linux-kernel - Re: [PATCH 5/5] sched: Rework sched_class::wakeup_preempt() and rq_modified

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Message-ID: <20251128134427.GS4068168@noisy.programming.kicks-ass.net>
Date: Fri, 28 Nov 2025 14:44:27 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Kuba Piecuch <jpiecuch@...gle.com>
Cc: mingo@...nel.org, vincent.guittot@...aro.org,
	linux-kernel@...r.kernel.org, juri.lelli@...hat.com,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, tj@...nel.org,
	void@...ifault.com, arighi@...dia.com, changwoo@...lia.com,
	sched-ext@...ts.linux.dev
Subject: Re: [PATCH 5/5] sched: Rework sched_class::wakeup_preempt() and
 rq_modified_*()

On Fri, Nov 28, 2025 at 02:36:38PM +0100, Peter Zijlstra wrote:
> On Fri, Nov 28, 2025 at 01:26:30PM +0000, Kuba Piecuch wrote:
> > Hi Peter,
> > 
> > On Thu Nov 27, 2025 at 3:39 PM UTC, Peter Zijlstra wrote:
> > > Additionally have set_next_task() re-set the value to the current class.
> > 
> > I don't see this part reflected in the patch. Is something missing?
> 
> Hmm, that does appear to have gone walk-about :/

Aah, here:

@@ -6797,6 +6799,7 @@ static void __sched notrace __schedule(i
 pick_again:
        next = pick_next_task(rq, rq->donor, &rf);
        rq_set_donor(rq, next);
+       rq->next_class = next->sched_class;
        if (unlikely(task_is_blocked(next))) {
                next = find_proxy_task(rq, next, &rf);
                if (!next)

Will fix changelog. Had to do the above instead of set_next_task()
because if proxy stuff.