hrtimers: add missing docbook comments to struct hrtimer

[linux-2.6/mini2440.git] / include / linux / hrtimer.h

/*
 *  include/linux/hrtimer.h
 *
 *  hrtimers - High-resolution kernel timers
 *
 *   Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
 *   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>


struct hrtimer_clock_base;
struct hrtimer_cpu_base;

/*
 * Mode arguments of xxx_hrtimer functions:
 */
enum hrtimer_mode {
        HRTIMER_MODE_ABS,       /* Time value is absolute */
        HRTIMER_MODE_REL,       /* Time value is relative to now */
};

/*
 * Return values for the callback function
 */
enum hrtimer_restart {
        HRTIMER_NORESTART,      /* Timer is not restarted */
        HRTIMER_RESTART,        /* Timer must be restarted */
};

/*
 * hrtimer callback modes:
 *
 *      HRTIMER_CB_SOFTIRQ:             Callback must run in softirq context
 *      HRTIMER_CB_IRQSAFE:             Callback may run in hardirq context
 *      HRTIMER_CB_IRQSAFE_NO_RESTART:  Callback may run in hardirq context and
 *                                      does not restart the timer
 *      HRTIMER_CB_IRQSAFE_PERCPU:      Callback must run in hardirq context
 *                                      Special mode for tick emulation and
 *                                      scheduler timer. Such timers are per
 *                                      cpu and not allowed to be migrated on
 *                                      cpu unplug.
 *      HRTIMER_CB_IRQSAFE_UNLOCKED:    Callback should run in hardirq context
 *                                      with timer->base lock unlocked
 *                                      used for timers which call wakeup to
 *                                      avoid lock order problems with rq->lock
 */
enum hrtimer_cb_mode {
        HRTIMER_CB_SOFTIRQ,
        HRTIMER_CB_IRQSAFE,
        HRTIMER_CB_IRQSAFE_NO_RESTART,
        HRTIMER_CB_IRQSAFE_PERCPU,
        HRTIMER_CB_IRQSAFE_UNLOCKED,
};

/*
 * Values to track state of the timer
 *
 * Possible states:
 *
 * 0x00         inactive
 * 0x01         enqueued into rbtree
 * 0x02         callback function running
 * 0x04         callback pending (high resolution mode)
 *
 * Special cases:
 * 0x03         callback function running and enqueued
 *              (was requeued on another CPU)
 * 0x09         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 bit in the above scenario.
 *
 * 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_PENDING   0x04
#define HRTIMER_STATE_MIGRATE   0x08

/**
 * 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. 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)
 * @cb_mode:    high resolution timer feature to select the callback execution
 *               mode
 * @cb_entry:   list head to enqueue an expired timer into the callback list
 * @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 rb_node                  node;
        ktime_t                         _expires;
        ktime_t                         _softexpires;
        enum hrtimer_restart            (*function)(struct hrtimer *);
        struct hrtimer_clock_base       *base;
        unsigned long                   state;
        enum hrtimer_cb_mode            cb_mode;
        struct list_head                cb_entry;
#ifdef CONFIG_TIMER_STATS
        void                            *start_site;
        char                            start_comm[16];
        int                             start_pid;
#endif
};

/**
 * 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.
 * @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
 * @softirq_time:       the time when running the hrtimer queue in the softirq
 * @offset:             offset of this clock to the monotonic base
 * @reprogram:          function to reprogram the timer event
 */
struct hrtimer_clock_base {
        struct hrtimer_cpu_base *cpu_base;
        clockid_t               index;
        struct rb_root          active;
        struct rb_node          *first;
        ktime_t                 resolution;
        ktime_t                 (*get_time)(void);
        ktime_t                 (*get_softirq_time)(void);
        ktime_t                 softirq_time;
#ifdef CONFIG_HIGH_RES_TIMERS
        ktime_t                 offset;
        int                     (*reprogram)(struct hrtimer *t,
                                             struct hrtimer_clock_base *b,
                                             ktime_t n);
#endif
};

#define HRTIMER_MAX_CLOCK_BASES 2

/*
 * struct hrtimer_cpu_base - the per cpu clock bases
 * @lock:               lock protecting the base and associated clock bases
 *                      and timers
 * @clock_base:         array of clock bases for this cpu
 * @curr_timer:         the timer which is executing a callback right now
 * @expires_next:       absolute time of the next event which was scheduled
 *                      via clock_set_next_event()
 * @hres_active:        State of high resolution mode
 * @check_clocks:       Indictator, when set evaluate time source and clock
 *                      event devices whether high resolution mode can be
 *                      activated.
 * @cb_pending:         Expired timers are moved from the rbtree to this
 *                      list in the timer interrupt. The list is processed
 *                      in the softirq.
 * @nr_events:          Total number of timer interrupt events
 */
struct hrtimer_cpu_base {
        spinlock_t                      lock;
        struct hrtimer_clock_base       clock_base[HRTIMER_MAX_CLOCK_BASES];
        struct list_head                cb_pending;
#ifdef CONFIG_HIGH_RES_TIMERS
        ktime_t                         expires_next;
        int                             hres_active;
        unsigned long                   nr_events;
#endif
};

static inline void hrtimer_set_expires(struct hrtimer *timer, ktime_t time)
{
        timer->_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->_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->_expires = ktime_add_safe(time, ns_to_ktime(delta));
}

static inline void hrtimer_set_expires_tv64(struct hrtimer *timer, s64 tv64)
{
        timer->_expires.tv64 = tv64;
        timer->_softexpires.tv64 = tv64;
}

static inline void hrtimer_add_expires(struct hrtimer *timer, ktime_t time)
{
        timer->_expires = ktime_add_safe(timer->_expires, time);
        timer->_softexpires = ktime_add_safe(timer->_softexpires, time);
}

static inline void hrtimer_add_expires_ns(struct hrtimer *timer, unsigned long ns)
{
        timer->_expires = ktime_add_ns(timer->_expires, ns);
        timer->_softexpires = ktime_add_ns(timer->_softexpires, ns);
}

static inline ktime_t hrtimer_get_expires(const struct hrtimer *timer)
{
        return timer->_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->_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->_expires);
}

static inline ktime_t hrtimer_expires_remaining(const struct hrtimer *timer)
{
    return ktime_sub(timer->_expires, timer->base->get_time());
}

#ifdef CONFIG_HIGH_RES_TIMERS
struct clock_event_device;

extern void clock_was_set(void);
extern void hres_timers_resume(void);
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

#else

# define MONOTONIC_RES_NSEC     LOW_RES_NSEC
# define KTIME_MONOTONIC_RES    KTIME_LOW_RES

/*
 * 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.
 */
static inline void clock_was_set(void) { }
static inline void hrtimer_peek_ahead_timers(void) { }

static inline void hres_timers_resume(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;
}
#endif

extern ktime_t ktime_get(void);
extern ktime_t ktime_get_real(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);

#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_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.
 */
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 | HRTIMER_STATE_PENDING);
}

/*
 * 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(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);

/*
 * Timer-statistics info:
 */
#ifdef CONFIG_TIMER_STATS

extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
                                     void *timerf, char *comm,
                                     unsigned int timer_flag);

static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
{
        timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
                                 timer->function, timer->start_comm, 0);
}

extern void __timer_stats_hrtimer_set_start_info(struct hrtimer *timer,
                                                 void *addr);

static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
{
        __timer_stats_hrtimer_set_start_info(timer, __builtin_return_address(0));
}

static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
{
        timer->start_site = NULL;
}
#else
static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
{
}

static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
{
}

static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
{
}
#endif

#endif