linux-kernel - Re: [PATCH] kernel/sched: Fix sched_fork() access an invalid sched_task

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Date:   Wed, 8 Sep 2021 06:29:38 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Zhang Qiao <zhangqiao22@...wei.com>
Cc:     linux-kernel@...r.kernel.org, juri.lelli@...hat.com,
        mingo@...hat.com, peterz@...radead.org, vincent.guittot@...aro.org
Subject: Re: [PATCH] kernel/sched: Fix sched_fork() access an invalid
 sched_task_group

Hello,

On Wed, Sep 08, 2021 at 07:32:06PM +0800, Zhang Qiao wrote:
> I will update this patch by following the steps below:
> 1)rename cgroup_subsys->fork() to cgroup_subsys->post_fork();
> 2)add cgroup_subsys->fork() and the cpu_cgroup_fork() callback like this:
> 
> void cpu_cgroup_fork(struct task_struct *task) {
> ....
> 	p->sched_task_group = task_group(current);
> 	__set_task_cpu(p, smp_processor_id());
> 	if (p->sched_class->task_fork)
> 		p->sched_class->task_fork(p);
> ....
> 
> 
> 3)call cgroup_subsys->fork() after cgroup_can_fork().
> 
> Do you have any suggestion?

I'm not following why it needs to shuffle the callbacks. Can't you just
relocate the fectching of task_group after can_fork?

Thanks.

-- 
tejun