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linux/kernel/timer.c
Oleg Nesterov a2c348fe01 [PATCH] __mod_timer: simplify ->base changing 
Since base and new_base are of the same type now, we can save one 'if'
branch and simplify the code a bit.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-31 12:18:53 -08:00

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/*
* linux/kernel/timer.c
*
* Kernel internal timers, kernel timekeeping, basic process system calls
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* 1997-01-28 Modified by Finn Arne Gangstad to make timers scale better.
*
* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
* "A Kernel Model for Precision Timekeeping" by Dave Mills
* 1998-12-24 Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
* serialize accesses to xtime/lost_ticks).
* Copyright (C) 1998 Andrea Arcangeli
* 1999-03-10 Improved NTP compatibility by Ulrich Windl
* 2002-05-31 Move sys_sysinfo here and make its locking sane, Robert Love
* 2000-10-05 Implemented scalable SMP per-CPU timer handling.
* Copyright (C) 2000, 2001, 2002 Ingo Molnar
* Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
*/
#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/notifier.h>
#include <linux/thread_info.h>
#include <linux/time.h>
#include <linux/jiffies.h>
#include <linux/posix-timers.h>
#include <linux/cpu.h>
#include <linux/syscalls.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/div64.h>
#include <asm/timex.h>
#include <asm/io.h>
#ifdef CONFIG_TIME_INTERPOLATION
static void time_interpolator_update(long delta_nsec);
#else
#define time_interpolator_update(x)
#endif
u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
EXPORT_SYMBOL(jiffies_64);
/*
* per-CPU timer vector definitions:
*/
#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
#define TVN_SIZE (1 << TVN_BITS)
#define TVR_SIZE (1 << TVR_BITS)
#define TVN_MASK (TVN_SIZE - 1)
#define TVR_MASK (TVR_SIZE - 1)
typedef struct tvec_s {
struct list_head vec[TVN_SIZE];
} tvec_t;
typedef struct tvec_root_s {
struct list_head vec[TVR_SIZE];
} tvec_root_t;
struct tvec_t_base_s {
spinlock_t lock;
struct timer_list *running_timer;
unsigned long timer_jiffies;
tvec_root_t tv1;
tvec_t tv2;
tvec_t tv3;
tvec_t tv4;
tvec_t tv5;
} ____cacheline_aligned_in_smp;
typedef struct tvec_t_base_s tvec_base_t;
static DEFINE_PER_CPU(tvec_base_t *, tvec_bases);
tvec_base_t boot_tvec_bases;
EXPORT_SYMBOL(boot_tvec_bases);
static inline void set_running_timer(tvec_base_t *base,
struct timer_list *timer)
{
#ifdef CONFIG_SMP
base->running_timer = timer;
#endif
}
static void internal_add_timer(tvec_base_t *base, struct timer_list *timer)
{
unsigned long expires = timer->expires;
unsigned long idx = expires - base->timer_jiffies;
struct list_head *vec;
if (idx < TVR_SIZE) {
int i = expires & TVR_MASK;
vec = base->tv1.vec + i;
} else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
int i = (expires >> TVR_BITS) & TVN_MASK;
vec = base->tv2.vec + i;
} else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
vec = base->tv3.vec + i;
} else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
vec = base->tv4.vec + i;
} else if ((signed long) idx < 0) {
/*
* Can happen if you add a timer with expires == jiffies,
* or you set a timer to go off in the past
*/
vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK);
} else {
int i;
/* If the timeout is larger than 0xffffffff on 64-bit
* architectures then we use the maximum timeout:
*/
if (idx > 0xffffffffUL) {
idx = 0xffffffffUL;
expires = idx + base->timer_jiffies;
}
i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
vec = base->tv5.vec + i;
}
/*
* Timers are FIFO:
*/
list_add_tail(&timer->entry, vec);
}
/***
* init_timer - initialize a timer.
* @timer: the timer to be initialized
*
* init_timer() must be done to a timer prior calling *any* of the
* other timer functions.
*/
void fastcall init_timer(struct timer_list *timer)
{
timer->entry.next = NULL;
timer->base = per_cpu(tvec_bases, raw_smp_processor_id());
}
EXPORT_SYMBOL(init_timer);
static inline void detach_timer(struct timer_list *timer,
int clear_pending)
{
struct list_head *entry = &timer->entry;
__list_del(entry->prev, entry->next);
if (clear_pending)
entry->next = NULL;
entry->prev = LIST_POISON2;
}
/*
* We are using hashed locking: holding per_cpu(tvec_bases).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 ->tvX lists.
*
* 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 tvec_base_t *lock_timer_base(struct timer_list *timer,
unsigned long *flags)
{
tvec_base_t *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();
}
}
int __mod_timer(struct timer_list *timer, unsigned long expires)
{
tvec_base_t *base, *new_base;
unsigned long flags;
int ret = 0;
BUG_ON(!timer->function);
base = lock_timer_base(timer, &flags);
if (timer_pending(timer)) {
detach_timer(timer, 0);
ret = 1;
}
new_base = __get_cpu_var(tvec_bases);
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,
* otherwise del_timer_sync() can't detect that the timer's
* handler yet has not finished. This also guarantees that
* the timer is serialized wrt itself.
