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Date:   Mon, 13 Jun 2022 19:55:49 +0200
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Tejun Heo <tj@kernel.org>
Cc:     Waiman Long <longman@redhat.com>,
        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 v11 7/8] cgroup/cpuset: Update description of
 cpuset.cpus.partition in cgroup-v2.rst
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On Mon, Jun 13, 2022 at 07:28:25AM -1000, Tejun Heo <tj@kernel.org> wrote:
> I see. Is this part even necessary? All the .cpus files of the siblings a=
re
> owned by the parent who's responsible for configuring both the mode that =
the
> cgroup subtree is gonna be in and their cpumasks.=20

Do you mean such an example:

    parent	cpuset.cpus=3DSET (root)	cpuset.cpus.partition=3Disolated=20
    `- child_1	cpuset.cpus=3Dpartition_of(SET) (root)	cpuset.cpus.partition=
=3Disolated
    `- ...
    `- child_n	cpuset.cpus=3Dpartition_of(SET) (root)	cpuset.cpus.partition=
=3Disolated
?

I don't think child_*/cpuset.cpus must be owned by root.
Actually, the root would only configure the parent, i.e.
parent/cpuset.cpus (whose changes would be disallowed to the
unprivileged tasks) and the distribution among siblings would up to the
whatever runs below.

> Given that all the other errors it can make are notified through
> "invalid (REASON)" in the mode file, wouldn't it fit better to notify
> cpus configuration error the same way too?

Do you suggest that a write into child_*/cpuset.cpus that'd not be
exclusive wrt a sibling would result in an error string in
parent/cpuset.cpus.partition?

Thanks,
Michal

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