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Date:   Tue, 4 Apr 2023 11:07:37 +0200
From:   Michal =?utf-8?Q?Koutn=C3=BD?= <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>,
        Christian Brauner <brauner@kernel.org>,
        cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
        Juri Lelli <juri.lelli@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        gscrivan@redhat.com
Subject: Re: [PATCH 3/3] cgroup/cpuset: Allow only one active attach
 operation per cpuset
Message-ID: <20230404090737.3g3uxga52bojgdu5@blackpad>
References: <20230331145045.2251683-1-longman@redhat.com>
 <20230331145045.2251683-4-longman@redhat.com>
 <20230403164736.lpjdpzxxnjlpxrqv@blackpad>
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Hi.

On Mon, Apr 03, 2023 at 01:41:33PM -0400, Waiman Long <longman@redhat.com> wrote:
> This patch is actually not related to the CLONE_INTO_GROUP problem in patch
> 1. It is a generic problem when multiple users are moving threads into
> cgroup.threads of the same or different cpusets simultaneously.

I meant this:
	__cgroup_procs_write
	  cgroup_kn_lock_live
	    mutex_lock(&cgroup_mutex)

and (more succintly)
	cgroup_update_dfl_csses
	  lockdep_assert_held(&cgroup_mutex)

Even the threaded migrations should be synchronized here.
Can you please explain in more detail what's the problematic case?

> I don't believe this patch has a dependency on patch 1.

(I meant the opposite, patch 1 would depend in this 3/3. But maybe this
one isn't need.)

Michal

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