Re: [PATCH v2] cpuset: handle race between CPU hotplug and cpuset_hotplug_work

From	Tejun Heo <tj@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] cpuset: handle race between CPU hotplug and cpuset_hotplug_work
Date	2016-09-13 17:30 +0200
Message-ID	<sgXOO-3H6-3@gated-at.bofh.it> (permalink)
References	<sgqJb-6NI-3@gated-at.bofh.it> <sgqSR-6QP-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Sun, Sep 11, 2016 at 09:14:58PM -0700, Joonwoo Park wrote:
> A discrepancy between cpu_online_mask and cpuset's effective_cpus
> mask is inevitable during hotplug since cpuset defers updating of
> effective_cpus mask using a workqueue, during which time nothing
> prevents the system from more hotplug operations.  For that reason
> guarantee_online_cpus() walks up the cpuset hierarchy until it finds
> an intersection under the assumption that top cpuset's effective_cpus
> mask intersects with cpu_online_mask even with such a race occurring.
> 
> However a sequence of CPU hotplugs can open a time window, during which
> none of the effective CPUs in the top cpuset intersect with
> cpu_online_mask.

Applied to cgroup/for-4.8-fixes.

Thanks.

-- 
tejun

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Re: [PATCH] cpuset: handle race between CPU hotplug and  cpuset_hotplug_work Zefan Li <lizefan@huawei.com> - 2016-09-12 04:50 +0200
  Re: [PATCH] cpuset: handle race between CPU hotplug and  cpuset_hotplug_work Joonwoo Park <joonwoop@codeaurora.org> - 2016-09-12 06:10 +0200
    [PATCH v2] cpuset: handle race between CPU hotplug and cpuset_hotplug_work Joonwoo Park <joonwoop@codeaurora.org> - 2016-09-12 06:20 +0200
      Re: [PATCH v2] cpuset: handle race between CPU hotplug and  cpuset_hotplug_work Tejun Heo <tj@kernel.org> - 2016-09-13 17:30 +0200

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