From: Prateek Sood <prsood@codeaurora.org>
To: Waiman Long <longman@redhat.com>,
tj@kernel.org, lizefan@huawei.com, cgroups@vger.kernel.org,
mingo@kernel.org
Cc: linux-kernel@vger.kernel.org, sramana@codeaurora.org
Subject: Re: [PATCH] cgroup/cpuset: remove circular dependency deadlock
Date: Wed, 6 Sep 2017 19:53:59 +0530 [thread overview]
Message-ID: <0667dcec-ba42-5f44-596f-c2af891a770e@codeaurora.org> (raw)
In-Reply-To: <3992b0d5-947c-e343-5c07-8da43af5646d@redhat.com>
On 09/06/2017 06:26 PM, Waiman Long wrote:
> On 09/06/2017 07:48 AM, Prateek Sood wrote:
>> Remove circular dependency deadlock in a scenario where hotplug of CPU is
>> being done while there is updation in cgroup and cpuset triggered from
>> userspace.
>>
>> Example scenario:
>> kworker/0:0 => kthreadd => init:729 => init:1 => kworker/0:0
>>
>> kworker/0:0 - lock(cpuhotplug.mutex) [held]
>> flush(work) [no high prio workqueue available on CPU]
>> wait_for_completion()
>>
>> kthreadd - percpu_down_read(cgroup_threadgroup_rwsem) [waiting]
>>
>> init:729 - percpu_down_write(cgroup_threadgroup_rwsem) [held]
>> lock(cpuset_mutex) [waiting]
>>
>> init:1 - lock(cpuset_mutex) [held]
>> lock(cpuhotplug.mutex) [waiting]
>>
>> Eliminate this dependecy by reordering locking of cpuset_mutex
>> and cpuhotplug.mutex in following order
>> 1. Acquire cpuhotplug.mutex
>> 2. Acquire cpuset_mutex
>>
>> Signed-off-by: Prateek Sood <prsood@codeaurora.org>
>
> Is this patch for the latest upstream kernel or 4.4? There is no
> cpuhotplug.mutex anymore in upstream kernel. It is a per-cpu rwsem
> cpu_hotplug_lock.
>
> Cheers,
> Longman
>
Thanks for inputs, I will check latest kernel for details
Regards
Prateek
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation
Center, Inc., is a member of Code Aurora Forum, a Linux Foundation
Collaborative Project
next prev parent reply other threads:[~2017-09-06 14:24 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-06 11:48 [PATCH] cgroup/cpuset: remove circular dependency deadlock Prateek Sood
2017-09-06 12:56 ` Waiman Long
2017-09-06 14:23 ` Prateek Sood [this message]
2017-09-07 6:04 Prateek Sood
2017-09-07 7:28 ` Peter Zijlstra
2017-09-07 8:56 ` Boqun Feng
2017-09-07 9:07 ` Prateek Sood
2017-09-07 9:05 ` Prateek Sood
2017-09-07 13:56 Prateek Sood
2017-09-07 17:45 ` Peter Zijlstra
2017-09-08 2:13 ` Prateek Sood
2017-09-07 17:51 ` Peter Zijlstra
2017-10-09 13:27 ` Prateek Sood
2017-10-11 9:48 ` Peter Zijlstra
2017-10-25 8:39 ` Prateek Sood
2017-10-25 9:30 ` Peter Zijlstra
2017-10-26 11:52 ` Prateek Sood
2017-10-26 14:05 ` Waiman Long
2017-10-27 8:03 ` Prateek Sood
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