*/
if (likely(base->running_timer != timer)) {
/* See the comment in lock_timer_base() */
timer->base = NULL;
spin_unlock(&base->lock);
base = new_base;
spin_lock(&base->lock);
timer->base = base;
}
}
timer->expires = expires;
internal_add_timer(base, timer);
spin_unlock_irqrestore(&base->lock, flags);
return ret;
}
EXPORT_SYMBOL(__mod_timer);
/***
* add_timer_on - start a timer on a particular CPU
* @timer: the timer to be added
* @cpu: the CPU to start it on
*
* This is not very scalable on SMP. Double adds are not possible.
*/
void add_timer_on(struct timer_list *timer, int cpu)
{
tvec_base_t *base = per_cpu(tvec_bases, cpu);
unsigned long flags;
BUG_ON(timer_pending(timer) || !timer->function);
spin_lock_irqsave(&base->lock, flags);
timer->base = base;
internal_add_timer(base, timer);
spin_unlock_irqrestore(&base->lock, flags);
}
/***
* mod_timer - modify a timer's timeout
* @timer: the timer to be modified
*
* mod_timer is a more efficient way to update the expire field of an
* active timer (if the timer is inactive it will be activated)
*
* mod_timer(timer, expires) is equivalent to:
*
* del_timer(timer); timer->expires = expires; add_timer(timer);
*
* Note that if there are multiple unserialized concurrent users of the
* same timer, then mod_timer() is the only safe way to modify the timeout,
* since add_timer() cannot modify an already running timer.
*
* The function returns whether it has modified a pending timer or not.
* (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
* active timer returns 1.)
*/
int mod_timer(struct timer_list *timer, unsigned long expires)
{
BUG_ON(!timer->function);
/*
* This is a common optimization triggered by the
* networking code - if the timer is re-modified
* to be the same thing then just return:
*/
if (timer->expires == expires && timer_pending(timer))
return 1;
return __mod_timer(timer, expires);
}
EXPORT_SYMBOL(mod_timer);
/***
* del_timer - deactive a timer.
* @timer: the timer to be deactivated
*
* del_timer() deactivates a timer - this works on both active and inactive
* timers.
*
* The function returns whether it has deactivated a pending timer or not.
* (ie. del_timer() of an inactive timer returns 0, del_timer() of an
* active timer returns 1.)
*/
int del_timer(struct timer_list *timer)
{
tvec_base_t *base;
unsigned long flags;
int ret = 0;
if (timer_pending(timer)) {
base = lock_timer_base(timer, &flags);
if (timer_pending(timer)) {
detach_timer(timer, 1);
ret = 1;
}
spin_unlock_irqrestore(&base->lock, flags);
}
return ret;
}
EXPORT_SYMBOL(del_timer);
#ifdef CONFIG_SMP
/*
* This function tries to deactivate a timer. Upon successful (ret >= 0)
* exit the timer is not queued and the handler is not running on any CPU.
*
* It must not be called from interrupt contexts.
*/
int try_to_del_timer_sync(struct timer_list *timer)
{
tvec_base_t *base;
unsigned long flags;
int ret = -1;
base = lock_timer_base(timer, &flags);
if (base->running_timer == timer)
goto out;
ret = 0;
if (timer_pending(timer)) {
detach_timer(timer, 1);
ret = 1;
}
out:
spin_unlock_irqrestore(&base->lock, flags);
return ret;
}
/***
* del_timer_sync - deactivate a timer and wait for the handler to finish.
* @timer: the timer to be deactivated
*
* This function only differs from del_timer() on SMP: besides deactivating
* the timer it also makes sure the handler has finished executing on other
* CPUs.
*
* Synchronization rules: callers must prevent restarting of the timer,
* otherwise this function is meaningless. It must not be called from
* interrupt contexts. The caller must not hold locks which would prevent
* completion of the timer's handler. The timer's handler must not call
* add_timer_on(). Upon exit the timer is not queued and the handler is
* not running on any CPU.
*
* The function returns whether it has deactivated a pending timer or not.
*/
int del_timer_sync(struct timer_list *timer)
{
for (;;) {
int ret = try_to_del_timer_sync(timer);
if (ret >= 0)
return ret;
}
}
EXPORT_SYMBOL(del_timer_sync);
#endif
static int cascade(tvec_base_t *base, tvec_t *tv, int index)
{
/* cascade all the timers from tv up one level */
struct list_head *head, *curr;
head = tv->vec + index;
curr = head->next;
/*
* We are removing _all_ timers from the list, so we don't have to
* detach them individually, just clear the list afterwards.
*/
while (curr != head) {
struct timer_list *tmp;
tmp = list_entry(curr, struct timer_list, entry);
BUG_ON(tmp->base != base);
curr = curr->next;
internal_add_timer(base, tmp);
}
INIT_LIST_HEAD(head);
return index;
}
/***
* __run_timers - run all expired timers (if any) on this CPU.
* @base: the timer vector to be processed.
*
* This function cascades all vectors and executes all expired timer
* vectors.
