Re: [RFC][PATCH 7/9 v2] cgroup: avoid attaching task to a cgroup under rmdir()

[Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>]

On Fri, Apr 27, 2012 at 7:39 PM, Frederic Weisbecker <fweisbec@gmail.com> wrote:
> On Fri, Apr 27, 2012 at 03:02:22PM +0900, KAMEZAWA Hiroyuki wrote:
>> attach_task() is done under cgroup_mutex() but ->pre_destroy() callback
>> in rmdir() isn't called under cgroup_mutex().
>>
>> It's better to avoid attaching a task to a cgroup which
>> is under pre_destroy(). Considering memcg, the attached task may
>> increase resource usage after memcg's pre_destroy() confirms that
>> memcg is empty. This is not good.
>>
>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>> ---
>>  kernel/cgroup.c |    5 ++++-
>>  1 files changed, 4 insertions(+), 1 deletions(-)
>>
>> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
>> index ad8eae5..7a3076b 100644
>> --- a/kernel/cgroup.c
>> +++ b/kernel/cgroup.c
>> @@ -1953,6 +1953,9 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
>>       if (cgrp == oldcgrp)
>>               return 0;
>>
>> +     if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
>> +             return -EBUSY;
>> +
>
> You probably need to update cgroup_attach_proc() as well?
>
Ahh...I missed that. Thank you for pointing out !

Thanks,
-Kame

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