/*
* 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);
}
EXPORT_SYMBOL_GPL(ktime_get_ts);
/*
* 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;
ktime_t rem;
base = lock_hrtimer_base(timer, &flags);
rem = ktime_sub(timer->expires, timer->base->get_time());
unlock_hrtimer_base(timer, &flags);
return rem;
}
/**
* hrtimer_rebase - rebase an initialized hrtimer to a different base
*
* @timer: the timer to be rebased
* @clock_id: the clock to be used
*/
void hrtimer_rebase(struct hrtimer *timer, const clockid_t clock_id)
{
struct hrtimer_base *bases;
bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
timer->base = &bases[clock_id];
}
/**
* hrtimer_init - initialize a timer to the given clock
*
* @timer: the timer to be initialized
* @clock_id: the clock to be used
*/
void hrtimer_init(struct hrtimer *timer, const clockid_t clock_id)
{
memset(timer, 0, sizeof(struct hrtimer));
hrtimer_rebase(timer, clock_id);
}
/**
* hrtimer_get_res - get the timer resolution for a clock
*
* @which_clock: which clock to query
* @tp: pointer to timespec variable to store the resolution
*
* Store the resolution of the clock selected by which_clock in the
* variable pointed to by tp.
*/
int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
{
struct hrtimer_base *bases;
tp->tv_sec = 0;
bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
tp->tv_nsec = bases[which_clock].resolution;
return 0;
}
/*
* Expire the per base hrtimer-queue:
*/
static inline void run_hrtimer_queue(struct hrtimer_base *base)
{
ktime_t now = base->get_time();
spin_lock_irq(&base->lock);
while (!list_empty(&base->pending)) {
struct hrtimer *timer;
int (*fn)(void *);
int restart;
void *data;
timer = list_entry(base->pending.next, struct hrtimer, list);
if (now.tv64 <= timer->expires.tv64)
break;
fn = timer->function;
data = timer->data;
set_curr_timer(base, timer);
__remove_hrtimer(timer, base);
spin_unlock_irq(&base->lock);
/*
* fn == NULL is special case for the simplest timer
* variant - wake up process and do not restart:
*/
if (!fn) {
wake_up_process(data);
restart = HRTIMER_NORESTART;
} else
restart = fn(data);
spin_lock_irq(&base->lock);
if (restart == HRTIMER_RESTART)
enqueue_hrtimer(timer, base);
else
timer->state = HRTIMER_EXPIRED;
}
set_curr_timer(base, NULL);
spin_unlock_irq(&base->lock);
}
/*
* Called from timer softirq every jiffy, expire hrtimers:
*/
void hrtimer_run_queues(void)
{
struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
int i;
for (i = 0; i < MAX_HRTIMER_BASES; i++)
run_hrtimer_queue(&base[i]);
}
/*
* Sleep related functions:
*/
/**
* schedule_hrtimer - sleep until timeout
*
* @timer: hrtimer variable initialized with the correct clock base
* @mode: timeout value is abs/rel
*
* Make the current task sleep until @timeout is
* elapsed.
*
* You can set the task state as follows -
*
* %TASK_UNINTERRUPTIBLE - at least @timeout is guaranteed to
* pass before the routine returns. The routine will return 0
*
* %TASK_INTERRUPTIBLE - the routine may return early if a signal is
* delivered to the current task. In this case the remaining time
* will be returned
*
* The current task state is guaranteed to be TASK_RUNNING when this
* routine returns.