*/
#define INDEX(N) (base->timer_jiffies >> (TVR_BITS + N * TVN_BITS)) & TVN_MASK
static inline void __run_timers(tvec_base_t *base)
{
struct timer_list *timer;
spin_lock_irq(&base->lock);
while (time_after_eq(jiffies, base->timer_jiffies)) {
struct list_head work_list = LIST_HEAD_INIT(work_list);
struct list_head *head = &work_list;
int index = base->timer_jiffies & TVR_MASK;
/*
* Cascade timers:
*/
if (!index &&
(!cascade(base, &base->tv2, INDEX(0))) &&
(!cascade(base, &base->tv3, INDEX(1))) &&
!cascade(base, &base->tv4, INDEX(2)))
cascade(base, &base->tv5, INDEX(3));
++base->timer_jiffies;
list_splice_init(base->tv1.vec + index, &work_list);
while (!list_empty(head)) {
void (*fn)(unsigned long);
unsigned long data;
timer = list_entry(head->next,struct timer_list,entry);
fn = timer->function;
data = timer->data;
set_running_timer(base, timer);
detach_timer(timer, 1);
spin_unlock_irq(&base->lock);
{
int preempt_count = preempt_count();
fn(data);
if (preempt_count != preempt_count()) {
printk(KERN_WARNING "huh, entered %p "
"with preempt_count %08x, exited"
" with %08x?\n",
fn, preempt_count,
preempt_count());
BUG();
}
}
spin_lock_irq(&base->lock);
}
}
set_running_timer(base, NULL);
spin_unlock_irq(&base->lock);
}
#ifdef CONFIG_NO_IDLE_HZ
/*
* Find out when the next timer event is due to happen. This
* is used on S/390 to stop all activity when a cpus is idle.
* This functions needs to be called disabled.
*/
unsigned long next_timer_interrupt(void)
{
tvec_base_t *base;
struct list_head *list;
struct timer_list *nte;
unsigned long expires;
unsigned long hr_expires = MAX_JIFFY_OFFSET;
ktime_t hr_delta;
tvec_t *varray[4];
int i, j;
hr_delta = hrtimer_get_next_event();
if (hr_delta.tv64 != KTIME_MAX) {
struct timespec tsdelta;
tsdelta = ktime_to_timespec(hr_delta);
hr_expires = timespec_to_jiffies(&tsdelta);
if (hr_expires < 3)
return hr_expires + jiffies;
}
hr_expires += jiffies;
base = __get_cpu_var(tvec_bases);
spin_lock(&base->lock);
expires = base->timer_jiffies + (LONG_MAX >> 1);
list = NULL;
/* Look for timer events in tv1. */
j = base->timer_jiffies & TVR_MASK;
do {
list_for_each_entry(nte, base->tv1.vec + j, entry) {
expires = nte->expires;
if (j < (base->timer_jiffies & TVR_MASK))
list = base->tv2.vec + (INDEX(0));
goto found;
}
j = (j + 1) & TVR_MASK;
} while (j != (base->timer_jiffies & TVR_MASK));
/* Check tv2-tv5. */
varray[0] = &base->tv2;
varray[1] = &base->tv3;
varray[2] = &base->tv4;
varray[3] = &base->tv5;
for (i = 0; i < 4; i++) {
j = INDEX(i);
do {
if (list_empty(varray[i]->vec + j)) {
j = (j + 1) & TVN_MASK;
continue;
}
list_for_each_entry(nte, varray[i]->vec + j, entry)
if (time_before(nte->expires, expires))
expires = nte->expires;
if (j < (INDEX(i)) && i < 3)
list = varray[i + 1]->vec + (INDEX(i + 1));
goto found;
} while (j != (INDEX(i)));
}
found:
if (list) {
/*
* The search wrapped. We need to look at the next list
* from next tv element that would cascade into tv element
* where we found the timer element.
*/
list_for_each_entry(nte, list, entry) {
if (time_before(nte->expires, expires))
expires = nte->expires;
}
}
spin_unlock(&base->lock);
if (time_before(hr_expires, expires))
return hr_expires;
return expires;
}
#endif
/******************************************************************/
/*
* Timekeeping variables
*/
unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */
unsigned long tick_nsec = TICK_NSEC; /* ACTHZ period (nsec) */
/*
* The current time
* wall_to_monotonic is what we need to add to xtime (or xtime corrected
* for sub jiffie times) to get to monotonic time. Monotonic is pegged
* at zero at system boot time, so wall_to_monotonic will be negative,
* however, we will ALWAYS keep the tv_nsec part positive so we can use
* the usual normalization.
*/
struct timespec xtime __attribute__ ((aligned (16)));
struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
EXPORT_SYMBOL(xtime);
/* Don't completely fail for HZ > 500. */
int tickadj = 500/HZ ? : 1; /* microsecs */
/*
* phase-lock loop variables
*/
/* TIME_ERROR prevents overwriting the CMOS clock */
int time_state = TIME_OK; /* clock synchronization status */
int time_status = STA_UNSYNC; /* clock status bits */
long time_offset; /* time adjustment (us) */
long time_constant = 2; /* pll time constant */
long time_tolerance = MAXFREQ; /* frequency tolerance (ppm) */
long time_precision = 1; /* clock precision (us) */
long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */
long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */
static long time_phase; /* phase offset (scaled us) */
long time_freq = (((NSEC_PER_SEC + HZ/2) % HZ - HZ/2) << SHIFT_USEC) / NSEC_PER_USEC;
/* frequency offset (scaled ppm)*/
static long time_adj; /* tick adjust (scaled 1 / HZ) */
long time_reftime; /* time at last adjustment (s) */
long time_adjust;
long time_next_adjust;
/*
* this routine handles the overflow of the microsecond field
*
* The tricky bits of code to handle the accurate clock support
* were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
* They were originally developed for SUN and DEC kernels.
* All the kudos should go to Dave for this stuff.
