linux-kernel - Re: [PATCH v8 08/32] x86/resctrl: Clean up domain_remove_cpu

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Message-ID: <0825f3c0-58f2-4421-912b-cb4964e4f6c9@intel.com>
Date: Wed, 13 Aug 2025 20:59:51 -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 v8 08/32] x86/resctrl: Clean up domain_remove_cpu_ctrl()

Hi Tony,

On 8/11/25 11:16 AM, 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.

"refactor" -> "refactor domain_remove_cpu_ctrl()"
so that changelog stands on its own and is not continuation of subject.

> 
> 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 448c2bf9837d..911100994fcd 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -603,25 +603,24 @@ 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;
> +

Here is another instance where the domain_header_is_valid() checking is
moved away from the subsequent container_of() that it is intended to protect.

>  	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);

Missing the change mentioned in cover letter.

> +	synchronize_rcu();
>  
> -		return;
> -	}
> +	/*
> +	 * 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);
>  }
>  
>  static void domain_remove_cpu_mon(int cpu, struct rdt_resource *r)

Reinette