linux-kernel - Re: [PATCH v4 7/9] sched/fair: allow changing cgroup of new forked task

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Message-ID: <8a38c9aa-8404-e50a-58b1-7a87bf887d06@bytedance.com>
Date:   Tue, 16 Aug 2022 21:14:39 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     Tejun Heo <tj@...nel.org>, peterz@...radead.org,
        vincent.guittot@...aro.org, dietmar.eggemann@....com
Cc:     mingo@...hat.com, juri.lelli@...hat.com, rostedt@...dmis.org,
        bsegall@...gle.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 7/9] sched/fair: allow changing cgroup of new forked
 task

On 2022/8/16 05:11, Tejun Heo wrote:
> On Mon, Aug 08, 2022 at 08:57:43PM +0800, Chengming Zhou wrote:
>> commit 7dc603c9028e ("sched/fair: Fix PELT integrity for new tasks")
>> introduce a TASK_NEW state and an unnessary limitation that would fail
>> when changing cgroup of new forked task.
>>
>> Because at that time, we can't handle task_change_group_fair() for new
>> forked fair task which hasn't been woken up by wake_up_new_task(),
>> which will cause detach on an unattached task sched_avg problem.
>>
>> This patch delete this unnessary limitation by adding check before do
>> detach or attach in task_change_group_fair().
>>
>> So cpu_cgrp_subsys.can_attach() has nothing to do for fair tasks,
>> only define it in #ifdef CONFIG_RT_GROUP_SCHED.
>>
>> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
> 
> I don't know cfs enough to review this but it'd be really great to remove
> this restriction.

Thanks for your reply!

Friendly ping :-)