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From: Zhang Qiao <zhangqiao22@huawei.com>
To: Tejun Heo <tj@kernel.org>
Cc: <peterz@infradead.org>, <juri.lelli@redhat.com>,
	<linux-kernel@vger.kernel.org>, <mingo@redhat.com>,
	<vincent.guittot@linaro.org>
Subject: Re: [PATCH] kernel/sched: Fix sched_fork() access an invalid sched_task_group
Date: Wed, 1 Sep 2021 15:43:00 +0800	[thread overview]
Message-ID: <128d52ab-b4ee-65f8-e0a3-2796ef43a98b@huawei.com> (raw)
In-Reply-To: <YS60T2bfLpxb6SUY@slm.duckdns.org>


hello,tejun.

在 2021/9/1 6:59, Tejun Heo 写道:
> Hello,
> 
> On Tue, Aug 31, 2021 at 03:58:42PM +0800, Zhang Qiao wrote:
>>> I think this would allow cgroup migrations to take place before
>>> sched_post_fork() is run, which likely will break stuff. The right

cgroup migrations? Do you mean child process set its cgroups at
cgroup_subsys->fork()?

>>> thing to do likely is taking sched_task_group (and whatever other
>>> fields) after cgroup_can_fork(), which fixates the cgroup memberships,
>>
>> But it still seems possible that it accessed an invalid sched_task_group?
>> because the child process does not update its sched_task_group util
>> cgroup_post_fork().
> 
> Between cgroup_can_fork() and cgroup_post_fork(), the cgroup membership and
> thus sched_task_group can't change, so if the child sets it to the parent's
> inbetween, the sched_task_group can't go away.

so the child just need to update its sched_task_group after cgroup_can_fork(),
then call sched_fork(), is it right?

thanks.

--
Qiao Zhang.
> 
> Thanks.
> 

  reply	other threads:[~2021-09-01  7:43 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-26 11:26 Zhang Qiao
2021-08-30 11:49 ` Zhang Qiao
2021-08-30 14:39 ` Peter Zijlstra
2021-08-30 17:32   ` Tejun Heo
2021-08-31  7:58     ` Zhang Qiao
2021-08-31 22:59       ` Tejun Heo
2021-09-01  7:43         ` Zhang Qiao [this message]
2021-09-01 16:45           ` Tejun Heo
2021-09-02  7:42             ` Zhang Qiao
2021-09-07 17:01               ` Tejun Heo
2021-09-08 11:32                 ` Zhang Qiao
2021-09-08 16:29                   ` Tejun Heo
2021-09-09  9:45                     ` Zhang Qiao

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