Date:   Wed, 1 Dec 2021 15:13:50 +0100
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Waiman Long <longman@redhat.com>
Cc:     Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Shuah Khan <shuah@kernel.org>, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kselftest@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <guro@fb.com>, Phil Auld <pauld@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Frederic Weisbecker <frederic@kernel.org>,
        Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v8 5/6] cgroup/cpuset: Update description of
 cpuset.cpus.partition in cgroup-v2.rst
Message-ID: <20211201141350.GA54766@blackbody.suse.cz>
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On Tue, Nov 30, 2021 at 10:56:34PM -0500, Waiman Long <longman@redhat.com> =
wrote:
> > >  =A0=A0 =A0A valid parent partition may distribute out all its CPUs to
> > >  =A0=A0 =A0its child partitions as long as it is not the root cgroup =
and
> > >  =A0=A0 =A0there is no task associated with it.
> > A valid parent partition which isn't root never has tasks in them to be=
gin
> > with.
> I believe there is some corner cases where it is possible to put task in =
an
> intermediate partition. That is why I put down this statement.

Just mind the threads -- cpuset controller is threaded and having tasks
in inner cgroup nodes is a real scenario. I wouldn't consider it a
corner case.

[ Actually, the paragraph could IMO be simplified:

> A valid parent partition may distribute out all its CPUs to
>=A0its child partitions as long as there is no task associated with it.

Assuming there's always at least one kernel thread in the root cgroup
that can't be migrated anyway.]


Michal

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