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Date:   Fri, 25 Oct 2019 05:56:06 -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,
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        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
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 <20191021142111.GB1339@redhat.com>
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On Thu, Oct 24, 2019 at 12:03:51PM -0700, Tejun Heo wrote:
> cgroup_enable_task_cg_lists() is used to lazyily initialize task
> cgroup associations on the first use to reduce fork / exit overheads
> on systems which don't use cgroup.  Unfortunately, locking around it
> has never been actually correct and its value is dubious given how the
> vast majority of systems use cgroup right away from boot.
> 
> This patch removes the optimization.  For now, replace the cg_list
> based branches with WARN_ON_ONCE()'s to be on the safe side.  We can
> simplify the logic further in the future.
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Reported-by: Oleg Nesterov <oleg@redhat.com>

Applying to cgroup/for-5.5.

Thanks.

-- 
tejun