linux-kernel - Re: [PATCH v14 7/7] timers: Exclude isolated cpus from timer migration

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aRSv-kcSj5kc6CJ9@localhost.localdomain>
Date: Wed, 12 Nov 2025 17:04:10 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Gabriele Monaco <gmonaco@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Waiman Long <llong@...hat.com>,
	"John B . Wyatt IV" <jwyatt@...hat.com>,
	"John B . Wyatt IV" <sageofredondo@...il.com>
Subject: Re: [PATCH v14 7/7] timers: Exclude isolated cpus from timer
 migration

Le Tue, Nov 04, 2025 at 11:47:39AM +0100, Gabriele Monaco a écrit :
> +static int __init tmigr_init_isolation(void)
> +{
> +	struct work_struct __percpu *works __free(free_percpu) =
> +		alloc_percpu(struct work_struct);
> +	cpumask_var_t cpumask __free(free_cpumask_var) = CPUMASK_VAR_NULL;
> +	int cpu;
> +
> +	static_branch_enable(&tmigr_exclude_isolated);
> +	if (!housekeeping_enabled(HK_TYPE_DOMAIN))
> +		return 0;
> +	if (!alloc_cpumask_var(&cpumask, GFP_KERNEL))
> +		return -ENOMEM;
> +	if (!works)
> +		return -ENOMEM;
> +	cpumask_andnot(cpumask, tmigr_available_cpumask,
> +		       housekeeping_cpumask(HK_TYPE_DOMAIN));
> +	cpumask_and(cpumask, cpumask, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE));
> +	/* Never disable the tick CPU, see tmigr_is_isolated for details */
> +	for_each_cpu(cpu, cpumask) {
> +		if (!tick_nohz_cpu_hotpluggable(cpu)) {
> +			cpumask_clear_cpu(cpu, cpumask);
> +			break;
> +		}
> +	}
> +	for_each_cpu(cpu, cpumask) {
> +		struct work_struct *work = per_cpu_ptr(works, cpu);
> +
> +		INIT_WORK(work, tmigr_cpu_isolate);
> +		schedule_work_on(cpu, work);
> +	}
> +	for_each_cpu(cpu, cpumask)
> +		flush_work(per_cpu_ptr(works, cpu));
> +
>  	return 0;

This duplicates a lot tmigr_isolated_exclude_cpumask().
Would this work?

static int __init tmigr_init_isolation(void)
{
	cpumask_var_t cpumask __free(free_cpumask_var) = CPUMASK_VAR_NULL;

	static_branch_enable(&tmigr_exclude_isolated);

	if (!housekeeping_enabled(HK_TYPE_DOMAIN))
		return 0;
	if (!alloc_cpumask_var(&cpumask, GFP_KERNEL))
		return -ENOMEM;

	cpumask_andnot(cpumask, cpu_possible_mask, housekeeping_cpumask(HK_TYPE_DOMAIN));

	return tmigr_isolated_exclude_cpumask(cpumask);
}

If so please add my Reviewed-by to the next version.

Thanks!