Commit c0a31329 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
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[PATCH] hrtimer: hrtimer core code



hrtimer subsystem core.  It is initialized at bootup and expired by the timer
interrupt, but is otherwise not utilized by any other subsystem yet.
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 97fc79f9
/*
* 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>
/*
* Mode arguments of xxx_hrtimer functions:
*/
enum hrtimer_mode {
HRTIMER_ABS, /* Time value is absolute */
HRTIMER_REL, /* Time value is relative to now */
};
enum hrtimer_restart {
HRTIMER_NORESTART,
HRTIMER_RESTART,
};
/*
* Timer states:
*/
enum hrtimer_state {
HRTIMER_INACTIVE, /* Timer is inactive */
HRTIMER_EXPIRED, /* Timer is expired */
HRTIMER_PENDING, /* Timer is pending */
};
struct hrtimer_base;
/**
* struct hrtimer - the basic hrtimer structure
*
* @node: red black tree node for time ordered insertion
* @list: list head for easier access to the time ordered list,
* without walking the red black tree.
* @expires: the absolute expiry time in the hrtimers internal
* representation. The time is related to the clock on
* which the timer is based.
* @state: state of the timer
* @function: timer expiry callback function
* @data: argument for the callback function
* @base: pointer to the timer base (per cpu and per clock)
*
* The hrtimer structure must be initialized by init_hrtimer_#CLOCKTYPE()
*/
struct hrtimer {
struct rb_node node;
struct list_head list;
ktime_t expires;
enum hrtimer_state state;
int (*function)(void *);
void *data;
struct hrtimer_base *base;
};
/**
* struct hrtimer_base - the timer base for a specific clock
*
* @index: clock type index for per_cpu support when moving a timer
* to a base on another cpu.
* @lock: lock protecting the base and associated timers
* @active: red black tree root node for the active timers
* @pending: list of pending timers for simple time ordered access
* @resolution: the resolution of the clock, in nanoseconds
* @get_time: function to retrieve the current time of the clock
* @curr_timer: the timer which is executing a callback right now
*/
struct hrtimer_base {
clockid_t index;
spinlock_t lock;
struct rb_root active;
struct list_head pending;
unsigned long resolution;
ktime_t (*get_time)(void);
struct hrtimer *curr_timer;
};
/* Exported timer functions: */
/* Initialize timers: */
extern void hrtimer_init(struct hrtimer *timer, const clockid_t which_clock);
extern void hrtimer_rebase(struct hrtimer *timer, const clockid_t which_clock);
/* Basic timer operations: */
extern int hrtimer_start(struct hrtimer *timer, ktime_t tim,
const enum hrtimer_mode mode);
extern int hrtimer_cancel(struct hrtimer *timer);
extern int hrtimer_try_to_cancel(struct hrtimer *timer);
#define hrtimer_restart(timer) hrtimer_start((timer), (timer)->expires, HRTIMER_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);
static inline int hrtimer_active(const struct hrtimer *timer)
{
return timer->state == HRTIMER_PENDING;
}
/* Forward a hrtimer so it expires after now: */
extern unsigned long hrtimer_forward(struct hrtimer *timer,
const ktime_t interval);
/* Soft interrupt function to run the hrtimer queues: */
extern void hrtimer_run_queues(void);
/* Bootup initialization: */
extern void __init hrtimers_init(void);
#endif
......@@ -266,4 +266,19 @@ static inline u64 ktime_to_ns(const ktime_t kt)
#endif
/*
* 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 KTIME_REALTIME_RES (NSEC_PER_SEC/HZ)
#define KTIME_MONOTONIC_RES (NSEC_PER_SEC/HZ)
/* Get the monotonic time in timespec format: */
extern void ktime_get_ts(struct timespec *ts);
/* Get the real (wall-) time in timespec format: */
#define ktime_get_real_ts(ts) getnstimeofday(ts)
#endif
......@@ -485,6 +485,7 @@ asmlinkage void __init start_kernel(void)
init_IRQ();
pidhash_init();
init_timers();
hrtimers_init();
softirq_init();
time_init();
......
......@@ -7,7 +7,8 @@ obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
sysctl.o capability.o ptrace.o timer.o user.o \
signal.o sys.o kmod.o workqueue.o pid.o \
rcupdate.o intermodule.o extable.o params.o posix-timers.o \
kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o
kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
hrtimer.o
obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o
obj-$(CONFIG_FUTEX) += futex.o
......
/*
* linux/kernel/hrtimer.c
*
* Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
* Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
*
* High-resolution kernel timers
*
* In contrast to the low-resolution timeout API implemented in
* kernel/timer.c, hrtimers provide finer resolution and accuracy
* depending on system configuration and capabilities.
