linux/kernel/time/timekeeping.c
John Stultz ec145babe7 time: Fix timeekeping_get_ns overflow on 32bit systems
Daniel Lezcano reported seeing multi-second stalls from
keyboard input on his T61 laptop when NOHZ and CPU_IDLE
were enabled on a 32bit kernel.

He bisected the problem down to commit
1e75fa8be9 ("time: Condense timekeeper.xtime into xtime_sec").

After reproducing this issue, I narrowed the problem down
to the fact that timekeeping_get_ns() returns a 64bit
nsec value that hasn't been accumulated. In some cases
this value was being then stored in timespec.tv_nsec
(which is a long).

On 32bit systems, with idle times larger then 4 seconds
(or less, depending on the value of xtime_nsec), the
returned nsec value would overflow 32bits. This limited
kept time from increasing, causing timers to not expire.

The fix is to make sure we don't directly store the
result of timekeeping_get_ns() into a tv_nsec field,
instead using a 64bit nsec value which can then be
added into the timespec via timespec_add_ns().

Reported-and-bisected-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Link: http://lkml.kernel.org/r/1347405963-35715-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-13 17:39:14 +02:00

1443 lines
37 KiB
C

/*
* linux/kernel/time/timekeeping.c
*
* Kernel timekeeping code and accessor functions
*
* This code was moved from linux/kernel/timer.c.
* Please see that file for copyright and history logs.
*
*/
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/syscore_ops.h>
#include <linux/clocksource.h>
#include <linux/jiffies.h>
#include <linux/time.h>
#include <linux/tick.h>
#include <linux/stop_machine.h>
/* Structure holding internal timekeeping values. */
struct timekeeper {
/* Current clocksource used for timekeeping. */
struct clocksource *clock;
/* NTP adjusted clock multiplier */
u32 mult;
/* The shift value of the current clocksource. */
u32 shift;
/* Number of clock cycles in one NTP interval. */
cycle_t cycle_interval;
/* Number of clock shifted nano seconds in one NTP interval. */
u64 xtime_interval;
/* shifted nano seconds left over when rounding cycle_interval */
s64 xtime_remainder;
/* Raw nano seconds accumulated per NTP interval. */
u32 raw_interval;
/* Current CLOCK_REALTIME time in seconds */
u64 xtime_sec;
/* Clock shifted nano seconds */
u64 xtime_nsec;
/* Difference between accumulated time and NTP time in ntp
* shifted nano seconds. */
s64 ntp_error;
/* Shift conversion between clock shifted nano seconds and
* ntp shifted nano seconds. */
u32 ntp_error_shift;
/*
* 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.
*
* wall_to_monotonic is moved after resume from suspend for the
* monotonic time not to jump. We need to add total_sleep_time to
* wall_to_monotonic to get the real boot based time offset.
*
* - wall_to_monotonic is no longer the boot time, getboottime must be
* used instead.
*/
struct timespec wall_to_monotonic;
/* Offset clock monotonic -> clock realtime */
ktime_t offs_real;
/* time spent in suspend */
struct timespec total_sleep_time;
/* Offset clock monotonic -> clock boottime */
ktime_t offs_boot;
/* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */
struct timespec raw_time;
/* Seqlock for all timekeeper values */
seqlock_t lock;
};
static struct timekeeper timekeeper;
/*
* This read-write spinlock protects us from races in SMP while
* playing with xtime.
