linux-kernel - Re: [PATCH 2/2] selftests/sched_ext: Add test to validate ops.dequeue() semantics

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Message-ID: <aYo_NsAkKvyMoXYv@slm.duckdns.org>
Date: Mon, 9 Feb 2026 10:10:30 -1000
From: Tejun Heo <tj@...nel.org>
To: Andrea Righi <arighi@...dia.com>
Cc: Emil Tsalapatis <emil@...alapatis.com>,
	David Vernet <void@...ifault.com>,
	Changwoo Min <changwoo@...lia.com>,
	Kuba Piecuch <jpiecuch@...gle.com>,
	Christian Loehle <christian.loehle@....com>,
	Daniel Hodges <hodgesd@...a.com>, sched-ext@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] selftests/sched_ext: Add test to validate
 ops.dequeue() semantics

Hello,

On Mon, Feb 09, 2026 at 08:17:24PM +0100, Andrea Righi wrote:
> Agreed. And just to be clear, for the purpose of triggering ops.dequeue(),
> **all** direct dispatches from ops.select_cpu() should be consistently
> ignored, including dispatches to user DSQs. I'll update this behavior in
> the next version, because this one treats direct dispatches to user DSQs
> from ops.select_cpu() as if the task is in the scheduler's custody, which
> shouldn't be the case for consistency.

I'm not sure about that. ops.select_cpu() doing direct dispatch is just a
shortcut and should be treated like the same operation being done at the
head of ops.enqueue(). That's what's happening semantically and I think we
should stick with what's happening underneath - ie. make ops.select_cpu()'s
shortcut the special case, not whether tasks in a user DSQ get ops.dequeue()
or not.

Thanks.

-- 
tejun