linux-kernel - Re: [PATCH 05/12] sched: Move sched_class::prio

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Message-ID: <20260113115622.GA831285@noisy.programming.kicks-ass.net>
Date: Tue, 13 Jan 2026 12:56:22 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: K Prateek Nayak <kprateek.nayak@....com>
Cc: Pierre Gondois <pierre.gondois@....com>, tj@...nel.org,
	linux-kernel@...r.kernel.org, mingo@...nel.org,
	juri.lelli@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, longman@...hat.com,
	hannes@...xchg.org, mkoutny@...e.com, void@...ifault.com,
	arighi@...dia.com, changwoo@...lia.com, cgroups@...r.kernel.org,
	sched-ext@...ts.linux.dev, liuwenfang@...or.com, tglx@...utronix.de,
	Christian Loehle <christian.loehle@....com>
Subject: Re: [PATCH 05/12] sched: Move sched_class::prio_changed() into the
 change pattern

On Tue, Jan 13, 2026 at 12:53:09PM +0100, Peter Zijlstra wrote:
> On Tue, Jan 13, 2026 at 04:35:02PM +0530, K Prateek Nayak wrote:
> 
> > Does enabling WARN_DOUBLE_CLOCK warn of a double clock update before
> > hitting this warning?
> 
> setup_new_dl_entity() -> update_rq_clock() seems like it will trip that
> in this case.

Something like so to fix: 9f239df55546 ("sched/deadline: Initialize dl_servers after SMP")


--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -752,8 +752,6 @@ static inline void setup_new_dl_entity(s
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 	struct rq *rq = rq_of_dl_rq(dl_rq);
 
-	update_rq_clock(rq);
-
 	WARN_ON(is_dl_boosted(dl_se));
 	WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
 
@@ -1834,6 +1832,7 @@ void sched_init_dl_servers(void)
 		rq = cpu_rq(cpu);
 
 		guard(rq_lock_irq)(rq);
+		update_rq_clock(rq);
 
 		dl_se = &rq->fair_server;