*
*/
static void second_overflow(void)
{
long ltemp;
/* Bump the maxerror field */
time_maxerror += time_tolerance >> SHIFT_USEC;
if (time_maxerror > NTP_PHASE_LIMIT) {
time_maxerror = NTP_PHASE_LIMIT;
time_status |= STA_UNSYNC;
}
/*
* Leap second processing. If in leap-insert state at the end of the
* day, the system clock is set back one second; if in leap-delete
* state, the system clock is set ahead one second. The microtime()
* routine or external clock driver will insure that reported time is
* always monotonic. The ugly divides should be replaced.
*/
switch (time_state) {
case TIME_OK:
if (time_status & STA_INS)
time_state = TIME_INS;
else if (time_status & STA_DEL)
time_state = TIME_DEL;
break;
case TIME_INS:
if (xtime.tv_sec % 86400 == 0) {
xtime.tv_sec--;
wall_to_monotonic.tv_sec++;
/*
* The timer interpolator will make time change
* gradually instead of an immediate jump by one second
*/
time_interpolator_update(-NSEC_PER_SEC);
time_state = TIME_OOP;
clock_was_set();
printk(KERN_NOTICE "Clock: inserting leap second "
"23:59:60 UTC\n");
}
break;
case TIME_DEL:
if ((xtime.tv_sec + 1) % 86400 == 0) {
xtime.tv_sec++;
wall_to_monotonic.tv_sec--;
/*
* Use of time interpolator for a gradual change of
* time
*/
time_interpolator_update(NSEC_PER_SEC);
time_state = TIME_WAIT;
clock_was_set();
printk(KERN_NOTICE "Clock: deleting leap second "
"23:59:59 UTC\n");
}
break;
case TIME_OOP:
time_state = TIME_WAIT;
break;
case TIME_WAIT:
if (!(time_status & (STA_INS | STA_DEL)))
time_state = TIME_OK;
}
/*
* Compute the phase adjustment for the next second. In PLL mode, the
* offset is reduced by a fixed factor times the time constant. In FLL
* mode the offset is used directly. In either mode, the maximum phase
* adjustment for each second is clamped so as to spread the adjustment
* over not more than the number of seconds between updates.
*/
ltemp = time_offset;
if (!(time_status & STA_FLL))
ltemp = shift_right(ltemp, SHIFT_KG + time_constant);
ltemp = min(ltemp, (MAXPHASE / MINSEC) << SHIFT_UPDATE);
ltemp = max(ltemp, -(MAXPHASE / MINSEC) << SHIFT_UPDATE);
time_offset -= ltemp;
time_adj = ltemp << (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
/*
* Compute the frequency estimate and additional phase adjustment due
* to frequency error for the next second.
*/
ltemp = time_freq;
time_adj += shift_right(ltemp,(SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE));
#if HZ == 100
/*
* Compensate for (HZ==100) != (1 << SHIFT_HZ). Add 25% and 3.125% to
* get 128.125; => only 0.125% error (p. 14)
*/
time_adj += shift_right(time_adj, 2) + shift_right(time_adj, 5);
#endif
#if HZ == 250
/*
* Compensate for (HZ==250) != (1 << SHIFT_HZ). Add 1.5625% and
* 0.78125% to get 255.85938; => only 0.05% error (p. 14)
*/
time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
#endif
#if HZ == 1000
/*
* Compensate for (HZ==1000) != (1 << SHIFT_HZ). Add 1.5625% and
* 0.78125% to get 1023.4375; => only 0.05% error (p. 14)
*/
time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
#endif
}
/*
* Returns how many microseconds we need to add to xtime this tick
* in doing an adjustment requested with adjtime.
*/
static long adjtime_adjustment(void)
{
long time_adjust_step;
time_adjust_step = time_adjust;
if (time_adjust_step) {
/*
* We are doing an adjtime thing. Prepare time_adjust_step to
* be within bounds. Note that a positive time_adjust means we
* want the clock to run faster.
*
* Limit the amount of the step to be in the range
* -tickadj .. +tickadj
*/
time_adjust_step = min(time_adjust_step, (long)tickadj);
time_adjust_step = max(time_adjust_step, (long)-tickadj);
}
return time_adjust_step;
}
/* in the NTP reference this is called "hardclock()" */
static void update_wall_time_one_tick(void)
{
long time_adjust_step, delta_nsec;
time_adjust_step = adjtime_adjustment();
if (time_adjust_step)
/* Reduce by this step the amount of time left */
time_adjust -= time_adjust_step;
delta_nsec = tick_nsec + time_adjust_step * 1000;
/*
* Advance the phase, once it gets to one microsecond, then
* advance the tick more.
*/
time_phase += time_adj;
if ((time_phase >= FINENSEC) || (time_phase <= -FINENSEC)) {
long ltemp = shift_right(time_phase, (SHIFT_SCALE - 10));
time_phase -= ltemp << (SHIFT_SCALE - 10);
delta_nsec += ltemp;
}
xtime.tv_nsec += delta_nsec;
time_interpolator_update(delta_nsec);
/* Changes by adjtime() do not take effect till next tick. */
if (time_next_adjust != 0) {
time_adjust = time_next_adjust;
time_next_adjust = 0;
}
}
/*
* Return how long ticks are at the moment, that is, how much time
* update_wall_time_one_tick will add to xtime next time we call it
* (assuming no calls to do_adjtimex in the meantime).
* The return value is in fixed-point nanoseconds with SHIFT_SCALE-10
* bits to the right of the binary point.
* This function has no side-effects.
