linux-kernel - Re: [PATCH 5/6] sched/isolation: Introduce isolated task work

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Message-ID: <aHpYyZAprRjcqNTL@localhost.localdomain>
Date: Fri, 18 Jul 2025 16:23:05 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Valentin Schneider <vschneid@...hat.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Michal Hocko <mhocko@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org
Subject: Re: [PATCH 5/6] sched/isolation: Introduce isolated task work

Le Fri, Jul 18, 2025 at 11:52:01AM +0200, Valentin Schneider a écrit :
> On 03/07/25 16:07, Frederic Weisbecker wrote:
> > @@ -77,4 +77,21 @@ static inline bool cpu_is_isolated(int cpu)
> >              cpuset_cpu_is_isolated(cpu);
> >  }
> >
> > +#if defined(CONFIG_NO_HZ_FULL_WORK)
> > +extern int __isolated_task_work_queue(void);
> > +
> > +static inline int isolated_task_work_queue(void)
> > +{
> > +	if (!housekeeping_cpu(raw_smp_processor_id(), HK_TYPE_KERNEL_NOISE))
> > +		return -ENOTSUPP;
> > +
> 
> Am I being dense or this condition the opposite of what we want? That is,
> AIUI we want isolated_task_work() to run on NOHZ_FULL/isolated CPUs'
> resume-to-userspace path, so this should bail if the current CPU
> *is* a housekeeping CPU.

Geeze!

> 
> > +	return __isolated_task_work_queue();
> > +}
> > +
> 

-- 
Frederic Weisbecker
SUSE Labs