From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH cgroup/for-5.5] cgroup: remove
 cgroup_enable_task_cg_lists() optimization
Date: Fri, 25 Oct 2019 17:52:25 +0200
Message-ID: <20191025155224.GC6020@redhat.com>
References: <0000000000003b1e8005956939f1@google.com>
 <20191021142111.GB1339@redhat.com>
 <20191024190351.GD3622521@devbig004.ftw2.facebook.com>
 <20191025125606.GI3622521@devbig004.ftw2.facebook.com>
 <20191025133358.pxpzxkhqc3mboi5x@wittgenstein>
 <20191025141325.GB6020@redhat.com>
 <20191025143224.wtwkkimqq4644iqq@wittgenstein>
Mime-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Return-path: <linux-kernel-owner@vger.kernel.org>
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;
        s=mimecast20190719; t=1572018756;
        h=from:from:reply-to:subject:subject:date:date:message-id:message-id:
         to:to:cc:cc:mime-version:mime-version:content-type:content-type:
         content-transfer-encoding:content-transfer-encoding:
         in-reply-to:in-reply-to:references:references;
        bh=F7ozuvXk8tbWjQzLtj2DAtfKZtAxllZ50ZDGOJC1UMA=;
        b=LMXmfIOEXDNypkNKKjtmUnCA4AMtml8tRbiROZ6IELmaqR6Y/enwUTxK7Mymn8HI+kflYY
        hIxjPm+azEj4P9q5nM8BUy8fjF3nIqLCMI4UTvLbFfYh23UAAIdb3dqhlJWRVpAj37GRw+
        fVOpXf95DOcWfHmI3IdcbWjyqDCNPsM=
In-Reply-To: <20191025143224.wtwkkimqq4644iqq@wittgenstein>
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <cgroups.vger.kernel.org>
Content-Type: text/plain; charset="us-ascii"
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

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.