linux-kernel - Re: [PATCH v2 06/10] sched: Bypass bandwitdh checks with runtime disabled RT_GROUP

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Message-ID: <20250402120221.GI25239@noisy.programming.kicks-ass.net>
Date: Wed, 2 Apr 2025 14:02:21 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Michal Koutný <mkoutny@...e.com>
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Frederic Weisbecker <fweisbecker@...e.com>
Subject: Re: [PATCH v2 06/10] sched: Bypass bandwitdh checks with runtime
 disabled RT_GROUP_SCHED

On Mon, Mar 10, 2025 at 06:04:38PM +0100, Michal Koutný wrote:
> When RT_GROUPs are compiled but not exposed, their bandwidth cannot
> be configured (and it is not initialized for non-root task_groups neither).
> Therefore bypass any checks of task vs task_group bandwidth.
> 
> This will achieve behavior very similar to setups that have
> !CONFIG_RT_GROUP_SCHED and attach cpu controller to cgroup v2 hierarchy.
> (On a related note, this may allow having RT tasks with
> CONFIG_RT_GROUP_SCHED and cgroup v2 hierarchy.)

Can we make it so that cgroup-v2 is explicitly disallowed for now? As I
said earlier, we're looking at a new implemention with a incompatible
interface.