alistair23-linux/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>
#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
 *
 * 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.
 */
#define HRTIMER_STATE_INACTIVE	0x00
#define HRTIMER_STATE_ENQUEUED	0x01

/**
 * 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
 * @start_pid:  timer statistics field to store the pid of the task which
 *		started the timer
 * @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
 *
 * 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;
#ifdef CONFIG_TIMER_STATS
	int				start_pid;
	void				*start_site;
	char				start_comm[16];
#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;
};

#ifdef CONFIG_64BIT
# define HRTIMER_CLOCK_BASE_ALIGN	64
#else
# define HRTIMER_CLOCK_BASE_ALIGN	32
#endif

/**
 * 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
 * @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;
	int			index;
	clockid_t		clockid;
	struct timerqueue_head	active;
	ktime_t			(*get_time)(void);
	ktime_t			offset;
} __attribute__((__aligned__(HRTIMER_CLOCK_BASE_ALIGN)));

enum  hrtimer_base_type {
	HRTIMER_BASE_MONOTONIC,
	HRTIMER_BASE_REALTIME,
	HRTIMER_BASE_BOOTTIME,
	HRTIMER_BASE_TAI,
	HRTIMER_MAX_CLOCK_BASES,
};

/*
 * struct hrtimer_cpu_base - the per cpu clock bases
 * @lock:		lock protecting the base and associated clock bases
 *			and timers
 * @seq:		seqcount around __run_hrtimer
 * @running:		pointer to the currently running hrtimer
 * @cpu:		cpu number
 * @active_bases:	Bitfield to mark bases with active timers
 * @clock_was_set_seq:	Sequence counter of clock was set events
 * @migration_enabled:	The migration of hrtimers to other cpus is enabled
 * @nohz_active:	The nohz functionality is enabled
 * @expires_next:	absolute time of the next event which was scheduled
 *			via clock_set_next_event()
 * @next_timer:		Pointer to the first expiring timer
 * @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
 *
 * 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;
	seqcount_t			seq;
	struct hrtimer			*running;
	unsigned int			cpu;
	unsigned int			active_bases;
	unsigned int			clock_was_set_seq;
	bool				migration_enabled;
	bool				nohz_active;
#ifdef CONFIG_HIGH_RES_TIMERS
	unsigned int			in_hrtirq	: 1,
					hres_active	: 1,
					hang_detected	: 1;
	ktime_t				expires_next;
	struct hrtimer			*next_timer;
	unsigned int			nr_events;
	unsigned int			nr_retries;
	unsigned int			nr_hangs;
	unsigned int			max_hang_time;
#endif
	struct hrtimer_clock_base	clock_base[HRTIMER_MAX_CLOCK_BASES];
} ____cacheline_aligned;

static inline void hrtimer_set_expires(struct hrtimer *timer, ktime_t time)
{
	BUILD_BUG_ON(sizeof(struct hrtimer_clock_base) > HRTIMER_CLOCK_BASE_ALIGN);

	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());
}

static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
{
	return timer->base->get_time();
}

#ifdef CONFIG_HIGH_RES_TIMERS
struct clock_event_device;

extern void hrtimer_interrupt(struct clock_event_device *dev);

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);

extern unsigned int hrtimer_resolution;

#else

# define MONOTONIC_RES_NSEC	LOW_RES_NSEC
# define KTIME_MONOTONIC_RES	KTIME_LOW_RES

#define hrtimer_resolution	(unsigned int)LOW_RES_NSEC

static inline void hrtimer_peek_ahead_timers(void) { }

static inline int hrtimer_is_hres_active(struct hrtimer *timer)
{
	return 0;
}

static inline void clock_was_set_delayed(void) { }

#endif

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.tv64 -= hrtimer_resolution;
	return rem;
}

static inline ktime_t
hrtimer_expires_remaining_adjusted(const struct hrtimer *timer)
{
	return __hrtimer_expires_remaining_adjusted(timer,
						    timer->base->get_time());
}

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);

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 void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
			unsigned long range_ns, const enum hrtimer_mode mode);

/**
 * hrtimer_start - (re)start an hrtimer on the current CPU
 * @timer:	the timer to be added
 * @tim:	expiry time
 * @mode:	expiry mode: absolute (HRTIMER_MODE_ABS) or
 *		relative (HRTIMER_MODE_REL)
 */
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)
{
	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));
	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 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->cpu_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 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);

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

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

#endif