linux-kernel - Re: [PATCH 01/15] sched/idle: Handle offlining first in idle loop

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Message-ID: <aW6ccexiQaPLQcS1@pavilion.home>
Date: Mon, 19 Jan 2026 22:04:49 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
	"Christophe Leroy (CS GROUP)" <chleroy@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Ben Segall <bsegall@...gle.com>, Boqun Feng <boqun.feng@...il.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
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	Xin Zhao <jackzxcui1989@....com>, linux-pm@...r.kernel.org,
	linux-s390@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 01/15] sched/idle: Handle offlining first in idle loop

Le Mon, Jan 19, 2026 at 01:53:47PM +0100, Peter Zijlstra a écrit :
> On Fri, Jan 16, 2026 at 03:51:54PM +0100, Frederic Weisbecker wrote:
> 
> >  kernel/sched/idle.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> > 
> > diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> > index c174afe1dd17..35d79af3286d 100644
> > --- a/kernel/sched/idle.c
> > +++ b/kernel/sched/idle.c
> > @@ -260,6 +260,12 @@ static void do_idle(void)
> >  {
> >  	int cpu = smp_processor_id();
> >  
> > +	if (cpu_is_offline(cpu)) {
> 
> Does it make sense to make that: if (unlikely(cpu_is_offline(cpu))) ?

Yes indeed!

> 
> > +		local_irq_disable();
> 
> Also, do we want something like:
> 
> 		WARN_ON_ONCE(need_resched());
> 
> ?

Definetly.

Thanks.

-- 
Frederic Weisbecker
SUSE Labs