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

[Frederic Weisbecker]

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!