*/
__cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
/* flag for if timekeeping is suspended */
int __read_mostly timekeeping_suspended;
static inline void tk_normalize_xtime(struct timekeeper *tk)
{
while (tk->xtime_nsec >= ((u64)NSEC_PER_SEC << tk->shift)) {
tk->xtime_nsec -= (u64)NSEC_PER_SEC << tk->shift;
tk->xtime_sec++;
}
}
static struct timespec tk_xtime(struct timekeeper *tk)
{
struct timespec ts;
ts.tv_sec = tk->xtime_sec;
ts.tv_nsec = (long)(tk->xtime_nsec >> tk->shift);
return ts;
}
static void tk_set_xtime(struct timekeeper *tk, const struct timespec *ts)
{
tk->xtime_sec = ts->tv_sec;
tk->xtime_nsec = (u64)ts->tv_nsec << tk->shift;
}
static void tk_xtime_add(struct timekeeper *tk, const struct timespec *ts)
{
tk->xtime_sec += ts->tv_sec;
tk->xtime_nsec += (u64)ts->tv_nsec << tk->shift;
tk_normalize_xtime(tk);
}
static void tk_set_wall_to_mono(struct timekeeper *tk, struct timespec wtm)
{
struct timespec tmp;
/*
* Verify consistency of: offset_real = -wall_to_monotonic
* before modifying anything
*/
set_normalized_timespec(&tmp, -tk->wall_to_monotonic.tv_sec,
-tk->wall_to_monotonic.tv_nsec);
WARN_ON_ONCE(tk->offs_real.tv64 != timespec_to_ktime(tmp).tv64);
tk->wall_to_monotonic = wtm;
set_normalized_timespec(&tmp, -wtm.tv_sec, -wtm.tv_nsec);
tk->offs_real = timespec_to_ktime(tmp);
}
static void tk_set_sleep_time(struct timekeeper *tk, struct timespec t)
{
/* Verify consistency before modifying */
WARN_ON_ONCE(tk->offs_boot.tv64 != timespec_to_ktime(tk->total_sleep_time).tv64);
tk->total_sleep_time = t;
tk->offs_boot = timespec_to_ktime(t);
}
/**
* timekeeper_setup_internals - Set up internals to use clocksource clock.
*
* @clock: Pointer to clocksource.
*
* Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
* pair and interval request.
*
* Unless you're the timekeeping code, you should not be using this!
*/
static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
{
cycle_t interval;
u64 tmp, ntpinterval;
struct clocksource *old_clock;
old_clock = tk->clock;
tk->clock = clock;
clock->cycle_last = clock->read(clock);
/* Do the ns -> cycle conversion first, using original mult */
tmp = NTP_INTERVAL_LENGTH;
tmp <<= clock->shift;
ntpinterval = tmp;
tmp += clock->mult/2;
do_div(tmp, clock->mult);
if (tmp == 0)
tmp = 1;
interval = (cycle_t) tmp;
tk->cycle_interval = interval;
/* Go back from cycles -> shifted ns */
tk->xtime_interval = (u64) interval * clock->mult;
tk->xtime_remainder = ntpinterval - tk->xtime_interval;
tk->raw_interval =
((u64) interval * clock->mult) >> clock->shift;
/* if changing clocks, convert xtime_nsec shift units */
if (old_clock) {
int shift_change = clock->shift - old_clock->shift;
if (shift_change < 0)
tk->xtime_nsec >>= -shift_change;
else
tk->xtime_nsec <<= shift_change;
}
tk->shift = clock->shift;
tk->ntp_error = 0;
tk->ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;
/*
* The timekeeper keeps its own mult values for the currently
* active clocksource. These value will be adjusted via NTP
* to counteract clock drifting.
*/
tk->mult = clock->mult;
}
/* Timekeeper helper functions. */
static inline s64 timekeeping_get_ns(struct timekeeper *tk)
{
cycle_t cycle_now, cycle_delta;
struct clocksource *clock;
s64 nsec;
/* read clocksource: */
clock = tk->clock;
cycle_now = clock->read(clock);
/* calculate the delta since the last update_wall_time: */
cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
nsec = cycle_delta * tk->mult + tk->xtime_nsec;
nsec >>= tk->shift;
/* If arch requires, add in gettimeoffset() */
return nsec + arch_gettimeoffset();
}
static inline s64 timekeeping_get_ns_raw(struct timekeeper *tk)
{
cycle_t cycle_now, cycle_delta;
struct clocksource *clock;
s64 nsec;
/* read clocksource: */
clock = tk->clock;
cycle_now = clock->read(clock);
/* calculate the delta since the last update_wall_time: */
cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
/* convert delta to nanoseconds. */
nsec = clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift);
/* If arch requires, add in gettimeoffset() */
return nsec + arch_gettimeoffset();
}
/* must hold write on timekeeper.lock */
static void timekeeping_update(struct timekeeper *tk, bool clearntp)
{
struct timespec xt;
if (clearntp) {
tk->ntp_error = 0;
ntp_clear();
}
xt = tk_xtime(tk);
update_vsyscall(&xt, &tk->wall_to_monotonic, tk->clock, tk->mult);
}
/**
* timekeeping_forward_now - update clock to the current time
*
* Forward the current clock to update its state since the last call to
* update_wall_time(). This is useful before significant clock changes,
* as it avoids having to deal with this time offset explicitly.
