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

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Message-ID: <xhsmh1pqdg726.mognet@vschneid-thinkpadt14sgen2i.remote.csb>
Date: Fri, 18 Jul 2025 11:52:01 +0200
From: Valentin Schneider <vschneid@...hat.com>
To: Frederic Weisbecker <frederic@...nel.org>, LKML
 <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.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

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.

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