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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/percpu.h>
#include <linux/timer.h>
#include <linux/timerqueue.h>
struct hrtimer_clock_base;
struct hrtimer_cpu_base;
* Mode arguments of xxx_hrtimer functions:
* HRTIMER_MODE_ABS - Time value is absolute
* HRTIMER_MODE_REL - Time value is relative to now
* HRTIMER_MODE_PINNED - Timer is bound to CPU (is only considered
* when starting the timer)
* HRTIMER_MODE_SOFT - Timer callback function will be executed in
* soft irq context
enum hrtimer_mode {
* 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
* The callback state is not part of the timer->state because clearing it would
* mean touching the timer after the callback, this makes it impossible to free
* the timer from the callback function.
* Therefore we track the callback state in:
* timer->base->cpu_base->running == timer
* On SMP it is possible to have a "callback function running and enqueued"
* status. 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.
* 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)
* @is_rel: Set if the timer was armed relative
* @is_soft: Set if hrtimer will be expired in soft interrupt context.
* 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;
u8 state;
u8 is_rel;
u8 is_soft;
* 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;
#ifdef CONFIG_64BIT
# define __hrtimer_clock_base_align ____cacheline_aligned
# define __hrtimer_clock_base_align
* 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
* @seq: seqcount around __run_hrtimer
* @running: pointer to the currently running hrtimer
* @active: red black tree root node for the active timers
* @get_time: function to retrieve the current time of the clock
* @offset: offset of this clock to the monotonic base
struct hrtimer_clock_base {
struct hrtimer_cpu_base *cpu_base;
unsigned int index;
clockid_t clockid;
seqcount_t seq;
struct hrtimer *running;
struct timerqueue_head active;
ktime_t (*get_time)(void);
ktime_t offset;
} __hrtimer_clock_base_align;
enum hrtimer_base_type {
* struct hrtimer_cpu_base - the per cpu clock bases
* @lock: lock protecting the base and associated clock bases
* and timers
* @cpu: cpu number
* @active_bases: Bitfield to mark bases with active timers
* @clock_was_set_seq: Sequence counter of clock was set events
* @hres_active: State of high resolution mode
* @in_hrtirq: hrtimer_interrupt() is currently executing
* @hang_detected: The last hrtimer interrupt detected a hang
* @softirq_activated: displays, if the softirq is raised - update of softirq
* related settings is not required then.
* @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
* @expires_next: absolute time of the next event, is required for remote
* hrtimer enqueue; it is the total first expiry time (hard
* and soft hrtimer are taken into account)
* @next_timer: Pointer to the first expiring timer
* @softirq_expires_next: Time to check, if soft queues needs also to be expired
* @softirq_next_timer: Pointer to the first expiring softirq based timer
* @clock_base: array of clock bases for this cpu
* Note: next_timer is just an optimization for __remove_hrtimer().
* Do not dereference the pointer because it is not reliable on
* cross cpu removals.
struct hrtimer_cpu_base {
raw_spinlock_t lock;
unsigned int cpu;
unsigned int active_bases;
unsigned int clock_was_set_seq;
unsigned int hres_active : 1,
in_hrtirq : 1,
hang_detected : 1,
softirq_activated : 1;
unsigned int nr_events;
unsigned short nr_retries;
unsigned short nr_hangs;
unsigned int max_hang_time;
ktime_t expires_next;
struct hrtimer *next_timer;
ktime_t softirq_expires_next;
struct hrtimer *softirq_next_timer;
struct hrtimer_clock_base clock_base[HRTIMER_MAX_CLOCK_BASES];
} ____cacheline_aligned;
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, u64 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;
timer->_softexpires = 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;
static inline s64 hrtimer_get_softexpires_tv64(const struct hrtimer *timer)
return timer->_softexpires;
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());
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)
timer->base->cpu_base->hres_active : 0;
struct clock_event_device;
extern void hrtimer_interrupt(struct clock_event_device *dev);
* 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
extern void clock_was_set_delayed(void);
extern unsigned int hrtimer_resolution;
#define hrtimer_resolution (unsigned int)LOW_RES_NSEC
static inline void clock_was_set_delayed(void) { }
static inline ktime_t
__hrtimer_expires_remaining_adjusted(const struct hrtimer *timer, ktime_t now)
ktime_t rem = ktime_sub(timer->node.expires, now);
* Adjust relative timers for the extra we added in
* hrtimer_start_range_ns() to prevent short timeouts.