*/
static ktime_t __sched
schedule_hrtimer(struct hrtimer *timer, const enum hrtimer_mode mode)
{
/* fn stays NULL, meaning single-shot wakeup: */
timer->data = current;
hrtimer_start(timer, timer->expires, mode);
schedule();
hrtimer_cancel(timer);
/* Return the remaining time: */
if (timer->state != HRTIMER_EXPIRED)
return ktime_sub(timer->expires, timer->base->get_time());
else
return (ktime_t) {.tv64 = 0 };
}
static inline ktime_t __sched
schedule_hrtimer_interruptible(struct hrtimer *timer,
const enum hrtimer_mode mode)
{
set_current_state(TASK_INTERRUPTIBLE);
return schedule_hrtimer(timer, mode);
}
static long __sched
nanosleep_restart(struct restart_block *restart, clockid_t clockid)
{
struct timespec __user *rmtp, tu;
void *rfn_save = restart->fn;
struct hrtimer timer;
ktime_t rem;
restart->fn = do_no_restart_syscall;
hrtimer_init(&timer, clockid);
timer.expires.tv64 = ((u64)restart->arg1 << 32) | (u64) restart->arg0;
rem = schedule_hrtimer_interruptible(&timer, HRTIMER_ABS);
if (rem.tv64 <= 0)
return 0;
rmtp = (struct timespec __user *) restart->arg2;
tu = ktime_to_timespec(rem);
if (rmtp && copy_to_user(rmtp, &tu, sizeof(tu)))
return -EFAULT;
restart->fn = rfn_save;
/* The other values in restart are already filled in */
return -ERESTART_RESTARTBLOCK;
}
static long __sched nanosleep_restart_mono(struct restart_block *restart)
{
return nanosleep_restart(restart, CLOCK_MONOTONIC);
}
static long __sched nanosleep_restart_real(struct restart_block *restart)
{
return nanosleep_restart(restart, CLOCK_REALTIME);
}
long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
const enum hrtimer_mode mode, const clockid_t clockid)
{
struct restart_block *restart;
struct hrtimer timer;
struct timespec tu;
ktime_t rem;
hrtimer_init(&timer, clockid);
timer.expires = timespec_to_ktime(*rqtp);
rem = schedule_hrtimer_interruptible(&timer, mode);
if (rem.tv64 <= 0)
return 0;
/* Absolute timers do not update the rmtp value: */
if (mode == HRTIMER_ABS)
return -ERESTARTNOHAND;
tu = ktime_to_timespec(rem);
if (rmtp && copy_to_user(rmtp, &tu, sizeof(tu)))
return -EFAULT;
restart = ¤t_thread_info()->restart_block;
restart->fn = (clockid == CLOCK_MONOTONIC) ?
nanosleep_restart_mono : nanosleep_restart_real;
restart->arg0 = timer.expires.tv64 & 0xFFFFFFFF;
restart->arg1 = timer.expires.tv64 >> 32;
restart->arg2 = (unsigned long) rmtp;
return -ERESTART_RESTARTBLOCK;
}
asmlinkage long
sys_nanosleep(struct timespec __user *rqtp, struct timespec __user *rmtp)
{
struct timespec tu;
if (copy_from_user(&tu, rqtp, sizeof(tu)))
return -EFAULT;
if (!timespec_valid(&tu))
return -EINVAL;
return hrtimer_nanosleep(&tu, rmtp, HRTIMER_REL, CLOCK_MONOTONIC);
}
/*
* Functions related to boot-time initialization:
*/
static void __devinit init_hrtimers_cpu(int cpu)
{
struct hrtimer_base *base = per_cpu(hrtimer_bases, cpu);
int i;
for (i = 0; i < MAX_HRTIMER_BASES; i++) {
spin_lock_init(&base->lock);
INIT_LIST_HEAD(&base->pending);
base++;
}
}
#ifdef CONFIG_HOTPLUG_CPU
static void migrate_hrtimer_list(struct hrtimer_base *old_base,
struct hrtimer_base *new_base)
{
struct hrtimer *timer;
struct rb_node *node;
while ((node = rb_first(&old_base->active))) {
timer = rb_entry(node, struct hrtimer, node);
__remove_hrtimer(timer, old_base);
timer->base = new_base;
enqueue_hrtimer(timer, new_base);
}
}
static void migrate_hrtimers(int cpu)
{
struct hrtimer_base *old_base, *new_base;
int i;
BUG_ON(cpu_online(cpu));
old_base = per_cpu(hrtimer_bases, cpu);
new_base = get_cpu_var(hrtimer_bases);
local_irq_disable();
for (i = 0; i < MAX_HRTIMER_BASES; i++) {
spin_lock(&new_base->lock);
spin_lock(&old_base->lock);
BUG_ON(old_base->curr_timer);
migrate_hrtimer_list(old_base, new_base);
spin_unlock(&old_base->lock);
spin_unlock(&new_base->lock);
old_base++;
new_base++;
}
local_irq_enable();
put_cpu_var(hrtimer_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */
static int __devinit hrtimer_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
long cpu = (long)hcpu;
switch (action) {
case CPU_UP_PREPARE:
init_hrtimers_cpu(cpu);
break;
#ifdef CONFIG_HOTPLUG_CPU
case CPU_DEAD:
migrate_hrtimers(cpu);
break;
#endif
default:
break;
}
return NOTIFY_OK;
}
static struct notifier_block __devinitdata hrtimers_nb = {
.notifier_call = hrtimer_cpu_notify,
};
void __init hrtimers_init(void)
{
hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
(void *)(long)smp_processor_id());
register_cpu_notifier(&hrtimers_nb);
}
