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 *  include/linux/hrtimer.h
 *  hrtimers - High-resolution kernel timers
 *   Copyright(C) 2005, Thomas Gleixner <>
 *   Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
 *  data type definitions, declarations, prototypes
 *  Started by: Thomas Gleixner and Ingo Molnar
 *  For licencing details see kernel-base/COPYING

#include <linux/rbtree.h>
#include <linux/ktime.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/wait.h>

 * Mode arguments of xxx_hrtimer functions:
enum hrtimer_mode {
	HRTIMER_ABS,	/* Time value is absolute */
	HRTIMER_REL,	/* Time value is relative to now */

enum hrtimer_restart {

#define HRTIMER_INACTIVE	((void *)1UL)

struct hrtimer_base;

 * struct hrtimer - the basic hrtimer structure
 * @node:	red black tree node for time ordered insertion
 * @expires:	the absolute expiry time in the hrtimers internal
 *		representation. The time is related to the clock on
 *		which the timer is based.
 * @function:	timer expiry callback function
 * @base:	pointer to the timer base (per cpu and per clock)
 * The hrtimer structure must be initialized by init_hrtimer_#CLOCKTYPE()
struct hrtimer {
	struct rb_node		node;
	ktime_t			expires;
	int			(*function)(struct hrtimer *);
	struct hrtimer_base	*base;

 * struct hrtimer_sleeper - simple sleeper structure
 * @timer:	embedded timer structure
 * @task:	task to wake up
 * task is set to NULL, when the timer expires.
struct hrtimer_sleeper {
	struct hrtimer timer;
	struct task_struct *task;

 * struct hrtimer_base - the timer base for a specific clock
 * @index:		clock type index for per_cpu support when moving a timer
 *			to a base on another cpu.
 * @lock:		lock protecting the base and associated timers
 * @active:		red black tree root node for the active timers
 * @first:		pointer to the timer node which expires first
 * @resolution:		the resolution of the clock, in nanoseconds
 * @get_time:		function to retrieve the current time of the clock
 * @get_softirq_time:	function to retrieve the current time from the softirq
 * @curr_timer:		the timer which is executing a callback right now
 * @softirq_time:	the time when running the hrtimer queue in the softirq
 * @lock_key:		the lock_class_key for use with lockdep
struct hrtimer_base {
	clockid_t		index;
	spinlock_t		lock;
	struct rb_root		active;
	struct rb_node		*first;
	ktime_t			resolution;
	ktime_t			(*get_time)(void);
	ktime_t			(*get_softirq_time)(void);
	struct hrtimer		*curr_timer;
	ktime_t			softirq_time;
	struct lock_class_key lock_key;

 * clock_was_set() is a NOP for non- high-resolution systems. The
 * time-sorted order guarantees that a timer does not expire early and
 * is expired in the next softirq when the clock was advanced.
#define clock_was_set()		do { } while (0)

/* Exported timer functions: */

/* Initialize timers: */
extern void hrtimer_init(struct hrtimer *timer, clockid_t which_clock,
			 enum hrtimer_mode mode);

/* Basic timer operations: */
extern int hrtimer_start(struct hrtimer *timer, ktime_t tim,
			 const enum hrtimer_mode mode);
extern int hrtimer_cancel(struct hrtimer *timer);
extern int hrtimer_try_to_cancel(struct hrtimer *timer);

#define hrtimer_restart(timer) hrtimer_start((timer), (timer)->expires, HRTIMER_ABS)

/* Query timers: */
extern ktime_t hrtimer_get_remaining(const struct hrtimer *timer);
extern int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp);

extern ktime_t hrtimer_get_next_event(void);

static inline int hrtimer_active(const struct hrtimer *timer)
	return rb_parent(&timer->node) != &timer->node;

/* Forward a hrtimer so it expires after now: */
extern unsigned long
hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);

/* Precise sleep: */
extern long hrtimer_nanosleep(struct timespec *rqtp,
			      struct timespec __user *rmtp,
			      const enum hrtimer_mode mode,
			      const clockid_t clockid);
extern long hrtimer_nanosleep_restart(struct restart_block *restart_block);

extern void hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
				 struct task_struct *tsk);

/* Soft interrupt function to run the hrtimer queues: */
extern void hrtimer_run_queues(void);

/* Bootup initialization: */
extern void __init hrtimers_init(void);