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From: Tejun Heo <tj@kernel.org>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: cgroups@vger.kernel.org, alex.shi@linux.alibaba.com, guro@fb.com,
	hannes@cmpxchg.org, kernel-team@android.com,
	linger.lee@mediatek.com, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-mediatek@lists.infradead.org, lizefan@huawei.com,
	matthias.bgg@gmail.com, shuah@kernel.org, surenb@google.com,
	tomcherry@google.com
Subject: Re: [PATCH v2 1/3] cgroup: Iterate tasks that did not finish do_exit()
Date: Wed, 12 Feb 2020 17:03:06 -0500
Message-ID: <20200212220306.GH80993@mtj.thefacebook.com> (raw)
In-Reply-To: <20200124114017.8363-2-mkoutny@suse.com>

On Fri, Jan 24, 2020 at 12:40:15PM +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.
> 
> Reported-by: Suren Baghdasaryan <surenb@google.com>
> Fixes: c03cd7738a83 ("cgroup: Include dying leaders with live threads in PROCS iterations")
> Signed-off-by: Michal Koutný <mkoutny@suse.com>

Applied to cgroup/for-5.6-fixes.

Thanks.

-- 
tejun

  parent reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16  4:36 [PATCH 1/2] cgroup: allow deletion of cgroups containing only dying processes Suren Baghdasaryan
2020-01-16  4:36 ` [PATCH 2/2] kselftest/cgroup: add cgroup destruction test Suren Baghdasaryan
2020-01-17 15:15 ` [PATCH 0/3] cgroup: Iterate tasks that did not finish do_exit() Michal Koutný
2020-01-17 15:15   ` [PATCH 1/3] cgroup: Unify css_set task lists Michal Koutný
2020-01-17 16:59     ` Tejun Heo
2020-01-17 15:15   ` [PATCH 2/3] cgroup: Iterate tasks that did not finish do_exit() Michal Koutný
2020-01-17 17:28     ` Tejun Heo
2020-01-17 18:41       ` Suren Baghdasaryan
2020-01-20 14:56         ` Michal Koutný
2020-01-24 11:40           ` [PATCH v2 0/3] " Michal Koutný
2020-01-24 11:40             ` [PATCH v2 1/3] " Michal Koutný
2020-01-24 22:56               ` Suren Baghdasaryan
2020-02-05 17:27                 ` Suren Baghdasaryan
2020-02-12 22:03               ` Tejun Heo [this message]
2020-01-24 11:40             ` [PATCH v2 2/3] cgroup: Clean up css_set task traversal Michal Koutný
2020-01-24 11:40             ` [PATCH v2 3/3] kselftest/cgroup: add cgroup destruction test Michal Koutný
2020-02-12 22:10               ` Tejun Heo
2020-01-17 15:15   ` [PATCH " Michal Koutný
2020-01-17 17:30   ` [PATCH 0/3] cgroup: Iterate tasks that did not finish do_exit() Suren Baghdasaryan

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