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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>
#include <linux/percpu.h>
#include <linux/timer.h>
#include <linux/timerqueue.h>
struct hrtimer_clock_base;
struct hrtimer_cpu_base;
* Mode arguments of xxx_hrtimer functions:
enum hrtimer_mode {
HRTIMER_MODE_ABS = 0x0, /* Time value is absolute */
HRTIMER_MODE_REL = 0x1, /* Time value is relative to now */
HRTIMER_MODE_PINNED = 0x02, /* Timer is bound to CPU */
* Return values for the callback function
enum hrtimer_restart {
HRTIMER_NORESTART, /* Timer is not restarted */
HRTIMER_RESTART, /* Timer must be restarted */
* Values to track state of the timer
* Possible states:
* 0x00 inactive
* 0x01 enqueued into rbtree
* 0x02 callback function running
* 0x04 timer is migrated to another cpu
* Special cases:
* 0x03 callback function running and enqueued
* (was requeued on another CPU)
* 0x05 timer was migrated on CPU hotunplug
* The "callback function running and enqueued" status is only possible on
* SMP. It happens for example when a posix timer expired and the callback
* queued a signal. Between dropping the lock which protects the posix timer
* and reacquiring the base lock of the hrtimer, another CPU can deliver the
* signal and rearm the timer. We have to preserve the callback running state,
* as otherwise the timer could be removed before the softirq code finishes the
* the handling of the timer.
* The HRTIMER_STATE_ENQUEUED bit is always or'ed to the current state
* to preserve the HRTIMER_STATE_CALLBACK in the above scenario. This
* also affects HRTIMER_STATE_MIGRATE where the preservation is not
* necessary. HRTIMER_STATE_MIGRATE is cleared after the timer is
* enqueued on the new cpu.
* All state transitions are protected by cpu_base->lock.
* struct hrtimer - the basic hrtimer structure
* @node: timerqueue node, which also manages node.expires,
* the absolute expiry time in the hrtimers internal
* representation. The time is related to the clock on
* which the timer is based. Is setup by adding
* slack to the _softexpires value. For non range timers
* identical to _softexpires.
* @_softexpires: the absolute earliest expiry time of the hrtimer.
* The time which was given as expiry time when the timer
* was armed.
* @function: timer expiry callback function
* @base: pointer to the timer base (per cpu and per clock)
* @state: state information (See bit values above)
* @start_site: timer statistics field to store the site where the timer
* was started
* @start_comm: timer statistics field to store the name of the process which
* started the timer
* @start_pid: timer statistics field to store the pid of the task which
* started the timer
* The hrtimer structure must be initialized by hrtimer_init()
struct hrtimer {
struct timerqueue_node node;
ktime_t _softexpires;
enum hrtimer_restart (*function)(struct hrtimer *);
struct hrtimer_clock_base *base;
unsigned long state;
int start_pid;
void *start_site;
char start_comm[16];
* 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_clock_base - the timer base for a specific clock
* @cpu_base: per cpu clock base
* @index: clock type index for per_cpu support when moving a
* timer to a base on another cpu.
* @clockid: clock id for per_cpu support
* @active: red black tree root node for the active timers
* @resolution: the resolution of the clock, in nanoseconds
* @get_time: function to retrieve the current time of the clock
* @softirq_time: the time when running the hrtimer queue in the softirq
* @offset: offset of this clock to the monotonic base
struct hrtimer_clock_base {
struct hrtimer_cpu_base *cpu_base;
int index;
clockid_t clockid;
struct timerqueue_head active;
ktime_t resolution;
ktime_t (*get_time)(void);
ktime_t softirq_time;
ktime_t offset;
enum hrtimer_base_type {
* struct hrtimer_cpu_base - the per cpu clock bases
* @lock: lock protecting the base and associated clock bases
* and timers
* @active_bases: Bitfield to mark bases with active timers
* @clock_was_set: Indicates that clock was set from irq context.
