linux-kernel - Re: [PATCH v3 2/3] sched/core: Don't mix isolcpus and housekeeping CPUs

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Date:   Fri, 26 Oct 2018 10:33:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wang <wang.yi59@....com.cn>, zhong.weidong@....com.cn,
        Yi Liu <liu.yi24@....com.cn>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH v3 2/3] sched/core: Don't mix isolcpus and housekeeping
 CPUs

On Fri, Oct 26, 2018 at 12:12:22AM +0530, Srikar Dronamraju wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 3064e0f..37e62b8 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1003,7 +1003,19 @@ static int migration_cpu_stop(void *data)
>   */
>  void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
>  {
> -	cpumask_copy(&p->cpus_allowed, new_mask);
> +	const struct cpumask *hk_mask = housekeeping_cpumask(HK_FLAG_DOMAIN);
> +
> +	/*
> +	 * If the cpumask provided has CPUs that are part of isolated and
> +	 * housekeeping_cpumask, then restrict it to just the CPUs that
> +	 * are part of the housekeeping_cpumask.
> +	 */
> +	if (!cpumask_subset(new_mask, hk_mask) &&
> +			cpumask_intersects(new_mask, hk_mask))
> +		cpumask_and(&p->cpus_allowed, new_mask, hk_mask);
> +	else
> +		cpumask_copy(&p->cpus_allowed, new_mask);
> +
>  	p->nr_cpus_allowed = cpumask_weight(new_mask);

NAK, I already explained that.