linux-kernel - Re: [PATCH 09/39] sched: Add @reason to sched_class->rq

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Message-ID: <20240624113212.GL31592@noisy.programming.kicks-ass.net>
Date: Mon, 24 Jun 2024 13:32:12 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Tejun Heo <tj@...nel.org>
Cc: torvalds@...ux-foundation.org, mingo@...hat.com, juri.lelli@...hat.com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
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	andrea.righi@...onical.com, joel@...lfernandes.org,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
	kernel-team@...a.com
Subject: Re: [PATCH 09/39] sched: Add @reason to
 sched_class->rq_{on|off}line()

On Wed, May 01, 2024 at 05:09:44AM -1000, Tejun Heo wrote:
> ->rq_{on|off}line are called either during CPU hotplug or cpuset partition
> updates. A planned BPF extensible sched_class wants to tell the BPF
> scheduler progs about CPU hotplug events in a way that's synchronized with
> rq state changes.
> 
> As the BPF scheduler progs aren't necessarily affected by cpuset partition
> updates, we need a way to distinguish the two types of events. Let's add an
> argument to tell them apart.

That would be a bug. Must not be able to ignore partitions.