linux-kernel - Re: [PATCH] sched/core: Report failed rt migrations to non-root cgroup without rt bandwidth under RT_GROUP

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Message-ID: <d7oxdqxfos3jiuoxckvth2hinhqks65exroxu2lipyopeuiz5c@v7jwxoltx7hf>
Date: Wed, 17 Sep 2025 11:37:37 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Aaron Tomlin <atomlin@...mlin.com>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com, 
	vincent.guittot@...aro.org, dietmar.eggemann@....com, rostedt@...dmis.org, 
	bsegall@...gle.com, mgorman@...e.de, vschneid@...hat.com, 
	shashank.mahadasyam@...y.com, longman@...hat.com, tj@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/core: Report failed rt migrations to non-root
 cgroup without rt bandwidth under RT_GROUP_SCHED

On Tue, Sep 16, 2025 at 12:57:04PM -0400, Aaron Tomlin <atomlin@...mlin.com> wrote:
> I see. If I understand correctly, in this context, are you suggesting to
> modify the identified task's scheduling class (e.g. to SCHED_NORMAL) so the
> CPU controller can be enabled?

So I'd primarily suggest you to disable CONFIG_RT_GROUP_SCHED. It seems
you ran into a situation where you have kernel with
CONFIG_RT_GROUP_SCHED but userspace that'd like to use cgroup v2 and
these two are known not get well along. (Alternatively, you may switch
userspace to v1 if you really really need RT groups.)

Michal

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