From: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Frederic Weisbecker
<fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: Is not locking task_lock in cgroup_fork() safe?
Date: Mon, 8 Oct 2012 13:46:18 +0800 [thread overview]
Message-ID: <507268AA.8050509@huawei.com> (raw)
In-Reply-To: <20121008020138.GA4188@localhost>
On 2012/10/8 10:01, Tejun Heo wrote:
> On Mon, Oct 08, 2012 at 11:00:00AM +0900, Tejun Heo wrote:
>> 7e381b0eb1 ("cgroup: Drop task_lock(parent) on cgroup_fork()") removed
>> task_lock from cgroup_fork citing that current->cgroups can't change
>> due to threadgroup_change locking; however, threadgroup_change locking
>> is used only during CLONE_THREAD forking. If @current is forking a
>> new process, there's nothing preventing someone else to migrate the
>> parent while forking is in progress and delete the css_set it
>> currently is using. Am I confused somewhere?
You're right. threadgroup lock is held unconditionally in attach_task_py_pid(),
but it's held only for CLONE_THREAD in fork path, which I guess I overlooked
when reviewing the patch.
>
> Also, please note that task_lock is likely to be hot on local CPU at
> that point and avoiding it there might not really buy much.
>
Reverting that commit should be fine.
next prev parent reply other threads:[~2012-10-08 5:46 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-08 2:00 Is not locking task_lock in cgroup_fork() safe? Tejun Heo
2012-10-08 2:01 ` Tejun Heo
2012-10-08 5:46 ` Li Zefan [this message]
[not found] ` <507268AA.8050509-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2012-10-08 6:57 ` Tejun Heo
2012-10-08 6:57 ` Tejun Heo
2012-10-16 19:34 ` Tejun Heo
[not found] ` <20121016193428.GE16166-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-10-17 7:26 ` Li Zefan
2012-10-17 7:26 ` Li Zefan
2012-10-08 5:46 ` Li Zefan
2012-10-08 12:58 ` Frederic Weisbecker
2012-10-08 12:58 ` Frederic Weisbecker
2012-10-08 12:48 ` Frederic Weisbecker
[not found] ` <CAFTL4hzXWtzp7megsCAEuak5=_2SWmp9age-+wrpyQAU4BRZ0w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-10-16 19:33 ` Tejun Heo
[not found] ` <20121016193341.GD16166-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-10-18 14:50 ` Frederic Weisbecker
2012-10-18 14:50 ` Frederic Weisbecker
[not found] ` <CAFTL4hzo_w7HTgC9ApTk113X8WdZSpV+D+VSEe=604YEJFmKsg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-10-18 20:07 ` Tejun Heo
2012-10-18 20:07 ` Tejun Heo
[not found] ` <20121018200705.GG13370-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-10-18 20:53 ` Frederic Weisbecker
2012-10-18 20:53 ` Frederic Weisbecker
[not found] ` <CAFTL4hy7g4e11OUOyoihrEU8hiVgZoV1=141UtUpj9a72SNs_Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-10-19 0:38 ` Tejun Heo
2012-10-19 0:38 ` Tejun Heo
2012-10-19 0:38 ` Tejun Heo
[not found] ` <20121019003835.GE13370-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-10-19 0:58 ` Tejun Heo
2012-10-19 0:58 ` Tejun Heo
[not found] ` <20121019005801.GF13370-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-10-19 8:50 ` Li Zefan
2012-10-19 8:50 ` Li Zefan
2012-10-19 8:50 ` Li Zefan
2012-10-18 14:50 ` Frederic Weisbecker
2012-10-08 12:48 ` Frederic Weisbecker
2012-10-19 0:59 ` [PATCH cgroup/for-3.7-fixes 1/2] Revert "cgroup: Remove task_lock() from cgroup_post_fork()" Tejun Heo
[not found] ` <20121019005922.GG13370-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-10-19 8:51 ` Li Zefan
2012-10-19 13:35 ` Frederic Weisbecker
[not found] ` <CAFTL4hz82==b3ioSMhbKzh0CN1ivR7RQMKKMFFWu5PHPjg=Bfg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-10-19 19:38 ` Tejun Heo
[not found] ` <20121019193808.GL13370-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-10-19 19:44 ` Frederic Weisbecker
2012-10-19 19:44 ` Frederic Weisbecker
2012-10-19 19:44 ` Frederic Weisbecker
[not found] ` <CAFTL4hwQ6Ntn5GJwj=jiO2p3GdwhEMp0MyR8dgUj_Lx0U4kNqg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-10-19 21:07 ` Tejun Heo
2012-10-19 21:07 ` Tejun Heo
2012-10-19 21:07 ` Tejun Heo
[not found] ` <20121019210738.GA1180-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-10-20 18:21 ` Frederic Weisbecker
2012-10-20 18:21 ` Frederic Weisbecker
[not found] ` <CAFTL4hy+vrvJKrc1Y2FW44k=LBi72H=34337xALpbtG_3u5O7w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-10-20 18:23 ` Frederic Weisbecker
2012-10-20 18:23 ` Frederic Weisbecker
2012-10-20 22:37 ` Tejun Heo
2012-10-20 22:37 ` Tejun Heo
[not found] ` <20121020223709.GA5626-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2012-10-22 9:30 ` Frederic Weisbecker
2012-10-22 9:30 ` Frederic Weisbecker
2012-10-22 9:30 ` Frederic Weisbecker
2012-10-19 19:38 ` Tejun Heo
2012-10-19 13:35 ` Frederic Weisbecker
2012-10-19 0:59 ` Tejun Heo
2012-10-19 0:59 ` [PATCH cgroup/for-3.7-fixes 2/2] Revert "cgroup: Drop task_lock(parent) on cgroup_fork()" Tejun Heo
[not found] ` <20121019005951.GH13370-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-10-19 8:51 ` Li Zefan
2012-10-19 8:51 ` Li Zefan
2012-10-19 13:45 ` Frederic Weisbecker
2012-10-19 13:45 ` Frederic Weisbecker
2012-10-19 0:59 ` Tejun Heo
-- strict thread matches above, loose matches on Subject: below --
2012-10-08 2:00 Is not locking task_lock in cgroup_fork() safe? Tejun Heo
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