linux/kernel/hrtimer.c
Thomas Gleixner c9db4fa115 [hrtimer] Enforce resolution as lower limit of intervals
Roman Zippel pointed out that the missing lower limit of intervals
leads to an accounting error in the overrun count. Enforce the lower
limit of intervals to resolution in the timer forwarding code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2006-01-12 11:47:34 +01:00

826 lines
18 KiB
C

/*
* 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, 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 (interval.tv64 < timer->base->resolution.tv64)
interval.tv64 = timer->base->resolution.tv64;
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 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;
}
/*
* Insert the timer to the rbtree and check whether it
* replaces the first pending timer
*/
rb_link_node(&timer->node, parent, link);
rb_insert_color(&timer->node, &base->active);
timer->state = HRTIMER_PENDING;
if (!base->first || timer->expires.tv64 <
rb_entry(base->first, struct hrtimer, node)->expires.tv64)
base->first = &timer->node;
}
/*
* __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 rbtree and replace the
* first entry pointer if necessary.
*/
if (base->first == &timer->node)
base->first = rb_next(&timer->node);
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;
bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
*tp = ktime_to_timespec(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();
struct rb_node *node;
spin_lock_irq(&base->lock);
while ((node = base->first)) {
struct hrtimer *timer;
int (*fn)(void *);
int restart;
void *data;
timer = rb_entry(node, struct hrtimer, node);
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 = &current_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);
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);
}