linux-kernel - Re: [PATCH 2/3] cgroup: Iterate tasks that did not finish do

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Message-ID: <CAJuCfpFqEUVFXsjD8XcCKsGXKTf72r0Ek5_1yqu_k5UZAssKTw@mail.gmail.com>
Date:   Fri, 17 Jan 2020 10:41:29 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Michal Koutný <mkoutny@...e.com>,
        cgroups mailinglist <cgroups@...r.kernel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Li Zefan <lizefan@...wei.com>, alex.shi@...ux.alibaba.com,
        Roman Gushchin <guro@...com>,
        kernel-team <kernel-team@...roid.com>,
        JeiFeng Lee <linger.lee@...iatek.com>,
        linux-arm-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        linux-kselftest@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, matthias.bgg@...il.com,
        shuah@...nel.org, Tom Cherry <tomcherry@...gle.com>
Subject: Re: [PATCH 2/3] cgroup: Iterate tasks that did not finish do_exit()

On Fri, Jan 17, 2020 at 9:28 AM Tejun Heo <tj@...nel.org> wrote:
>
> On Fri, Jan 17, 2020 at 04:15:32PM +0100, Michal Koutný wrote:
> > PF_EXITING is set earlier than actual removal from css_set when a task
> > is exitting. This can confuse cgroup.procs readers who see no PF_EXITING
> > tasks, however, rmdir is checking against css_set membership so it can
> > transitionally fail with EBUSY.
> >
> > Fix this by listing tasks that weren't unlinked from css_set active
> > lists.
> > It may happen that other users of the task iterator (without
> > CSS_TASK_ITER_PROCS) spot a PF_EXITING task before cgroup_exit(). This
> > is equal to the state before commit c03cd7738a83 ("cgroup: Include dying
> > leaders with live threads in PROCS iterations") but it may be reviewed
> > later.

Tested-by: Suren Baghdasaryan <surenb@...gle.com>

>
> Yeah, this looks fine to me.  Any chance you can order this before the
> clean up so that we can mark it for -stable.
>

+1 for reordering. Makes it easier to backport.
Thanks,
Suren.

> Thanks.
>
> --
> tejun
>
> --
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