From: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: [PATCH 3/3] sched: Implement interface for cgroup unified
 hierarchy
Date: Thu, 17 Sep 2015 17:53:32 +0200
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To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, kernel-team <kernel-team-b10kYP2dOMg@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>

On Thu, Sep 17, 2015 at 11:52:45AM -0400, Tejun Heo wrote:
> Hello,
> 
> On Thu, Sep 17, 2015 at 05:10:49PM +0200, Peter Zijlstra wrote:
> > Subject: sched: Refuse to unplug a CPU if this will violate user task affinity
> > 
> > Its bad policy to allow unplugging a CPU for which a user set explicit
> > affinity, either strictly on this CPU or in case this was the last
> > online CPU in its mask.
> > 
> > Either would end up forcing the thread on a random other CPU, violating
> > the sys_sched_setaffinity() constraint.
> 
> Shouldn't this at least handle suspend differently?  Otherwise any
> userland task would be able to block suspend.

It does, it will allow suspend.