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Date:   Thu, 24 Oct 2019 10:54:27 -0700
From:   Tejun Heo <tj@kernel.org>
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        akpm@linux-foundation.org, arnd@arndb.de, christian@brauner.io,
        deepa.kernel@gmail.com, ebiederm@xmission.com, elver@google.com,
        guro@fb.com, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com
Subject: Re: cgroup_enable_task_cg_lists && PF_EXITING (Was: KCSAN: data-race
 in exit_signals / prepare_signal)
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 <20191021142111.GB1339@redhat.com>
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Hello, Oleg.

On Mon, Oct 21, 2019 at 04:21:11PM +0200, Oleg Nesterov wrote:
> could you explain the usage of siglock/PF_EXITING in
> cgroup_enable_task_cg_lists() ?
> 
> PF_EXITING is protected by cgroup_threadgroup_rwsem, not by
> sighand->siglock.

Yeah, the optimization was added a really long time ago and I'm not
sure it was ever correct.  I'm removing it.  If this ever becomes a
problem (pretty unlikely), I think the right thing to do is adding a
boot param instead of trying to do this dynamically.

Thanks.

-- 
tejun