*/
u64 current_tick_length(void)
{
long delta_nsec;
delta_nsec = tick_nsec + adjtime_adjustment() * 1000;
return ((u64) delta_nsec << (SHIFT_SCALE - 10)) + time_adj;
}
/*
* Using a loop looks inefficient, but "ticks" is
* usually just one (we shouldn't be losing ticks,
* we're doing this this way mainly for interrupt
* latency reasons, not because we think we'll
* have lots of lost timer ticks
*/
static void update_wall_time(unsigned long ticks)
{
do {
ticks--;
update_wall_time_one_tick();
if (xtime.tv_nsec >= 1000000000) {
xtime.tv_nsec -= 1000000000;
xtime.tv_sec++;
second_overflow();
}
} while (ticks);
}
/*
* Called from the timer interrupt handler to charge one tick to the current
* process. user_tick is 1 if the tick is user time, 0 for system.
*/
void update_process_times(int user_tick)
{
struct task_struct *p = current;
int cpu = smp_processor_id();
/* Note: this timer irq context must be accounted for as well. */
if (user_tick)
account_user_time(p, jiffies_to_cputime(1));
else
account_system_time(p, HARDIRQ_OFFSET, jiffies_to_cputime(1));
run_local_timers();
if (rcu_pending(cpu))
rcu_check_callbacks(cpu, user_tick);
scheduler_tick();
run_posix_cpu_timers(p);
}
/*
* Nr of active tasks - counted in fixed-point numbers
*/
static unsigned long count_active_tasks(void)
{
return (nr_running() + nr_uninterruptible()) * FIXED_1;
}
/*
* Hmm.. Changed this, as the GNU make sources (load.c) seems to
* imply that avenrun[] is the standard name for this kind of thing.
* Nothing else seems to be standardized: the fractional size etc
* all seem to differ on different machines.
*
* Requires xtime_lock to access.
*/
unsigned long avenrun[3];
EXPORT_SYMBOL(avenrun);
/*
* calc_load - given tick count, update the avenrun load estimates.
* This is called while holding a write_lock on xtime_lock.
*/
static inline void calc_load(unsigned long ticks)
{
unsigned long active_tasks; /* fixed-point */
static int count = LOAD_FREQ;
count -= ticks;
if (count < 0) {
count += LOAD_FREQ;
active_tasks = count_active_tasks();
CALC_LOAD(avenrun[0], EXP_1, active_tasks);
CALC_LOAD(avenrun[1], EXP_5, active_tasks);
CALC_LOAD(avenrun[2], EXP_15, active_tasks);
}
}
/* jiffies at the most recent update of wall time */
unsigned long wall_jiffies = INITIAL_JIFFIES;
/*
* This read-write spinlock protects us from races in SMP while
* playing with xtime and avenrun.
*/
#ifndef ARCH_HAVE_XTIME_LOCK
seqlock_t xtime_lock __cacheline_aligned_in_smp = SEQLOCK_UNLOCKED;
EXPORT_SYMBOL(xtime_lock);
#endif
/*
* This function runs timers and the timer-tq in bottom half context.
*/
static void run_timer_softirq(struct softirq_action *h)
{
tvec_base_t *base = __get_cpu_var(tvec_bases);
hrtimer_run_queues();
if (time_after_eq(jiffies, base->timer_jiffies))
__run_timers(base);
}
/*
* Called by the local, per-CPU timer interrupt on SMP.
*/
void run_local_timers(void)
{
raise_softirq(TIMER_SOFTIRQ);
softlockup_tick();
}
/*
* Called by the timer interrupt. xtime_lock must already be taken
* by the timer IRQ!
*/
static inline void update_times(void)
{
unsigned long ticks;
ticks = jiffies - wall_jiffies;
if (ticks) {
wall_jiffies += ticks;
update_wall_time(ticks);
}
calc_load(ticks);
}
/*
* The 64-bit jiffies value is not atomic - you MUST NOT read it
* without sampling the sequence number in xtime_lock.
* jiffies is defined in the linker script...
*/
void do_timer(struct pt_regs *regs)
{
jiffies_64++;
/* prevent loading jiffies before storing new jiffies_64 value. */
barrier();
update_times();
}
#ifdef __ARCH_WANT_SYS_ALARM
/*
* For backwards compatibility? This can be done in libc so Alpha
* and all newer ports shouldn't need it.
*/
asmlinkage unsigned long sys_alarm(unsigned int seconds)
{
return alarm_setitimer(seconds);
}
#endif
#ifndef __alpha__
/*
* The Alpha uses getxpid, getxuid, and getxgid instead. Maybe this
* should be moved into arch/i386 instead?
*/
/**
* sys_getpid - return the thread group id of the current process
*
* Note, despite the name, this returns the tgid not the pid. The tgid and
* the pid are identical unless CLONE_THREAD was specified on clone() in
* which case the tgid is the same in all threads of the same group.
*
* This is SMP safe as current->tgid does not change.
*/
asmlinkage long sys_getpid(void)
{
return current->tgid;
}
/*
* Accessing ->group_leader->real_parent is not SMP-safe, it could
* change from under us. However, rather than getting any lock
* we can use an optimistic algorithm: get the parent
* pid, and go back and check that the parent is still
* the same. If it has changed (which is extremely unlikely
* indeed), we just try again..
*
* NOTE! This depends on the fact that even if we _do_
* get an old value of "parent", we can happily dereference
* the pointer (it was and remains a dereferencable kernel pointer
* no matter what): we just can't necessarily trust the result
* until we know that the parent pointer is valid.
