root/include/linux/sched/isolation.h
#ifndef _LINUX_SCHED_ISOLATION_H
#define _LINUX_SCHED_ISOLATION_H

#include <linux/cpumask.h>
#include <linux/init.h>
#include <linux/tick.h>

enum hk_type {
        /* Inverse of boot-time isolcpus= argument */
        HK_TYPE_DOMAIN_BOOT,
        /*
         * Same as HK_TYPE_DOMAIN_BOOT but also includes the
         * inverse of cpuset isolated partitions. As such it
         * is always a subset of HK_TYPE_DOMAIN_BOOT.
         */
        HK_TYPE_DOMAIN,
        /* Inverse of boot-time isolcpus=managed_irq argument */
        HK_TYPE_MANAGED_IRQ,
        /* Inverse of boot-time nohz_full= or isolcpus=nohz arguments */
        HK_TYPE_KERNEL_NOISE,
        HK_TYPE_MAX,

        /*
         * The following housekeeping types are only set by the nohz_full
         * boot commandline option. So they can share the same value.
         */
        HK_TYPE_TICK    = HK_TYPE_KERNEL_NOISE,
        HK_TYPE_TIMER   = HK_TYPE_KERNEL_NOISE,
        HK_TYPE_RCU     = HK_TYPE_KERNEL_NOISE,
        HK_TYPE_MISC    = HK_TYPE_KERNEL_NOISE,
        HK_TYPE_WQ      = HK_TYPE_KERNEL_NOISE,
        HK_TYPE_KTHREAD = HK_TYPE_KERNEL_NOISE
};

#ifdef CONFIG_CPU_ISOLATION
DECLARE_STATIC_KEY_FALSE(housekeeping_overridden);
extern int housekeeping_any_cpu(enum hk_type type);
extern const struct cpumask *housekeeping_cpumask(enum hk_type type);
extern bool housekeeping_enabled(enum hk_type type);
extern void housekeeping_affine(struct task_struct *t, enum hk_type type);
extern bool housekeeping_test_cpu(int cpu, enum hk_type type);
extern int housekeeping_update(struct cpumask *isol_mask);
extern void __init housekeeping_init(void);

#else

static inline int housekeeping_any_cpu(enum hk_type type)
{
        return smp_processor_id();
}

static inline const struct cpumask *housekeeping_cpumask(enum hk_type type)
{
        return cpu_possible_mask;
}

static inline bool housekeeping_enabled(enum hk_type type)
{
        return false;
}

static inline void housekeeping_affine(struct task_struct *t,
                                       enum hk_type type) { }

static inline bool housekeeping_test_cpu(int cpu, enum hk_type type)
{
        return true;
}

static inline int housekeeping_update(struct cpumask *isol_mask) { return 0; }
static inline void housekeeping_init(void) { }
#endif /* CONFIG_CPU_ISOLATION */

static inline bool housekeeping_cpu(int cpu, enum hk_type type)
{
#ifdef CONFIG_CPU_ISOLATION
        if (static_branch_unlikely(&housekeeping_overridden))
                return housekeeping_test_cpu(cpu, type);
#endif
        return true;
}

static inline bool cpu_is_isolated(int cpu)
{
        return !housekeeping_test_cpu(cpu, HK_TYPE_DOMAIN);
}

#endif /* _LINUX_SCHED_ISOLATION_H */