linux-kernel - Re: [PATCH v3 1/3] sched/core: Warn if cpumask has a mix of isolcpus and housekeeping CPUs

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Message-ID: <20181026083235.GW3109@worktop.c.hoisthospitality.com>
Date:   Fri, 26 Oct 2018 10:32:35 +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 1/3] sched/core: Warn if cpumask has a mix of isolcpus
 and housekeeping CPUs

On Fri, Oct 26, 2018 at 12:12:21AM +0530, Srikar Dronamraju wrote:
> @@ -4778,6 +4779,16 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
>  
>  	cpuset_cpus_allowed(p, cpus_allowed);
>  	cpumask_and(new_mask, in_mask, cpus_allowed);
> +	hk_mask = housekeeping_cpumask(HK_FLAG_DOMAIN);
> +
> +	/*
> +	 * Warn if the cpumask provided has CPUs that are part of isolated and
> +	 * housekeeping_cpumask
> +	 */
> +	if (!cpumask_subset(new_mask, hk_mask) &&
> +			cpumask_intersects(new_mask, hk_mask))
> +		pr_warn("pid %d: Mix of isolcpus and non-isolcpus provided\n",
> +			p->pid);
>  
>  	/*
>  	 * Since bandwidth control happens on root_domain basis,

That is horribly coding style, and completely pointless. Also user
trigerable printl like that should be rate limited at the very least.