linux-kernel - Re: [PATCH v3 18/19] x86/resctrl: Add cpu offline callback for resctrl work

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Date:   Wed, 5 Apr 2023 16:48:37 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     James Morse <james.morse@....com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        <shameerali.kolothum.thodi@...wei.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        <carl@...amperecomputing.com>, <lcherian@...vell.com>,
        <bobo.shaobowang@...wei.com>, <tan.shaopeng@...itsu.com>,
        <xingxin.hx@...nanolis.org>, <baolin.wang@...ux.alibaba.com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, <peternewman@...gle.com>
Subject: Re: [PATCH v3 18/19] x86/resctrl: Add cpu offline callback for
 resctrl work

Hi James,

On 3/20/2023 10:26 AM, James Morse wrote:

> -static int resctrl_offline_cpu(unsigned int cpu)
> -{
> -	struct rdtgroup *rdtgrp;
>  	struct rdt_resource *r;
>  
>  	mutex_lock(&rdtgroup_mutex);
> +	resctrl_offline_cpu(cpu);
> +
>  	for_each_capable_rdt_resource(r)
>  		domain_remove_cpu(cpu, r);
> -	list_for_each_entry(rdtgrp, &rdt_all_groups, rdtgroup_list) {
> -		if (cpumask_test_and_clear_cpu(cpu, &rdtgrp->cpu_mask)) {
> -			clear_childcpus(rdtgrp, cpu);
> -			break;
> -		}
> -	}
>  	clear_closid_rmid(cpu);
>  	mutex_unlock(&rdtgroup_mutex);
>  

I find this and the previous patch to be very complicated. It is not clear
to me why resctrl_offline_cpu(cpu) is required to be before offline of domain.
Previous patch would not be needed if the existing order of operations
is maintained.

Reinette