*/
static void timekeeping_forward_now(struct timekeeper *tk)
{
cycle_t cycle_now, cycle_delta;
struct clocksource *clock;
s64 nsec;
clock = tk->clock;
cycle_now = clock->read(clock);
cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
clock->cycle_last = cycle_now;
tk->xtime_nsec += cycle_delta * tk->mult;
/* If arch requires, add in gettimeoffset() */
tk->xtime_nsec += (u64)arch_gettimeoffset() << tk->shift;
tk_normalize_xtime(tk);
nsec = clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift);
timespec_add_ns(&tk->raw_time, nsec);
}
/**
* getnstimeofday - Returns the time of day in a timespec
* @ts: pointer to the timespec to be set
*
* Returns the time of day in a timespec.
*/
void getnstimeofday(struct timespec *ts)
{
struct timekeeper *tk = &timekeeper;
unsigned long seq;
s64 nsecs = 0;
WARN_ON(timekeeping_suspended);
do {
seq = read_seqbegin(&tk->lock);
ts->tv_sec = tk->xtime_sec;
nsecs = timekeeping_get_ns(tk);
} while (read_seqretry(&tk->lock, seq));
ts->tv_nsec = 0;
timespec_add_ns(ts, nsecs);
}
EXPORT_SYMBOL(getnstimeofday);
ktime_t ktime_get(void)
{
struct timekeeper *tk = &timekeeper;
unsigned int seq;
s64 secs, nsecs;
WARN_ON(timekeeping_suspended);
do {
seq = read_seqbegin(&tk->lock);
secs = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
nsecs = timekeeping_get_ns(tk) + tk->wall_to_monotonic.tv_nsec;
} while (read_seqretry(&tk->lock, seq));
/*
* Use ktime_set/ktime_add_ns to create a proper ktime on
* 32-bit architectures without CONFIG_KTIME_SCALAR.
*/
return ktime_add_ns(ktime_set(secs, 0), nsecs);
}
EXPORT_SYMBOL_GPL(ktime_get);
/**
* 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 timekeeper *tk = &timekeeper;
struct timespec tomono;
s64 nsec;
unsigned int seq;
WARN_ON(timekeeping_suspended);
do {
seq = read_seqbegin(&tk->lock);
ts->tv_sec = tk->xtime_sec;
nsec = timekeeping_get_ns(tk);
tomono = tk->wall_to_monotonic;
} while (read_seqretry(&tk->lock, seq));
ts->tv_sec += tomono.tv_sec;
ts->tv_nsec = 0;
timespec_add_ns(ts, nsec + tomono.tv_nsec);
}
EXPORT_SYMBOL_GPL(ktime_get_ts);
#ifdef CONFIG_NTP_PPS
/**
* getnstime_raw_and_real - get day and raw monotonic time in timespec format
* @ts_raw: pointer to the timespec to be set to raw monotonic time
* @ts_real: pointer to the timespec to be set to the time of day
*
* This function reads both the time of day and raw monotonic time at the
* same time atomically and stores the resulting timestamps in timespec
* format.