* @expires_next: absolute time of the next event which was scheduled
* via clock_set_next_event()
* @in_hrtirq: hrtimer_interrupt() is currently executing
* @hres_active: State of high resolution mode
* @hang_detected: The last hrtimer interrupt detected a hang
* @nr_events: Total number of hrtimer interrupt events
* @nr_retries: Total number of hrtimer interrupt retries
* @nr_hangs: Total number of hrtimer interrupt hangs
* @max_hang_time: Maximum time spent in hrtimer_interrupt
* @clock_base: array of clock bases for this cpu
struct hrtimer_cpu_base {
raw_spinlock_t lock;
unsigned int active_bases;
unsigned int clock_was_set;
ktime_t expires_next;
int in_hrtirq;
int hres_active;
int hang_detected;
unsigned long nr_events;
unsigned long nr_retries;
unsigned long nr_hangs;
ktime_t max_hang_time;
struct hrtimer_clock_base clock_base[HRTIMER_MAX_CLOCK_BASES];
static inline void hrtimer_set_expires(struct hrtimer *timer, ktime_t time)
timer->node.expires = time;
timer->_softexpires = time;
static inline void hrtimer_set_expires_range(struct hrtimer *timer, ktime_t time, ktime_t delta)
timer->_softexpires = time;
timer->node.expires = ktime_add_safe(time, delta);
static inline void hrtimer_set_expires_range_ns(struct hrtimer *timer, ktime_t time, unsigned long delta)
timer->_softexpires = time;
timer->node.expires = ktime_add_safe(time, ns_to_ktime(delta));
static inline void hrtimer_set_expires_tv64(struct hrtimer *timer, s64 tv64)
timer->node.expires.tv64 = tv64;
timer->_softexpires.tv64 = tv64;
static inline void hrtimer_add_expires(struct hrtimer *timer, ktime_t time)
timer->node.expires = ktime_add_safe(timer->node.expires, time);
timer->_softexpires = ktime_add_safe(timer->_softexpires, time);
static inline void hrtimer_add_expires_ns(struct hrtimer *timer, u64 ns)
timer->node.expires = ktime_add_ns(timer->node.expires, ns);
timer->_softexpires = ktime_add_ns(timer->_softexpires, ns);
static inline ktime_t hrtimer_get_expires(const struct hrtimer *timer)
return timer->node.expires;
static inline ktime_t hrtimer_get_softexpires(const struct hrtimer *timer)
return timer->_softexpires;
static inline s64 hrtimer_get_expires_tv64(const struct hrtimer *timer)
return timer->node.expires.tv64;
static inline s64 hrtimer_get_softexpires_tv64(const struct hrtimer *timer)
return timer->_softexpires.tv64;
static inline s64 hrtimer_get_expires_ns(const struct hrtimer *timer)
return ktime_to_ns(timer->node.expires);
static inline ktime_t hrtimer_expires_remaining(const struct hrtimer *timer)
return ktime_sub(timer->node.expires, timer->base->get_time());
struct clock_event_device;
extern void hrtimer_interrupt(struct clock_event_device *dev);
* In high resolution mode the time reference must be read accurate
static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
return timer->base->get_time();
static inline int hrtimer_is_hres_active(struct hrtimer *timer)
return timer->base->cpu_base->hres_active;
extern void hrtimer_peek_ahead_timers(void);
* The resolution of the clocks. The resolution value is returned in
* the clock_getres() system call to give application programmers an
* idea of the (in)accuracy of timers. Timer values are rounded up to
* this resolution values.
