c0351ca8>] (SyS_write+0x38/0x68) from [<c0205de0>] (ret_fast_syscall+0x0/0x30) >>> >>> Fix these by taking locks at appropriate places in __cpufreq_add_dev() as well. >>> >>> Reported-by: Saravana Kannan <skannan@...eaurora.org> >>> Suggested-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com> >>> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org> >> >> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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