*/
void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
{
struct timekeeper *tk = &timekeeper;
unsigned long seq;
s64 nsecs_raw, nsecs_real;
WARN_ON_ONCE(timekeeping_suspended);
do {
seq = read_seqbegin(&tk->lock);
*ts_raw = tk->raw_time;
ts_real->tv_sec = tk->xtime_sec;
ts_real->tv_nsec = 0;
nsecs_raw = timekeeping_get_ns_raw(tk);
nsecs_real = timekeeping_get_ns(tk);
} while (read_seqretry(&tk->lock, seq));
timespec_add_ns(ts_raw, nsecs_raw);
timespec_add_ns(ts_real, nsecs_real);
}
EXPORT_SYMBOL(getnstime_raw_and_real);
#endif /* CONFIG_NTP_PPS */
/**
* do_gettimeofday - Returns the time of day in a timeval
* @tv: pointer to the timeval to be set
*
* NOTE: Users should be converted to using getnstimeofday()
*/
void do_gettimeofday(struct timeval *tv)
{
struct timespec now;
getnstimeofday(&now);
tv->tv_sec = now.tv_sec;
tv->tv_usec = now.tv_nsec/1000;
}
EXPORT_SYMBOL(do_gettimeofday);
/**
* do_settimeofday - Sets the time of day
* @tv: pointer to the timespec variable containing the new time
*
* Sets the time of day to the new time and update NTP and notify hrtimers
*/
int do_settimeofday(const struct timespec *tv)
{
struct timekeeper *tk = &timekeeper;
struct timespec ts_delta, xt;
unsigned long flags;
if (!timespec_valid_strict(tv))
return -EINVAL;
write_seqlock_irqsave(&tk->lock, flags);
timekeeping_forward_now(tk);
xt = tk_xtime(tk);
ts_delta.tv_sec = tv->tv_sec - xt.tv_sec;
ts_delta.tv_nsec = tv->tv_nsec - xt.tv_nsec;
tk_set_wall_to_mono(tk, timespec_sub(tk->wall_to_monotonic, ts_delta));
tk_set_xtime(tk, tv);
timekeeping_update(tk, true);
write_sequnlock_irqrestore(&tk->lock, flags);
/* signal hrtimers about time change */
clock_was_set();
return 0;
}
EXPORT_SYMBOL(do_settimeofday);
/**
* timekeeping_inject_offset - Adds or subtracts from the current time.
* @tv: pointer to the timespec variable containing the offset
*
* Adds or subtracts an offset value from the current time.
*/
int timekeeping_inject_offset(struct timespec *ts)
{
struct timekeeper *tk = &timekeeper;
unsigned long flags;
struct timespec tmp;
int ret = 0;
if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;
write_seqlock_irqsave(&tk->lock, flags);
timekeeping_forward_now(tk);
/* Make sure the proposed value is valid */
tmp = timespec_add(tk_xtime(tk), *ts);
if (!timespec_valid_strict(&tmp)) {
ret = -EINVAL;
goto error;
}
tk_xtime_add(tk, ts);
tk_set_wall_to_mono(tk, timespec_sub(tk->wall_to_monotonic, *ts));
error: /* even if we error out, we forwarded the time, so call update */
timekeeping_update(tk, true);
write_sequnlock_irqrestore(&tk->lock, flags);
/* signal hrtimers about time change */
clock_was_set();
return ret;
}
EXPORT_SYMBOL(timekeeping_inject_offset);
/**
* change_clocksource - Swaps clocksources if a new one is available
*
* Accumulates current time interval and initializes new clocksource
*/
static int change_clocksource(void *data)
{
struct timekeeper *tk = &timekeeper;
struct clocksource *new, *old;
unsigned long flags;
new = (struct clocksource *) data;
write_seqlock_irqsave(&tk->lock, flags);
timekeeping_forward_now(tk);
if (!new->enable || new->enable(new) == 0) {
old = tk->clock;
tk_setup_internals(tk, new);
if (old->disable)
old->disable(old);
}
timekeeping_update(tk, true);
write_sequnlock_irqrestore(&tk->lock, flags);
return 0;
}
/**
* timekeeping_notify - Install a new clock source
* @clock: pointer to the clock source
*
* This function is called from clocksource.c after a new, better clock
* source has been registered. The caller holds the clocksource_mutex.
