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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260119125347.GT830755@noisy.programming.kicks-ass.net>
Date: Mon, 19 Jan 2026 13:53:47 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Frederic Weisbecker <frederic@...nel.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>,
	Heiko Carstens <hca@...ux.ibm.com>, Ingo Molnar <mingo@...hat.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Kieran Bingham <kbingham@...nel.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Mel Gorman <mgorman@...e.de>, Michael Ellerman <mpe@...erman.id.au>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Nicholas Piggin <npiggin@...il.com>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Uladzislau Rezki <urezki@...il.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	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

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))) ?

> +		local_irq_disable();

Also, do we want something like:

		WARN_ON_ONCE(need_resched());

?

> +		cpuhp_report_idle_dead();
> +		arch_cpu_idle_dead();
> +	}
> +
>  	/*
>  	 * Check if we need to update blocked load
>  	 */
> @@ -311,11 +317,6 @@ static void do_idle(void)
>  		 */
>  		local_irq_disable();
>  
> -		if (cpu_is_offline(cpu)) {
> -			cpuhp_report_idle_dead();
> -			arch_cpu_idle_dead();
> -		}
> -
>  		arch_cpu_idle_enter();
>  		rcu_nocb_flush_deferred_wakeup();
>  
> -- 
> 2.51.1
>