From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Subject: Re: [RESEND PATCH v3] cpuset: restore sanity to
 cpuset_cpus_allowed_fallback()
Date: Wed, 12 Jun 2019 09:02:44 -0700
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To: Joel Savitz <jsavitz@redhat.com>
Cc: linux-kernel@vger.kernel.org, Li Zefan <lizefan@huawei.com>, Phil Auld <pauld@redhat.com>, Waiman Long <longman@redhat.com>, Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, cgroups@vger.kernel.org

On Wed, Jun 12, 2019 at 11:50:48AM -0400, Joel Savitz wrote:
> In the case that a process is constrained by taskset(1) (i.e.
> sched_setaffinity(2)) to a subset of available cpus, and all of those are
> subsequently offlined, the scheduler will set tsk->cpus_allowed to
> the current value of task_cs(tsk)->effective_cpus.
> 
> This is done via a call to do_set_cpus_allowed() in the context of 
> cpuset_cpus_allowed_fallback() made by the scheduler when this case is
> detected. This is the only call made to cpuset_cpus_allowed_fallback()
> in the latest mainline kernel.
> 
> However, this is not sane behavior.

While not perfect (we'll need to stop updating task's cpumask from
cpuset to make), this is still a signifcant improvement.

 Acked-by: Tejun Heo <tj@kernel.org>

If there's no objection, I'll route it through the cgroup tree.

Thanks.

-- 
tejun