*
* These timers are currently used for:
* - itimers
* - POSIX timers
* - nanosleep
* - precise in-kernel timing
*
* Started by: Thomas Gleixner and Ingo Molnar
*
* Credits:
* based on kernel/timer.c
*
* For licencing details see kernel-base/COPYING
*/
#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/hrtimer.h>
#include <linux/notifier.h>
#include <linux/syscalls.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
/**
* ktime_get - get the monotonic time in ktime_t format
*
* returns the time in ktime_t format
*/
static ktime_t ktime_get(void)
{
struct timespec now;
ktime_get_ts(&now);
return timespec_to_ktime(now);
}
/**
* ktime_get_real - get the real (wall-) time in ktime_t format
*
* returns the time in ktime_t format
*/
static ktime_t ktime_get_real(void)
{
struct timespec now;
getnstimeofday(&now);
return timespec_to_ktime(now);
}
EXPORT_SYMBOL_GPL(ktime_get_real);
/*
* The timer bases:
*/
#define MAX_HRTIMER_BASES 2
static DEFINE_PER_CPU(struct hrtimer_base, hrtimer_bases[MAX_HRTIMER_BASES]) =
{
{
.index = CLOCK_REALTIME,
.get_time = &ktime_get_real,
.resolution = KTIME_REALTIME_RES,
},
{
.index = CLOCK_MONOTONIC,
.get_time = &ktime_get,
.resolution = KTIME_MONOTONIC_RES,
},
};
/**
* ktime_get_ts - get the monotonic clock in timespec format
*
* @ts: pointer to timespec variable
*
* The function calculates the monotonic clock from the realtime
* clock and the wall_to_monotonic offset and stores the result
* in normalized timespec format in the variable pointed to by ts.
*/
void ktime_get_ts(struct timespec *ts)
{
struct timespec tomono;
unsigned long seq;
do {
seq = read_seqbegin(&xtime_lock);
getnstimeofday(ts);
tomono = wall_to_monotonic;
} while (read_seqretry(&xtime_lock, seq));
set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
ts->tv_nsec + tomono.tv_nsec);
}
/*
* Functions and macros which are different for UP/SMP systems are kept in a
* single place
*/
#ifdef CONFIG_SMP
#define set_curr_timer(b, t) do { (b)->curr_timer = (t); } while (0)
/*
* We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
* means that all timers which are tied to this base via timer->base are
* locked, and the base itself is locked too.
*
* So __run_timers/migrate_timers can safely modify all timers which could
* be found on the lists/queues.
*
* When the timer's base is locked, and the timer removed from list, it is
* possible to set timer->base = NULL and drop the lock: the timer remains
* locked.
*/
static struct hrtimer_base *lock_hrtimer_base(const struct hrtimer *timer,
unsigned long *flags)
{
struct hrtimer_base *base;
for (;;) {
base = timer->base;
if (likely(base != NULL)) {
spin_lock_irqsave(&base->lock, *flags);
if (likely(base == timer->base))
return base;
/* The timer has migrated to another CPU: */
spin_unlock_irqrestore(&base->lock, *flags);
}
cpu_relax();
}
}
/*
* Switch the timer base to the current CPU when possible.
*/
static inline struct hrtimer_base *
switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
{
struct hrtimer_base *new_base;
new_base = &__get_cpu_var(hrtimer_bases[base->index]);
if (base != new_base) {
/*
* We are trying to schedule the timer on the local CPU.
* However we can't change timer's base while it is running,
* so we keep it on the same CPU. No hassle vs. reprogramming
* the event source in the high resolution case. The softirq
* code will take care of this when the timer function has
* completed. There is no conflict as we hold the lock until
* the timer is enqueued.
*/
if (unlikely(base->curr_timer == timer))
return base;
/* See the comment in lock_timer_base() */
timer->base = NULL;
spin_unlock(&base->lock);
spin_lock(&new_base->lock);
timer->base = new_base;
}
return new_base;
}
#else /* CONFIG_SMP */
#define set_curr_timer(b, t) do { } while (0)
static inline struct hrtimer_base *
lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
{
struct hrtimer_base *base = timer->base;
spin_lock_irqsave(&base->lock, *flags);
return base;
}
#define switch_hrtimer_base(t, b) (b)
#endif /* !CONFIG_SMP */
/*
* Functions for the union type storage format of ktime_t which are
* too large for inlining:
*/
#if BITS_PER_LONG < 64
# ifndef CONFIG_KTIME_SCALAR
/**
* ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
*
* @kt: addend
* @nsec: the scalar nsec value to add
*
* Returns the sum of kt and nsec in ktime_t format
*/
ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
{
ktime_t tmp;
if (likely(nsec < NSEC_PER_SEC)) {
tmp.tv64 = nsec;
} else {
unsigned long rem = do_div(nsec, NSEC_PER_SEC);
tmp = ktime_set((long)nsec, rem);
}
return ktime_add(kt, tmp);
}
#else /* CONFIG_KTIME_SCALAR */
# endif /* !CONFIG_KTIME_SCALAR */
/*
* Divide a ktime value by a nanosecond value
*/
static unsigned long ktime_divns(const ktime_t kt, nsec_t div)
{
u64 dclc, inc, dns;
int sft = 0;
dclc = dns = ktime_to_ns(kt);
inc = div;
/* Make sure the divisor is less than 2^32: */
while (div >> 32) {
sft++;
div >>= 1;
}
dclc >>= sft;
do_div(dclc, (unsigned long) div);
return (unsigned long) dclc;
}
#else /* BITS_PER_LONG < 64 */
# define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
#endif /* BITS_PER_LONG >= 64 */
/*
* Counterpart to lock_timer_base above:
*/
static inline
void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
{
spin_unlock_irqrestore(&timer->base->lock, *flags);
}
/**
* hrtimer_forward - forward the timer expiry
*
* @timer: hrtimer to forward
* @interval: the interval to forward
*
* Forward the timer expiry so it will expire in the future.
