Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Sender: Tejun Heo <htejun@gmail.com>
Date:   Mon, 13 Sep 2021 08:01:00 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Zhang Qiao <zhangqiao22@huawei.com>
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
Message-ID: <YT+R3EnFgs78Vyvh@slm.duckdns.org>
References: <20210911075054.6358-1-zhangqiao22@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20210911075054.6358-1-zhangqiao22@huawei.com>
Precedence: bulk

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
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.

Thanks.

-- 
tejun