if (IS_ENABLED(CONFIG_TIME_LOW_RES) && timer->is_rel)
rem -= hrtimer_resolution;
return rem;
static inline ktime_t
hrtimer_expires_remaining_adjusted(const struct hrtimer *timer)
return __hrtimer_expires_remaining_adjusted(timer,
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);
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 void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
u64 range_ns, const enum hrtimer_mode mode);
* hrtimer_start - (re)start an hrtimer
* @timer: the timer to be added
* @tim: expiry time
* @mode: timer mode: absolute (HRTIMER_MODE_ABS) or
* relative (HRTIMER_MODE_REL), and pinned (HRTIMER_MODE_PINNED);
* softirq based mode is considered for debug purpose only!
static inline void hrtimer_start(struct hrtimer *timer, ktime_t tim,
const enum hrtimer_mode mode)
hrtimer_start_range_ns(timer, tim, 0, mode);
extern int hrtimer_cancel(struct hrtimer *timer);
extern int hrtimer_try_to_cancel(struct hrtimer *timer);
static inline void hrtimer_start_expires(struct hrtimer *timer,
enum hrtimer_mode mode)
u64 delta;
ktime_t soft, hard;
soft = hrtimer_get_softexpires(timer);
hard = hrtimer_get_expires(timer);
delta = ktime_to_ns(ktime_sub(hard, soft));
hrtimer_start_range_ns(timer, soft, delta, mode);
static inline void hrtimer_restart(struct hrtimer *timer)
hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
/* Query timers: */
extern ktime_t __hrtimer_get_remaining(const struct hrtimer *timer, bool adjust);
static inline ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
return __hrtimer_get_remaining(timer, false);
extern u64 hrtimer_get_next_event(void);
extern u64 hrtimer_next_event_without(const struct hrtimer *exclude);
extern bool hrtimer_active(const struct hrtimer *timer);
* 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->base->running == timer;
/* Forward a hrtimer so it expires after now: */
extern u64
hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);
* hrtimer_forward_now - forward the timer expiry so it expires after now
* @timer: hrtimer to forward
* @interval: the interval to forward
* Forward the timer expiry so it will expire after the current time
* of the hrtimer clock base. Returns the number of overruns.
* Can be safely called from the callback function of @timer. If
* called from other contexts @timer must neither be enqueued nor
* running the callback and the caller needs to take care of
* serialization.
* Note: This only updates the timer expiry value and does not requeue
* the timer.
static inline u64 hrtimer_forward_now(struct hrtimer *timer,
ktime_t interval)
return hrtimer_forward(timer, timer->base->get_time(), interval);
/* Precise sleep: */
extern int nanosleep_copyout(struct restart_block *, struct timespec64 *);
extern long hrtimer_nanosleep(const struct timespec64 *rqtp,
const enum hrtimer_mode mode,
const clockid_t clockid);
extern void hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
struct task_struct *tsk);
extern int schedule_hrtimeout_range(ktime_t *expires, u64 delta,
const enum hrtimer_mode mode);
extern int schedule_hrtimeout_range_clock(ktime_t *expires,
u64 delta,
const enum hrtimer_mode mode,
clockid_t clock_id);
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);
/* Bootup initialization: */
extern void __init hrtimers_init(void);
/* Show pending timers: */
extern void sysrq_timer_list_show(void);
int hrtimers_prepare_cpu(unsigned int cpu);
int hrtimers_dead_cpu(unsigned int cpu);
#define hrtimers_dead_cpu NULL