linux-kernel - Re: [PATCH v7 08/22] cpuset: Don't use the cpu_possible

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Message-ID: <20210526160730.GC19691@willie-the-truck>
Date:   Wed, 26 May 2021 17:07:31 +0100
From:   Will Deacon <will@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Qais Yousef <qais.yousef@....com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Quentin Perret <qperret@...gle.com>, Tejun Heo <tj@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        kernel-team@...roid.com, Li Zefan <lizefan@...wei.com>
Subject: Re: [PATCH v7 08/22] cpuset: Don't use the cpu_possible_mask as a
 last resort for cgroup v1

On Wed, May 26, 2021 at 05:02:20PM +0200, Peter Zijlstra wrote:
> On Tue, May 25, 2021 at 04:14:18PM +0100, Will Deacon wrote:
> >  void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
> >  {
> > +	const struct cpumask *cs_mask;
> > +	const struct cpumask *possible_mask = task_cpu_possible_mask(tsk);
> > +
> >  	rcu_read_lock();
> > +	cs_mask = task_cs(tsk)->cpus_allowed;
> > +
> > +	if (!is_in_v2_mode() || !cpumask_subset(cs_mask, possible_mask))
> > +		goto unlock; /* select_fallback_rq will try harder */
> > +
> > +	do_set_cpus_allowed(tsk, cs_mask);
> > +unlock:
> 
> 	if (is_in_v2_mode() && cpumask_subset(cs_mask, possible_mask))
> 		do_set_cpus_allowed(tsk, cs_mask);
> 
> perhaps?

Absolutely.

Will