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From: Zhang Qiao <zhangqiao22@huawei.com>
To: Tejun Heo <tj@kernel.org>
Cc: <mingo@redhat.com>, <peterz@infradead.org>,
	<linux-kernel@vger.kernel.org>, <juri.lelli@redhat.com>,
	<vincent.guittot@linaro.org>, <dietmar.eggemann@arm.com>,
	<rostedt@goodmis.org>, <bsegall@google.com>, <mgorman@suse.de>,
	<bristot@redhat.com>
Subject: Re: [PATCH v2] kernel/sched: Fix sched_fork() access an invalid sched_task_group
Date: Tue, 14 Sep 2021 16:20:02 +0800	[thread overview]
Message-ID: <b30205b0-bf54-7255-fc1c-9dfa5dbb4940@huawei.com> (raw)
In-Reply-To: <YT+R3EnFgs78Vyvh@slm.duckdns.org>



在 2021/9/14 2:01, Tejun Heo 写道:
> Hello,
> 
> On Sat, Sep 11, 2021 at 03:50:54PM +0800, Zhang Qiao wrote:
>> Between cgroup_can_fork() and cgroup_post_fork(), the cgroup
>> membership is fixed and thus sched_task_group can't change. So
>> call sched_fork() after cgroup_can_fork() and update the child's
>> sched_task_group before it is used.
> 
> The part being fixed looks correct to me but it's difficult to for me to
> assess whether the whole relocation of the sched_fork() hook doesn't change

Indeed is this, although I checked and tested it many times.

> anything else. Besides, even if we decide to relocate the sched_fork hook, I
> think it'd be better to separate the two changes - one is a relatively safe
> bug fix, the other is a code reorganization with possibly subtle side
> effects. So, I think it'd be better to produce a patch which just fixes the
> bug even if that ends up introducing another function in the flow.

Perhaps we can fix this bug at sched_post_fork(), which is executed between cgroup_can_fork()
and cgroup_post_fork(). Relocate the fectching of task_group and access it at sched_post_fork().

thanks.

> 
> Thanks.
> 

  reply	other threads:[~2021-09-14  8:20 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-11  7:50 Zhang Qiao
2021-09-13 18:01 ` Tejun Heo
2021-09-14  8:20   ` Zhang Qiao [this message]
2021-09-14 16:23     ` Tejun Heo
2021-09-15  3:10       ` Zhang Qiao

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