*/
void timekeeping_notify(struct clocksource *clock)
{
struct timekeeper *tk = &timekeeper;
if (tk->clock == clock)
return;
stop_machine(change_clocksource, clock, NULL);
tick_clock_notify();
}
/**
* ktime_get_real - get the real (wall-) time in ktime_t format
*
* returns the time in ktime_t format
*/
ktime_t ktime_get_real(void)
{
struct timespec now;
getnstimeofday(&now);
return timespec_to_ktime(now);
}
EXPORT_SYMBOL_GPL(ktime_get_real);
/**
* getrawmonotonic - Returns the raw monotonic time in a timespec
* @ts: pointer to the timespec to be set
*
* Returns the raw monotonic time (completely un-modified by ntp)
*/
void getrawmonotonic(struct timespec *ts)
{
struct timekeeper *tk = &timekeeper;
unsigned long seq;
s64 nsecs;
do {
seq = read_seqbegin(&tk->lock);
nsecs = timekeeping_get_ns_raw(tk);
*ts = tk->raw_time;
} while (read_seqretry(&tk->lock, seq));
timespec_add_ns(ts, nsecs);
}
EXPORT_SYMBOL(getrawmonotonic);
/**
* timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
*/
int timekeeping_valid_for_hres(void)
{
struct timekeeper *tk = &timekeeper;
unsigned long seq;
int ret;
do {
seq = read_seqbegin(&tk->lock);
ret = tk->clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
} while (read_seqretry(&tk->lock, seq));
return ret;
}
/**
* timekeeping_max_deferment - Returns max time the clocksource can be deferred
*/
u64 timekeeping_max_deferment(void)
{
struct timekeeper *tk = &timekeeper;
unsigned long seq;
u64 ret;
do {
seq = read_seqbegin(&tk->lock);
ret = tk->clock->max_idle_ns;
} while (read_seqretry(&tk->lock, seq));
return ret;
}
/**
* read_persistent_clock - Return time from the persistent clock.
*
* Weak dummy function for arches that do not yet support it.
* Reads the time from the battery backed persistent clock.
* Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
*
* XXX - Do be sure to remove it once all arches implement it.
*/
void __attribute__((weak)) read_persistent_clock(struct timespec *ts)
{
ts->tv_sec = 0;
ts->tv_nsec = 0;
}
/**
* read_boot_clock - Return time of the system start.
*
* Weak dummy function for arches that do not yet support it.
* Function to read the exact time the system has been started.
* Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
*
* XXX - Do be sure to remove it once all arches implement it.
*/
void __attribute__((weak)) read_boot_clock(struct timespec *ts)
{
ts->tv_sec = 0;
ts->tv_nsec = 0;
}
/*
* timekeeping_init - Initializes the clocksource and common timekeeping values
*/
void __init timekeeping_init(void)
{
struct timekeeper *tk = &timekeeper;
struct clocksource *clock;
unsigned long flags;
struct timespec now, boot, tmp;
read_persistent_clock(&now);
if (!timespec_valid_strict(&now)) {
pr_warn("WARNING: Persistent clock returned invalid value!\n"
" Check your CMOS/BIOS settings.\n");
now.tv_sec = 0;
now.tv_nsec = 0;
}
read_boot_clock(&boot);
if (!timespec_valid_strict(&boot)) {
pr_warn("WARNING: Boot clock returned invalid value!\n"
" Check your CMOS/BIOS settings.\n");
boot.tv_sec = 0;
boot.tv_nsec = 0;
}
seqlock_init(&tk->lock);
ntp_init();
write_seqlock_irqsave(&tk->lock, flags);
clock = clocksource_default_clock();
if (clock->enable)
clock->enable(clock);
tk_setup_internals(tk, clock);
tk_set_xtime(tk, &now);
tk->raw_time.tv_sec = 0;
tk->raw_time.tv_nsec = 0;
if (boot.tv_sec == 0 && boot.tv_nsec == 0)
boot = tk_xtime(tk);
set_normalized_timespec(&tmp, -boot.tv_sec, -boot.tv_nsec);
tk_set_wall_to_mono(tk, tmp);
tmp.tv_sec = 0;
tmp.tv_nsec = 0;
tk_set_sleep_time(tk, tmp);
write_sequnlock_irqrestore(&tk->lock, flags);
}
/* time in seconds when suspend began */
static struct timespec timekeeping_suspend_time;
/**
* __timekeeping_inject_sleeptime - Internal function to add sleep interval
* @delta: pointer to a timespec delta value
*
* Takes a timespec offset measuring a suspend interval and properly
* adds the sleep offset to the timekeeping variables.
