kernel/sched/isolation.c

/*
 *  Housekeeping management. Manage the targets for routine code that can run on
 *  any CPU: unbound workqueues, timers, kthreads and any offloadable work.
 *
 * Copyright (C) 2017 Red Hat, Inc., Frederic Weisbecker
 *
 */

#include <linux/sched/isolation.h>
#include <linux/tick.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/static_key.h>

DEFINE_STATIC_KEY_FALSE(housekeeping_overriden);
EXPORT_SYMBOL_GPL(housekeeping_overriden);
static cpumask_var_t housekeeping_mask;
static unsigned int housekeeping_flags;

int housekeeping_any_cpu(enum hk_flags flags)
{
	if (static_branch_unlikely(&housekeeping_overriden))
		if (housekeeping_flags & flags)
			return cpumask_any_and(housekeeping_mask, cpu_online_mask);
	return smp_processor_id();
}
EXPORT_SYMBOL_GPL(housekeeping_any_cpu);

const struct cpumask *housekeeping_cpumask(enum hk_flags flags)
{
	if (static_branch_unlikely(&housekeeping_overriden))
		if (housekeeping_flags & flags)
			return housekeeping_mask;
	return cpu_possible_mask;
}
EXPORT_SYMBOL_GPL(housekeeping_cpumask);

void housekeeping_affine(struct task_struct *t, enum hk_flags flags)
{
	if (static_branch_unlikely(&housekeeping_overriden))
		if (housekeeping_flags & flags)
			set_cpus_allowed_ptr(t, housekeeping_mask);
}
EXPORT_SYMBOL_GPL(housekeeping_affine);

bool housekeeping_test_cpu(int cpu, enum hk_flags flags)
{
	if (static_branch_unlikely(&housekeeping_overriden))
		if (housekeeping_flags & flags)
			return cpumask_test_cpu(cpu, housekeeping_mask);
	return true;
}
EXPORT_SYMBOL_GPL(housekeeping_test_cpu);

void __init housekeeping_init(void)
{
	if (!housekeeping_flags)
		return;

	static_branch_enable(&housekeeping_overriden);

	/* We need at least one CPU to handle housekeeping work */
	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
}

#ifdef CONFIG_NO_HZ_FULL
static int __init housekeeping_nohz_full_setup(char *str)
{
	cpumask_var_t non_housekeeping_mask;

	alloc_bootmem_cpumask_var(&non_housekeeping_mask);
	if (cpulist_parse(str, non_housekeeping_mask) < 0) {
		pr_warn("Housekeeping: Incorrect nohz_full cpumask\n");
		free_bootmem_cpumask_var(non_housekeeping_mask);
		return 0;
	}

	alloc_bootmem_cpumask_var(&housekeeping_mask);
	cpumask_andnot(housekeeping_mask, cpu_possible_mask, non_housekeeping_mask);

	if (cpumask_empty(housekeeping_mask))
		cpumask_set_cpu(smp_processor_id(), housekeeping_mask);

	housekeeping_flags = HK_FLAG_TICK | HK_FLAG_TIMER |
				HK_FLAG_RCU | HK_FLAG_MISC;

	tick_nohz_full_setup(non_housekeeping_mask);

	free_bootmem_cpumask_var(non_housekeeping_mask);

	return 1;
}
__setup("nohz_full=", housekeeping_nohz_full_setup);
#endif