# define HIGH_RES_NSEC 1
# define KTIME_HIGH_RES (ktime_t) { .tv64 = HIGH_RES_NSEC }
extern void clock_was_set_delayed(void);
static inline void hrtimer_peek_ahead_timers(void) { }
* In non high resolution mode the time reference is taken from
* the base softirq time variable.
static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
return timer->base->softirq_time;
static inline int hrtimer_is_hres_active(struct hrtimer *timer)
return 0;
static inline void clock_was_set_delayed(void) { }
extern void clock_was_set(void);
extern void timerfd_clock_was_set(void);
static inline void timerfd_clock_was_set(void) { }
extern void hrtimers_resume(void);
extern ktime_t ktime_get(void);
extern ktime_t ktime_get_real(void);
extern ktime_t ktime_get_boottime(void);
extern ktime_t ktime_get_monotonic_offset(void);
extern ktime_t ktime_get_clocktai(void);
extern ktime_t ktime_get_update_offsets(ktime_t *offs_real, ktime_t *offs_boot,
ktime_t *offs_tai);
DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
/* Exported timer functions: */
/* Initialize timers: */
extern void hrtimer_init(struct hrtimer *timer, clockid_t which_clock,
enum hrtimer_mode mode);
extern void hrtimer_init_on_stack(struct hrtimer *timer, clockid_t which_clock,
enum hrtimer_mode mode);
extern void destroy_hrtimer_on_stack(struct hrtimer *timer);
static inline void hrtimer_init_on_stack(struct hrtimer *timer,
clockid_t which_clock,
enum hrtimer_mode mode)
hrtimer_init(timer, which_clock, mode);
static inline void destroy_hrtimer_on_stack(struct hrtimer *timer) { }
/* Basic timer operations: */
extern int hrtimer_start(struct hrtimer *timer, ktime_t tim,
const enum hrtimer_mode mode);
extern int hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
unsigned long range_ns, const enum hrtimer_mode mode);
extern int
__hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
unsigned long delta_ns,
const enum hrtimer_mode mode, int wakeup);
extern int hrtimer_cancel(struct hrtimer *timer);
extern int hrtimer_try_to_cancel(struct hrtimer *timer);
static inline int hrtimer_start_expires(struct hrtimer *timer,
enum hrtimer_mode mode)
unsigned long delta;
ktime_t soft, hard;
soft = hrtimer_get_softexpires(timer);
hard = hrtimer_get_expires(timer);
delta = ktime_to_ns(ktime_sub(hard, soft));
return hrtimer_start_range_ns(timer, soft, delta, mode);
static inline int hrtimer_restart(struct hrtimer *timer)
return hrtimer_start_expires(timer, HRTIMER_MODE_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);
* A timer is active, when it is enqueued into the rbtree or the
* callback function is running or it's in the state of being migrated
* to another cpu.
static inline int hrtimer_active(const struct hrtimer *timer)
return timer->state != HRTIMER_STATE_INACTIVE;
* Helper function to check, whether the timer is on one of the queues
static inline int hrtimer_is_queued(struct hrtimer *timer)
return timer->state & HRTIMER_STATE_ENQUEUED;
* Helper function to check, whether the timer is running the callback
* function
static inline int hrtimer_callback_running(struct hrtimer *timer)
return timer->state & HRTIMER_STATE_CALLBACK;
/* Forward a hrtimer so it expires after now: */
extern u64
hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);
/* Forward a hrtimer so it expires after the hrtimer's current now */
static inline u64 hrtimer_forward_now(struct hrtimer *timer,
ktime_t interval)
return hrtimer_forward(timer, timer->base->get_time(), 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);
extern int schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
const enum hrtimer_mode mode);
extern int schedule_hrtimeout_range_clock(ktime_t *expires,
unsigned long delta, const enum hrtimer_mode mode, int clock);
extern int schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode);
/* Soft interrupt function to run the hrtimer queues: */
extern void hrtimer_run_queues(void);
extern void hrtimer_run_pending(void);
/* Bootup initialization: */
extern void __init hrtimers_init(void);
#if BITS_PER_LONG < 64
extern u64 ktime_divns(const ktime_t kt, s64 div);
#else /* BITS_PER_LONG < 64 */
# define ktime_divns(kt, div) (u64)((kt).tv64 / (div))
/* Show pending timers: */
extern void sysrq_timer_list_show(void);