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Date:   Fri, 25 Oct 2019 17:52:25 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Christian Brauner <christian.brauner@ubuntu.com>
Cc:     Tejun Heo <tj@kernel.org>, dvyukov@google.com,
        Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        akpm@linux-foundation.org, arnd@arndb.de, deepa.kernel@gmail.com,
        ebiederm@xmission.com, elver@google.com, guro@fb.com,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        cgroups@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH cgroup/for-5.5] cgroup: remove
 cgroup_enable_task_cg_lists() optimization
Message-ID: <20191025155224.GC6020@redhat.com>
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On 10/25, Christian Brauner wrote:
>
> On Fri, Oct 25, 2019 at 04:13:25PM +0200, Oleg Nesterov wrote:
> > Almost every usage of task->flags (load or sore) can be reported as "da=
ta race".
> >=20
> > Say, you do
> >=20
> > =09if (task->flags & PF_KTHREAD)
> >=20
> > while this task does
> >=20
> > =09current->flags |=3D PF_FREEZER_SKIP;
> > =09schedule().
> >=20
> > this is data race.
>=20
> Right, but I thought we agreed on WONTFIX in those scenarios?
> The alternative is to READ_ONCE()/WRITE_ONCE() all of these.

Well, in my opinion this is WONTFIX, but I won't argue if someone
adds _ONCE to all of these. Same for task->state, exit_state, and
more.

Oleg.