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From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <htejun@gmail.com>
Cc: rjw@sisk.pl, paul@paulmenage.org, lizf@cn.fujitsu.com,
	linux-pm@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org,
	containers@lists.linux-foundation.org, fweisbec@gmail.com,
	matthltc@us.ibm.com, akpm@linux-foundation.org,
	Tejun Heo <tj@kernel.org>, Paul Menage <menage@google.com>,
	Ben Blum <bblum@andrew.cmu.edu>
Subject: Re: [PATCH 3/4] threadgroup: extend threadgroup_lock() to cover exit and exec
Date: Sun, 18 Sep 2011 20:46:13 +0200	[thread overview]
Message-ID: <20110918184613.GA6159@redhat.com> (raw)
In-Reply-To: <20110918173723.GA2384@redhat.com>

On 09/18, Oleg Nesterov wrote:
>
> Of course I am in no position to ack the changes in this code, I do not
> fell I understand it enough. But afaics this series is fine.
  ^^^^
I do not feel ;)

> If I am right, afaics the only change 4/4 needs is that it should not add
> WARN_ON_ONCE(tsk->flags & PF_EXITING) into cgroup_task_migrate().

Hmm. Unless I missed something this WARN_ON_ONCE() is not right anyway,
because

> - * Call holding cgroup_mutex. May take task_lock of
> - * the task 'tsk' during call.
> + * Call with cgroup_mutex and threadgroup locked. May take task_lock of
> + * @tsk during call.
>   */
>  int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)

this is not true, cgroup_attach_proc() has other callers.

cgroup_attach_task_all() is probably fine, tsk should be current.

but cpuset_do_move_task() doesn't look fine at first glance, we can race
with the exiting task.

And this leads to another question about the cgroup_mutex/threadgroup_lock
nesting...

Oleg.


  reply	other threads:[~2011-09-18 18:50 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-04 18:01 [PATCHSET cgroup] extend threadgroup locking Tejun Heo
2011-09-04 18:01 ` [PATCH 1/4] cgroup: change locking order in attach_task_by_pid() Tejun Heo
2011-09-04 18:01 ` Tejun Heo
2011-09-18 18:56   ` Oleg Nesterov
2011-10-10 17:34     ` Tejun Heo
2011-10-10 17:43       ` Tejun Heo
2011-09-04 18:01 ` [PATCH 2/4] threadgroup: rename signal->threadgroup_fork_lock to ->group_rwsem Tejun Heo
2011-09-04 18:01 ` Tejun Heo
     [not found] ` <1315159280-25032-1-git-send-email-htejun-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2011-09-04 18:01   ` [PATCH 1/4] cgroup: change locking order in attach_task_by_pid() Tejun Heo
2011-09-04 18:01   ` [PATCH 2/4] threadgroup: rename signal->threadgroup_fork_lock to ->group_rwsem Tejun Heo
2011-09-04 18:01   ` [PATCH 3/4] threadgroup: extend threadgroup_lock() to cover exit and exec Tejun Heo
2011-09-04 18:01   ` [PATCH 4/4] cgroup: always lock threadgroup during migration Tejun Heo
2011-09-05  4:05   ` [PATCHSET cgroup] extend threadgroup locking Rafael J. Wysocki
2011-09-06  9:00   ` Li Zefan
2011-09-11  3:35   ` Tejun Heo
2011-09-04 18:01 ` [PATCH 3/4] threadgroup: extend threadgroup_lock() to cover exit and exec Tejun Heo
2011-09-04 18:01 ` Tejun Heo
2011-09-12  4:04   ` Paul Menage
2011-09-13  7:54     ` Tejun Heo
2011-09-18 17:37   ` Oleg Nesterov
2011-09-18 18:46     ` Oleg Nesterov [this message]
2011-10-08 18:37     ` Ben Blum
2011-10-10 17:11     ` Tejun Heo
2011-10-12 17:51       ` Oleg Nesterov
2011-10-12 18:05         ` Ben Blum
2011-10-12 18:29           ` Oleg Nesterov
2011-10-12 18:44             ` Ben Blum
2011-10-12 19:07               ` Oleg Nesterov
2011-09-04 18:01 ` [PATCH 4/4] cgroup: always lock threadgroup during migration Tejun Heo
2011-09-04 18:01 ` Tejun Heo
2011-09-18 17:41   ` Oleg Nesterov
2011-10-10 17:31     ` Tejun Heo
2011-09-05  4:05 ` [PATCHSET cgroup] extend threadgroup locking Rafael J. Wysocki
2011-09-05  4:05 ` Rafael J. Wysocki
2011-09-05  8:43   ` Tejun Heo
     [not found]   ` <201109050605.57360.rjw-KKrjLPT3xs0@public.gmane.org>
2011-09-05  8:43     ` Tejun Heo
2011-09-05  8:43   ` Tejun Heo
2011-09-06  9:00 ` Li Zefan
2011-09-06  9:00 ` Li Zefan
2011-09-11  3:35 ` Tejun Heo
2011-09-14 18:33   ` Oleg Nesterov
2011-09-14 23:33     ` Tejun Heo
2011-09-11  3:35 ` Tejun Heo
2011-09-12  4:11 ` Paul Menage

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