hrtimer.h

Go to the documentation of this file.

/*
 *  include/linux/hrtimer.h
 *
 *  hrtimers - High-resolution kernel timers
 *
 *   Copyright(C) 2005, Thomas Gleixner <[email protected]>
 *   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
 */
#ifndef _LINUX_HRTIMER_H
#define _LINUX_HRTIMER_H

#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 */
    HRTIMER_MODE_ABS_PINNED = 0x02,
    HRTIMER_MODE_REL_PINNED = 0x03,
};

/*
 * 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.
 */
#define HRTIMER_STATE_INACTIVE  0x00
#define HRTIMER_STATE_ENQUEUED  0x01
#define HRTIMER_STATE_CALLBACK  0x02
#define HRTIMER_STATE_MIGRATE   0x04

struct hrtimer {
    struct timerqueue_node      node;
    ktime_t             _softexpires;
    enum hrtimer_restart        (*function)(struct hrtimer *);
    struct hrtimer_clock_base   *base;
    unsigned long           state;
#ifdef CONFIG_TIMER_STATS
    int             start_pid;
    void                *start_site;
    char                start_comm[16];
#endif
};

struct hrtimer_sleeper {
    struct hrtimer timer;
    struct task_struct *task;
};

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 {
    HRTIMER_BASE_MONOTONIC,
    HRTIMER_BASE_REALTIME,
    HRTIMER_BASE_BOOTTIME,
    HRTIMER_MAX_CLOCK_BASES,
};

/*
 * 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()
 * @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;
#ifdef CONFIG_HIGH_RES_TIMERS
    ktime_t             expires_next;
    int             hres_active;
    int             hang_detected;
    unsigned long           nr_events;
    unsigned long           nr_retries;
    unsigned long           nr_hangs;
    ktime_t             max_hang_time;
#endif
    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());
}

#ifdef CONFIG_HIGH_RES_TIMERS
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 }
# define MONOTONIC_RES_NSEC HIGH_RES_NSEC
# define KTIME_MONOTONIC_RES    KTIME_HIGH_RES

extern void clock_was_set_delayed(void);

#else

# define MONOTONIC_RES_NSEC LOW_RES_NSEC
# define KTIME_MONOTONIC_RES    KTIME_LOW_RES

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) { }

#endif

extern void clock_was_set(void);
#ifdef CONFIG_TIMERFD
extern void timerfd_clock_was_set(void);
#else
static inline void timerfd_clock_was_set(void) { }
#endif
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_update_offsets(ktime_t *offs_real, ktime_t *offs_boot);

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);

#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
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);
#else
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) { }
#endif

/* 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))
#endif

/* Show pending timers: */
extern void sysrq_timer_list_show(void);

#endif