linux-kernel - Re: [PATCH v7 08/31] x86/resctrl: Clean up domain_remove_cpu

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Message-ID: <3053177d-0eec-4392-9164-a1b93acf8494@intel.com>
Date: Fri, 25 Jul 2025 16:22:44 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghuay@...dia.com>, "Maciej
 Wieczor-Retman" <maciej.wieczor-retman@...el.com>, Peter Newman
	<peternewman@...gle.com>, James Morse <james.morse@....com>, Babu Moger
	<babu.moger@....com>, Drew Fustini <dfustini@...libre.com>, Dave Martin
	<Dave.Martin@....com>, Anil Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	Chen Yu <yu.c.chen@...el.com>
CC: <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<patches@...ts.linux.dev>
Subject: Re: [PATCH v7 08/31] x86/resctrl: Clean up domain_remove_cpu_ctrl()

Hi Tony,

On 7/11/25 4:53 PM, Tony Luck wrote:
> For symmetry with domain_remove_cpu_mon() refactor to take an
> early return when removing a CPU does not empty the domain.
> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---
>  arch/x86/kernel/cpu/resctrl/core.c | 29 ++++++++++++++---------------
>  1 file changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 49e17c246c60..0c5ada54bb20 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -602,25 +602,24 @@ static void domain_remove_cpu_ctrl(int cpu, struct rdt_resource *r)
>  	if (!domain_header_is_valid(hdr, RESCTRL_CTRL_DOMAIN, r->rid))
>  		return;
>  
> +	cpumask_clear_cpu(cpu, &hdr->cpu_mask);
> +	if (!cpumask_empty(&hdr->cpu_mask))
> +		return;
> +
>  	d = container_of(hdr, struct rdt_ctrl_domain, hdr);
>  	hw_dom = resctrl_to_arch_ctrl_dom(d);
>  
> -	cpumask_clear_cpu(cpu, &d->hdr.cpu_mask);
> -	if (cpumask_empty(&d->hdr.cpu_mask)) {
> -		resctrl_offline_ctrl_domain(r, d);
> -		list_del_rcu(&d->hdr.list);
> -		synchronize_rcu();
> -
> -		/*
> -		 * rdt_ctrl_domain "d" is going to be freed below, so clear
> -		 * its pointer from pseudo_lock_region struct.
> -		 */
> -		if (d->plr)
> -			d->plr->d = NULL;
> -		ctrl_domain_free(hw_dom);
> +	resctrl_offline_ctrl_domain(r, d);
> +	list_del_rcu(&d->hdr.list);

nit: this can just reference hdr directly.

Reinette