*/
static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
struct timespec *delta)
{
if (!timespec_valid_strict(delta)) {
printk(KERN_WARNING "__timekeeping_inject_sleeptime: Invalid "
"sleep delta value!\n");
return;
}
tk_xtime_add(tk, delta);
tk_set_wall_to_mono(tk, timespec_sub(tk->wall_to_monotonic, *delta));
tk_set_sleep_time(tk, timespec_add(tk->total_sleep_time, *delta));
}
/**
* timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
* @delta: pointer to a timespec delta value
*
* This hook is for architectures that cannot support read_persistent_clock
* because their RTC/persistent clock is only accessible when irqs are enabled.
*
* This function should only be called by rtc_resume(), and allows
* a suspend offset to be injected into the timekeeping values.
*/
void timekeeping_inject_sleeptime(struct timespec *delta)
{
struct timekeeper *tk = &timekeeper;
unsigned long flags;
struct timespec ts;
/* Make sure we don't set the clock twice */
read_persistent_clock(&ts);
if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
return;
write_seqlock_irqsave(&tk->lock, flags);
timekeeping_forward_now(tk);
__timekeeping_inject_sleeptime(tk, delta);
timekeeping_update(tk, true);
write_sequnlock_irqrestore(&tk->lock, flags);
/* signal hrtimers about time change */
clock_was_set();
}
/**
* timekeeping_resume - Resumes the generic timekeeping subsystem.
*
* This is for the generic clocksource timekeeping.
* xtime/wall_to_monotonic/jiffies/etc are
* still managed by arch specific suspend/resume code.
*/
static void timekeeping_resume(void)
{
struct timekeeper *tk = &timekeeper;
unsigned long flags;
struct timespec ts;
read_persistent_clock(&ts);
clocksource_resume();
write_seqlock_irqsave(&tk->lock, flags);
if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
ts = timespec_sub(ts, timekeeping_suspend_time);
__timekeeping_inject_sleeptime(tk, &ts);
}
/* re-base the last cycle value */
tk->clock->cycle_last = tk->clock->read(tk->clock);
tk->ntp_error = 0;
timekeeping_suspended = 0;
timekeeping_update(tk, false);
write_sequnlock_irqrestore(&tk->lock, flags);
touch_softlockup_watchdog();
clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
/* Resume hrtimers */
hrtimers_resume();
}
static int timekeeping_suspend(void)
{
struct timekeeper *tk = &timekeeper;
unsigned long flags;
struct timespec delta, delta_delta;
static struct timespec old_delta;
read_persistent_clock(&timekeeping_suspend_time);
write_seqlock_irqsave(&tk->lock, flags);
timekeeping_forward_now(tk);
timekeeping_suspended = 1;
/*
* To avoid drift caused by repeated suspend/resumes,
* which each can add ~1 second drift error,
* try to compensate so the difference in system time
* and persistent_clock time stays close to constant.
*/
delta = timespec_sub(tk_xtime(tk), timekeeping_suspend_time);
delta_delta = timespec_sub(delta, old_delta);
if (abs(delta_delta.tv_sec) >= 2) {
/*
* if delta_delta is too large, assume time correction
* has occured and set old_delta to the current delta.
*/
old_delta = delta;
} else {
/* Otherwise try to adjust old_system to compensate */
timekeeping_suspend_time =
timespec_add(timekeeping_suspend_time, delta_delta);
}
write_sequnlock_irqrestore(&tk->lock, flags);
clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
clocksource_suspend();
return 0;
}
/* sysfs resume/suspend bits for timekeeping */
static struct syscore_ops timekeeping_syscore_ops = {
.resume = timekeeping_resume,
.suspend = timekeeping_suspend,
};
static int __init timekeeping_init_ops(void)
{
register_syscore_ops(&timekeeping_syscore_ops);
return 0;
}
device_initcall(timekeeping_init_ops);
/*
* If the error is already larger, we look ahead even further
* to compensate for late or lost adjustments.
*/
static __always_inline int timekeeping_bigadjust(struct timekeeper *tk,
s64 error, s64 *interval,
s64 *offset)
{
s64 tick_error, i;
u32 look_ahead, adj;
s32 error2, mult;
/*
* Use the current error value to determine how much to look ahead.
