linux-kernel - Re: [PATCH v11 08/16] sched: Allow task CPU affinity to be restricted on asymmetric systems

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Date:   Wed, 18 Aug 2021 13:19:01 +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>,
        Valentin Schneider <valentin.schneider@....com>,
        Mark Rutland <mark.rutland@....com>, kernel-team@...roid.com
Subject: Re: [PATCH v11 08/16] sched: Allow task CPU affinity to be
 restricted on asymmetric systems

On Wed, Aug 18, 2021 at 01:53:28PM +0200, Peter Zijlstra wrote:
> On Wed, Aug 18, 2021 at 12:56:41PM +0200, Peter Zijlstra wrote:
> > On Wed, Aug 18, 2021 at 11:42:28AM +0100, Will Deacon wrote:
> 
> > > I think the idea looks good, but perhaps we could wrap things up a bit:
> > > 
> > > /* Comment about why this is useful with RT */
> > > static cpumask_t *clear_user_cpus_ptr(struct task_struct *p)
> > > {
> > > 	struct cpumask *user_mask = NULL;
> > > 
> > > 	swap(user_mask, p->user_cpus_ptr);
> > > 	return user_mask;
> > > }
> > > 
> > > void release_user_cpus_ptr(struct task_struct *p)
> > > {
> > > 	kfree(clear_user_cpus_ptr(p));
> > > }
> > > 
> > > Then just use clear_user_cpus_ptr() in sched/core.c where we know what
> > > we're doing (well, at least one of us does!).
> > 
> > OK, I'll go make it like that.
> 
> Something like so then?

Looks good to me, thanks!

Will