linux/include/linux/rcutiny.h

/* SPDX-License-Identifier: GPL-2.0+ */
/*
 * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
 *
 * Copyright IBM Corporation, 2008
 *
 * Author: Paul E. McKenney <paulmck@linux.ibm.com>
 *
 * For detailed explanation of Read-Copy Update mechanism see -
 *		Documentation/RCU
 */
#ifndef __LINUX_TINY_H
#define __LINUX_TINY_H

#include <asm/param.h> /* for HZ */

struct rcu_gp_oldstate {
	unsigned long rgos_norm;
};

// Maximum number of rcu_gp_oldstate values corresponding to
// not-yet-completed RCU grace periods.
#define NUM_ACTIVE_RCU_POLL_FULL_OLDSTATE 2

/*
 * Are the two oldstate values the same?  See the Tree RCU version for
 * docbook header.
 */
static inline bool same_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp1,
						   struct rcu_gp_oldstate *rgosp2)
{
	return rgosp1->rgos_norm == rgosp2->rgos_norm;
}

unsigned long get_state_synchronize_rcu(void);

static inline void get_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
{
	rgosp->rgos_norm = get_state_synchronize_rcu();
}

unsigned long start_poll_synchronize_rcu(void);

static inline void start_poll_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
{
	rgosp->rgos_norm = start_poll_synchronize_rcu();
}

bool poll_state_synchronize_rcu(unsigned long oldstate);

static inline bool poll_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
{
	return poll_state_synchronize_rcu(rgosp->rgos_norm);
}

static inline void cond_synchronize_rcu(unsigned long oldstate)
{
	might_sleep();
}

static inline void cond_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
{
	cond_synchronize_rcu(rgosp->rgos_norm);
}

static inline unsigned long start_poll_synchronize_rcu_expedited(void)
{
	return start_poll_synchronize_rcu();
}

static inline void start_poll_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp)
{
	rgosp->rgos_norm = start_poll_synchronize_rcu_expedited();
}

static inline void cond_synchronize_rcu_expedited(unsigned long oldstate)
{
	cond_synchronize_rcu(oldstate);
}

static inline void cond_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp)
{
	cond_synchronize_rcu_expedited(rgosp->rgos_norm);
}

extern void rcu_barrier(void);

static inline void synchronize_rcu_expedited(void)
{
	synchronize_rcu();
}

/*
 * Add one more declaration of kvfree() here. It is
 * not so straight forward to just include <linux/mm.h>
 * where it is defined due to getting many compile
 * errors caused by that include.
 */
extern void kvfree(const void *addr);

static inline void __kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
{
	if (head) {
		call_rcu(head, func);
		return;
	}

	// kvfree_rcu(one_arg) call.
	might_sleep();
	synchronize_rcu();
	kvfree((void *) func);
}

#ifdef CONFIG_KASAN_GENERIC
void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func);
#else
static inline void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
{
	__kvfree_call_rcu(head, func);
}
#endif

void rcu_qs(void);

static inline void rcu_softirq_qs(void)
{
	rcu_qs();
}

#define rcu_note_context_switch(preempt) \
	do { \
		rcu_qs(); \
		rcu_tasks_qs(current, (preempt)); \
	} while (0)

static inline int rcu_needs_cpu(void)
{
	return 0;
}

/*
 * Take advantage of the fact that there is only one CPU, which
 * allows us to ignore virtualization-based context switches.
 */
static inline void rcu_virt_note_context_switch(int cpu) { }
static inline void rcu_cpu_stall_reset(void) { }
static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; }
static inline void rcu_irq_exit_check_preempt(void) { }
#define rcu_is_idle_cpu(cpu) \
	(is_idle_task(current) && !in_nmi() && !in_hardirq() && !in_serving_softirq())
static inline void exit_rcu(void) { }
static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
{
	return false;
}
static inline void rcu_preempt_deferred_qs(struct task_struct *t) { }
void rcu_scheduler_starting(void);
static inline void rcu_end_inkernel_boot(void) { }
static inline bool rcu_inkernel_boot_has_ended(void) { return true; }
static inline bool rcu_is_watching(void) { return true; }
static inline void rcu_momentary_dyntick_idle(void) { }
static inline void kfree_rcu_scheduler_running(void) { }
static inline bool rcu_gp_might_be_stalled(void) { return false; }

/* Avoid RCU read-side critical sections leaking across. */
static inline void rcu_all_qs(void) { barrier(); }

/* RCUtree hotplug events */
#define rcutree_prepare_cpu      NULL
#define rcutree_online_cpu       NULL
#define rcutree_offline_cpu      NULL
#define rcutree_dead_cpu         NULL
#define rcutree_dying_cpu        NULL
static inline void rcu_cpu_starting(unsigned int cpu) { }

#endif /* __LINUX_RCUTINY_H */