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kernel-fxtec-pro1x/kernel/timer.c
Zachary Amsden 0662b71322 [PATCH] Fix a NO_IDLE_HZ timer bug 
Under certain timing conditions, a race during boot occurs where timer
ticks are being processed on remote CPUs.  The remote timer ticks can
increment jiffies, and if this happens during a window when a timeout is
very close to expiring but a local tick has not yet been delivered, you can
end up with

1) No softirq pending
2) A local timer wheel which is not synced to jiffies
3) No high resolution timer active
4) A local timer which is supposed to fire before the current jiffies value.

In this circumstance, the comparison in next_timer_interrupt overflows,
because the base of the comparison for high resolution timers is jiffies,
but for the softirq timer wheel, it is relative the the current base of the
wheel (jiffies_base).

Signed-off-by: Zachary Amsden <zach@vmware.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-05-21 12:59:21 -07:00

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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;
tvec_base_t boot_tvec_bases;
EXPORT_SYMBOL(boot_tvec_bases);
static DEFINE_PER_CPU(tvec_base_t *, tvec_bases) = { &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);
/*
* It can happen that other CPUs service timer IRQs and increment
* jiffies, but we have not yet got a local timer tick to process
* the timer wheels. In that case, the expiry time can be before
* jiffies, but since the high-resolution timer here is relative to
* jiffies, the default expression when high-resolution timers are
* not active,
*
* time_before(MAX_JIFFY_OFFSET + jiffies, expires)
*
* would falsely evaluate to true. If that is the case, just
* return jiffies so that we can immediately fire the local timer
*/
if (time_before(expires, jiffies))
return jiffies;
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_active() * 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;
static char __devinitdata tvec_base_done[NR_CPUS];
if (!tvec_base_done[cpu]) {
static char boot_done;
if (boot_done) {
/*
* The APs use this path later in boot
*/
base = kmalloc_node(sizeof(*base), GFP_KERNEL,
cpu_to_node(cpu));
if (!base)
return -ENOMEM;
memset(base, 0, sizeof(*base));
per_cpu(tvec_bases, cpu) = base;
} else {
/*
* This is for the boot CPU - we use compile-time
* static initialisation because per-cpu memory isn't
* ready yet and because the memory allocators are not
* initialised either.
*/
boot_done = 1;
base = &boot_tvec_bases;
}
tvec_base_done[cpu] = 1;
} else {
base = per_cpu(tvec_bases, cpu);
}
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 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 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 */
BUG_ON(ti->frequency == 0 || ti->mask == 0);
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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