*
* NOTE2: ->group_leader never changes from under us.
*/
asmlinkage long sys_getppid(void)
{
int pid;
struct task_struct *me = current;
struct task_struct *parent;
parent = me->group_leader->real_parent;
for (;;) {
pid = parent->tgid;
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
{
struct task_struct *old = parent;
/*
* Make sure we read the pid before re-reading the
* parent pointer:
*/
smp_rmb();
parent = me->group_leader->real_parent;
if (old != parent)
continue;
}
#endif
break;
}
return pid;
}
asmlinkage long sys_getuid(void)
{
/* Only we change this so SMP safe */
return current->uid;
}
asmlinkage long sys_geteuid(void)
{
/* Only we change this so SMP safe */
return current->euid;
}
asmlinkage long sys_getgid(void)
{
/* Only we change this so SMP safe */
return current->gid;
}
asmlinkage long sys_getegid(void)
{
/* Only we change this so SMP safe */
return current->egid;
}
#endif
static void process_timeout(unsigned long __data)
{
wake_up_process((task_t *)__data);
}
/**
* schedule_timeout - sleep until timeout
* @timeout: timeout value in jiffies
*
* Make the current task sleep until @timeout jiffies have
* elapsed. The routine will return immediately unless
* the current task state has been set (see set_current_state()).
*
* You can set the task state as follows -
*
* %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are 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
* in jiffies will be returned, or 0 if the timer expired in time
*
* The current task state is guaranteed to be TASK_RUNNING when this
* routine returns.
*
* Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
* the CPU away without a bound on the timeout. In this case the return
* value will be %MAX_SCHEDULE_TIMEOUT.
*
* In all cases the return value is guaranteed to be non-negative.
*/
fastcall signed long __sched schedule_timeout(signed long timeout)
{
struct timer_list timer;
unsigned long expire;
switch (timeout)
{
case MAX_SCHEDULE_TIMEOUT:
/*
* These two special cases are useful to be comfortable
* in the caller. Nothing more. We could take
* MAX_SCHEDULE_TIMEOUT from one of the negative value
* but I' d like to return a valid offset (>=0) to allow
* the caller to do everything it want with the retval.
*/
schedule();
goto out;
default:
/*
* Another bit of PARANOID. Note that the retval will be
* 0 since no piece of kernel is supposed to do a check
* for a negative retval of schedule_timeout() (since it
* should never happens anyway). You just have the printk()
* that will tell you if something is gone wrong and where.
*/
if (timeout < 0)
{
printk(KERN_ERR "schedule_timeout: wrong timeout "
"value %lx from %p\n", timeout,
__builtin_return_address(0));
current->state = TASK_RUNNING;
goto out;
}
}
expire = timeout + jiffies;
setup_timer(&timer, process_timeout, (unsigned long)current);
__mod_timer(&timer, expire);
schedule();
del_singleshot_timer_sync(&timer);
timeout = expire - jiffies;
out:
return timeout < 0 ? 0 : timeout;
}
EXPORT_SYMBOL(schedule_timeout);
/*
* We can use __set_current_state() here because schedule_timeout() calls
* schedule() unconditionally.
*/
signed long __sched schedule_timeout_interruptible(signed long timeout)
{
__set_current_state(TASK_INTERRUPTIBLE);
return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_interruptible);
signed long __sched schedule_timeout_uninterruptible(signed long timeout)
{
__set_current_state(TASK_UNINTERRUPTIBLE);
return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_uninterruptible);
/* Thread ID - the internal kernel "pid" */
asmlinkage long sys_gettid(void)
{
return current->pid;
}
/*
* sys_sysinfo - fill in sysinfo struct
*/
asmlinkage long sys_sysinfo(struct sysinfo __user *info)
{
struct sysinfo val;
unsigned long mem_total, sav_total;
unsigned int mem_unit, bitcount;
unsigned long seq;
memset((char *)&val, 0, sizeof(struct sysinfo));
do {
struct timespec tp;
seq = read_seqbegin(&xtime_lock);
/*
* This is annoying. The below is the same thing
* posix_get_clock_monotonic() does, but it wants to
* take the lock which we want to cover the loads stuff
* too.
*/
getnstimeofday(&tp);
tp.tv_sec += wall_to_monotonic.tv_sec;
tp.tv_nsec += wall_to_monotonic.tv_nsec;
if (tp.tv_nsec - NSEC_PER_SEC >= 0) {
tp.tv_nsec = tp.tv_nsec - NSEC_PER_SEC;
tp.tv_sec++;
}
val.uptime = tp.tv_sec + (tp.tv_nsec ? 1 : 0);
val.loads[0] = avenrun[0] << (SI_LOAD_SHIFT - FSHIFT);
val.loads[1] = avenrun[1] << (SI_LOAD_SHIFT - FSHIFT);
val.loads[2] = avenrun[2] << (SI_LOAD_SHIFT - FSHIFT);
val.procs = nr_threads;
} while (read_seqretry(&xtime_lock, seq));
si_meminfo(&val);
si_swapinfo(&val);
/*
* If the sum of all the available memory (i.e. ram + swap)
* is less than can be stored in a 32 bit unsigned long then
* we can be binary compatible with 2.2.x kernels. If not,
* well, in that case 2.2.x was broken anyways...