* The number of overruns is added to the overrun field.
*/
unsigned long
hrtimer_forward(struct hrtimer *timer, const ktime_t interval)
{
unsigned long orun = 1;
ktime_t delta, now;
now = timer->base->get_time();
delta = ktime_sub(now, timer->expires);
if (delta.tv64 < 0)
return 0;
if (unlikely(delta.tv64 >= interval.tv64)) {
nsec_t incr = ktime_to_ns(interval);
orun = ktime_divns(delta, incr);
timer->expires = ktime_add_ns(timer->expires, incr * orun);
if (timer->expires.tv64 > now.tv64)
return orun;
/*
* This (and the ktime_add() below) is the
* correction for exact:
*/
orun++;
}
timer->expires = ktime_add(timer->expires, interval);
return orun;
}
/*
* enqueue_hrtimer - internal function to (re)start a timer
*
* The timer is inserted in expiry order. Insertion into the
* red black tree is O(log(n)). Must hold the base lock.
*/
static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
{
struct rb_node **link = &base->active.rb_node;
struct list_head *prev = &base->pending;
struct rb_node *parent = NULL;
struct hrtimer *entry;
/*
* Find the right place in the rbtree:
*/
while (*link) {
parent = *link;
entry = rb_entry(parent, struct hrtimer, node);
/*
* We dont care about collisions. Nodes with
* the same expiry time stay together.
*/
if (timer->expires.tv64 < entry->expires.tv64)
link = &(*link)->rb_left;
else {
link = &(*link)->rb_right;
prev = &entry->list;
}
}
/*
* Insert the timer to the rbtree and to the sorted list:
*/
rb_link_node(&timer->node, parent, link);
rb_insert_color(&timer->node, &base->active);
list_add(&timer->list, prev);
timer->state = HRTIMER_PENDING;
}
/*
* __remove_hrtimer - internal function to remove a timer
*
* Caller must hold the base lock.
*/
static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
{
/*
* Remove the timer from the sorted list and from the rbtree:
*/
list_del(&timer->list);
rb_erase(&timer->node, &base->active);
}
/*
* remove hrtimer, called with base lock held
*/
static inline int
remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
{
if (hrtimer_active(timer)) {
__remove_hrtimer(timer, base);
timer->state = HRTIMER_INACTIVE;
return 1;
}
return 0;
}
/**
* hrtimer_start - (re)start an relative timer on the current CPU
*
* @timer: the timer to be added
* @tim: expiry time
* @mode: expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
*
* Returns:
* 0 on success
* 1 when the timer was active
*/
int
hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
{
struct hrtimer_base *base, *new_base;
unsigned long flags;
int ret;
base = lock_hrtimer_base(timer, &flags);
/* Remove an active timer from the queue: */
ret = remove_hrtimer(timer, base);
/* Switch the timer base, if necessary: */
new_base = switch_hrtimer_base(timer, base);
if (mode == HRTIMER_REL)
tim = ktime_add(tim, new_base->get_time());
timer->expires = tim;
enqueue_hrtimer(timer, new_base);
unlock_hrtimer_base(timer, &flags);
return ret;
}
/**
* hrtimer_try_to_cancel - try to deactivate a timer
*
* @timer: hrtimer to stop
*
* Returns:
* 0 when the timer was not active
* 1 when the timer was active
* -1 when the timer is currently excuting the callback function and
* can not be stopped
*/
int hrtimer_try_to_cancel(struct hrtimer *timer)
{
struct hrtimer_base *base;
unsigned long flags;
int ret = -1;
base = lock_hrtimer_base(timer, &flags);
if (base->curr_timer != timer)
ret = remove_hrtimer(timer, base);
unlock_hrtimer_base(timer, &flags);
return ret;
}
/**
* hrtimer_cancel - cancel a timer and wait for the handler to finish.
*
* @timer: the timer to be cancelled
*
* Returns:
* 0 when the timer was not active
* 1 when the timer was active
*/
int hrtimer_cancel(struct hrtimer *timer)
{
for (;;) {
int ret = hrtimer_try_to_cancel(timer);
if (ret >= 0)
return ret;
}
}
/**
* hrtimer_get_remaining - get remaining time for the timer
*
* @timer: the timer to read
*/
ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
{
struct hrtimer_base *base;
unsigned long flags;