*
* -Erik Andersen <andersee@debian.org>
*/
mem_total = val.totalram + val.totalswap;
if (mem_total < val.totalram || mem_total < val.totalswap)
goto out;
bitcount = 0;
mem_unit = val.mem_unit;
while (mem_unit > 1) {
bitcount++;
mem_unit >>= 1;
sav_total = mem_total;
mem_total <<= 1;
if (mem_total < sav_total)
goto out;
}
/*
* If mem_total did not overflow, multiply all memory values by
* val.mem_unit and set it to 1. This leaves things compatible
* with 2.2.x, and also retains compatibility with earlier 2.4.x
* kernels...
*/
val.mem_unit = 1;
val.totalram <<= bitcount;
val.freeram <<= bitcount;
val.sharedram <<= bitcount;
val.bufferram <<= bitcount;
val.totalswap <<= bitcount;
val.freeswap <<= bitcount;
val.totalhigh <<= bitcount;
val.freehigh <<= bitcount;
out:
if (copy_to_user(info, &val, sizeof(struct sysinfo)))
return -EFAULT;
return 0;
}
static int __devinit init_timers_cpu(int cpu)
{
int j;
tvec_base_t *base;
base = per_cpu(tvec_bases, cpu);
if (!base) {
static char boot_done;
/*
* Cannot do allocation in init_timers as that runs before the
* allocator initializes (and would waste memory if there are
* more possible CPUs than will ever be installed/brought up).
*/
if (boot_done) {
base = kmalloc_node(sizeof(*base), GFP_KERNEL,
cpu_to_node(cpu));
if (!base)
return -ENOMEM;
memset(base, 0, sizeof(*base));
} else {
base = &boot_tvec_bases;
boot_done = 1;
}
per_cpu(tvec_bases, cpu) = base;
}
spin_lock_init(&base->lock);
for (j = 0; j < TVN_SIZE; j++) {
INIT_LIST_HEAD(base->tv5.vec + j);
INIT_LIST_HEAD(base->tv4.vec + j);
INIT_LIST_HEAD(base->tv3.vec + j);
INIT_LIST_HEAD(base->tv2.vec + j);
}
for (j = 0; j < TVR_SIZE; j++)
INIT_LIST_HEAD(base->tv1.vec + j);
base->timer_jiffies = jiffies;
return 0;
}
#ifdef CONFIG_HOTPLUG_CPU
static void migrate_timer_list(tvec_base_t *new_base, struct list_head *head)
{
struct timer_list *timer;
while (!list_empty(head)) {
timer = list_entry(head->next, struct timer_list, entry);
detach_timer(timer, 0);
timer->base = new_base;
internal_add_timer(new_base, timer);
}
}
static void __devinit migrate_timers(int cpu)
{
tvec_base_t *old_base;
tvec_base_t *new_base;
int i;
BUG_ON(cpu_online(cpu));
old_base = per_cpu(tvec_bases, cpu);
new_base = get_cpu_var(tvec_bases);
local_irq_disable();
spin_lock(&new_base->lock);
spin_lock(&old_base->lock);
BUG_ON(old_base->running_timer);
for (i = 0; i < TVR_SIZE; i++)
migrate_timer_list(new_base, old_base->tv1.vec + i);
for (i = 0; i < TVN_SIZE; i++) {
migrate_timer_list(new_base, old_base->tv2.vec + i);
migrate_timer_list(new_base, old_base->tv3.vec + i);
migrate_timer_list(new_base, old_base->tv4.vec + i);
migrate_timer_list(new_base, old_base->tv5.vec + i);
}
spin_unlock(&old_base->lock);
spin_unlock(&new_base->lock);
local_irq_enable();
put_cpu_var(tvec_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */
static int __devinit timer_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
long cpu = (long)hcpu;
switch(action) {
case CPU_UP_PREPARE:
if (init_timers_cpu(cpu) < 0)
return NOTIFY_BAD;
break;
#ifdef CONFIG_HOTPLUG_CPU
case CPU_DEAD:
migrate_timers(cpu);
break;
#endif
default:
break;
}
return NOTIFY_OK;
}
static struct notifier_block __devinitdata timers_nb = {
.notifier_call = timer_cpu_notify,
};
void __init init_timers(void)
{
timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
(void *)(long)smp_processor_id());
register_cpu_notifier(&timers_nb);
open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
}
#ifdef CONFIG_TIME_INTERPOLATION
struct time_interpolator *time_interpolator __read_mostly;
static struct time_interpolator *time_interpolator_list __read_mostly;
static DEFINE_SPINLOCK(time_interpolator_lock);
static inline u64 time_interpolator_get_cycles(unsigned int src)
{
unsigned long (*x)(void);
switch (src)
{
case TIME_SOURCE_FUNCTION:
x = time_interpolator->addr;
return x();
case TIME_SOURCE_MMIO64 :
return readq_relaxed((void __iomem *)time_interpolator->addr);
case TIME_SOURCE_MMIO32 :
return readl_relaxed((void __iomem *)time_interpolator->addr);
default: return get_cycles();
}
}
static inline u64 time_interpolator_get_counter(int writelock)
{
unsigned int src = time_interpolator->source;
if (time_interpolator->jitter)
{
u64 lcycle;
u64 now;
do {
lcycle = time_interpolator->last_cycle;
now = time_interpolator_get_cycles(src);
if (lcycle && time_after(lcycle, now))
return lcycle;
/* When holding the xtime write lock, there's no need
* to add the overhead of the cmpxchg. Readers are
* force to retry until the write lock is released.
*/
if (writelock) {
time_interpolator->last_cycle = now;
return now;
}
/* Keep track of the last timer value returned. The use of cmpxchg here
* will cause contention in an SMP environment.
*/
} while (unlikely(cmpxchg(&time_interpolator->last_cycle, lcycle, now) != lcycle));
return now;
}
else
return time_interpolator_get_cycles(src);
}
void time_interpolator_reset(void)
{
time_interpolator->offset = 0;
time_interpolator->last_counter = time_interpolator_get_counter(1);
}
#define GET_TI_NSECS(count,i) (((((count) - i->last_counter) & (i)->mask) * (i)->nsec_per_cyc) >> (i)->shift)
unsigned long time_interpolator_get_offset(void)
{
/* If we do not have a time interpolator set up then just return zero */
if (!time_interpolator)
return 0;
return time_interpolator->offset +
GET_TI_NSECS(time_interpolator_get_counter(0), time_interpolator);
}
#define INTERPOLATOR_ADJUST 65536
#define INTERPOLATOR_MAX_SKIP 10*INTERPOLATOR_ADJUST
static void time_interpolator_update(long delta_nsec)
{
u64 counter;
unsigned long offset;
/* If there is no time interpolator set up then do nothing */
if (!time_interpolator)
return;
/*
* The interpolator compensates for late ticks by accumulating the late
* time in time_interpolator->offset. A tick earlier than expected will
* lead to a reset of the offset and a corresponding jump of the clock
* forward. Again this only works if the interpolator clock is running
* slightly slower than the regular clock and the tuning logic insures
* that.
*/
counter = time_interpolator_get_counter(1);
offset = time_interpolator->offset +
GET_TI_NSECS(counter, time_interpolator);
if (delta_nsec < 0 || (unsigned long) delta_nsec < offset)
time_interpolator->offset = offset - delta_nsec;
else {
time_interpolator->skips++;
time_interpolator->ns_skipped += delta_nsec - offset;
time_interpolator->offset = 0;
}
time_interpolator->last_counter = counter;
/* Tuning logic for time interpolator invoked every minute or so.
* Decrease interpolator clock speed if no skips occurred and an offset is carried.
* Increase interpolator clock speed if we skip too much time.
*/
if (jiffies % INTERPOLATOR_ADJUST == 0)
{
if (time_interpolator->skips == 0 && time_interpolator->offset > TICK_NSEC)
time_interpolator->nsec_per_cyc--;
if (time_interpolator->ns_skipped > INTERPOLATOR_MAX_SKIP && time_interpolator->offset == 0)
time_interpolator->nsec_per_cyc++;
time_interpolator->skips = 0;
time_interpolator->ns_skipped = 0;
}
}
static inline int
is_better_time_interpolator(struct time_interpolator *new)
{
if (!time_interpolator)
return 1;
return new->frequency > 2*time_interpolator->frequency ||
(unsigned long)new->drift < (unsigned long)time_interpolator->drift;
}
void
register_time_interpolator(struct time_interpolator *ti)
{
unsigned long flags;
/* Sanity check */
if (ti->frequency == 0 || ti->mask == 0)
BUG();
ti->nsec_per_cyc = ((u64)NSEC_PER_SEC << ti->shift) / ti->frequency;
spin_lock(&time_interpolator_lock);
write_seqlock_irqsave(&xtime_lock, flags);
if (is_better_time_interpolator(ti)) {
time_interpolator = ti;
time_interpolator_reset();
}
write_sequnlock_irqrestore(&xtime_lock, flags);
ti->next = time_interpolator_list;
time_interpolator_list = ti;
spin_unlock(&time_interpolator_lock);
}
void
unregister_time_interpolator(struct time_interpolator *ti)
{
struct time_interpolator *curr, **prev;
unsigned long flags;
spin_lock(&time_interpolator_lock);
prev = &time_interpolator_list;
for (curr = *prev; curr; curr = curr->next) {
if (curr == ti) {
*prev = curr->next;
break;
}
prev = &curr->next;
}
write_seqlock_irqsave(&xtime_lock, flags);
if (ti == time_interpolator) {
/* we lost the best time-interpolator: */
time_interpolator = NULL;
/* find the next-best interpolator */
for (curr = time_interpolator_list; curr; curr = curr->next)
if (is_better_time_interpolator(curr))
time_interpolator = curr;
time_interpolator_reset();
}
write_sequnlock_irqrestore(&xtime_lock, flags);
spin_unlock(&time_interpolator_lock);
}
#endif /* CONFIG_TIME_INTERPOLATION */
/**
* msleep - sleep safely even with waitqueue interruptions
* @msecs: Time in milliseconds to sleep for
*/
void msleep(unsigned int msecs)
{
unsigned long timeout = msecs_to_jiffies(msecs) + 1;
while (timeout)
timeout = schedule_timeout_uninterruptible(timeout);
}
EXPORT_SYMBOL(msleep);
/**
* msleep_interruptible - sleep waiting for signals
* @msecs: Time in milliseconds to sleep for
*/
unsigned long msleep_interruptible(unsigned int msecs)
{
unsigned long timeout = msecs_to_jiffies(msecs) + 1;
while (timeout && !signal_pending(current))
timeout = schedule_timeout_interruptible(timeout);
return jiffies_to_msecs(timeout);
}
EXPORT_SYMBOL(msleep_interruptible);
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