* The larger the error the slower we adjust for it to avoid problems
* with losing too many ticks, otherwise we would overadjust and
* produce an even larger error. The smaller the adjustment the
* faster we try to adjust for it, as lost ticks can do less harm
* here. This is tuned so that an error of about 1 msec is adjusted
* within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
*/
error2 = tk->ntp_error >> (NTP_SCALE_SHIFT + 22 - 2 * SHIFT_HZ);
error2 = abs(error2);
for (look_ahead = 0; error2 > 0; look_ahead++)
error2 >>= 2;
/*
* Now calculate the error in (1 << look_ahead) ticks, but first
* remove the single look ahead already included in the error.
*/
tick_error = ntp_tick_length() >> (tk->ntp_error_shift + 1);
tick_error -= tk->xtime_interval >> 1;
error = ((error - tick_error) >> look_ahead) + tick_error;
/* Finally calculate the adjustment shift value. */
i = *interval;
mult = 1;
if (error < 0) {
error = -error;
*interval = -*interval;
*offset = -*offset;
mult = -1;
}
for (adj = 0; error > i; adj++)
error >>= 1;
*interval <<= adj;
*offset <<= adj;
return mult << adj;
}
/*
* Adjust the multiplier to reduce the error value,
* this is optimized for the most common adjustments of -1,0,1,
* for other values we can do a bit more work.
*/
static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
{
s64 error, interval = tk->cycle_interval;
int adj;
/*
* The point of this is to check if the error is greater than half
* an interval.
*
* First we shift it down from NTP_SHIFT to clocksource->shifted nsecs.
*
* Note we subtract one in the shift, so that error is really error*2.
* This "saves" dividing(shifting) interval twice, but keeps the
* (error > interval) comparison as still measuring if error is
* larger than half an interval.
*
* Note: It does not "save" on aggravation when reading the code.
*/
error = tk->ntp_error >> (tk->ntp_error_shift - 1);
if (error > interval) {
/*
* We now divide error by 4(via shift), which checks if
* the error is greater than twice the interval.
* If it is greater, we need a bigadjust, if its smaller,
* we can adjust by 1.
*/
error >>= 2;
/*
* XXX - In update_wall_time, we round up to the next
* nanosecond, and store the amount rounded up into
* the error. This causes the likely below to be unlikely.
*
* The proper fix is to avoid rounding up by using
* the high precision tk->xtime_nsec instead of
* xtime.tv_nsec everywhere. Fixing this will take some
* time.
*/
if (likely(error <= interval))
adj = 1;
else
adj = timekeeping_bigadjust(tk, error, &interval, &offset);
} else {
if (error < -interval) {
/* See comment above, this is just switched for the negative */
error >>= 2;
if (likely(error >= -interval)) {
adj = -1;
interval = -interval;
offset = -offset;
} else {
adj = timekeeping_bigadjust(tk, error, &interval, &offset);
}
} else {
goto out_adjust;
}
}
if (unlikely(tk->clock->maxadj &&
(tk->mult + adj > tk->clock->mult + tk->clock->maxadj))) {
printk_once(KERN_WARNING
"Adjusting %s more than 11%% (%ld vs %ld)\n",
tk->clock->name, (long)tk->mult + adj,
(long)tk->clock->mult + tk->clock->maxadj);
}
/*
* So the following can be confusing.
*
* To keep things simple, lets assume adj == 1 for now.
*
* When adj != 1, remember that the interval and offset values
* have been appropriately scaled so the math is the same.
*
* The basic idea here is that we're increasing the multiplier
* by one, this causes the xtime_interval to be incremented by
* one cycle_interval. This is because:
* xtime_interval = cycle_interval * mult
* So if mult is being incremented by one:
* xtime_interval = cycle_interval * (mult + 1)
* Its the same as:
* xtime_interval = (cycle_interval * mult) + cycle_interval
* Which can be shortened to:
* xtime_interval += cycle_interval
*
* So offset stores the non-accumulated cycles. Thus the current
* time (in shifted nanoseconds) is:
* now = (offset * adj) + xtime_nsec
* Now, even though we're adjusting the clock frequency, we have
* to keep time consistent. In other words, we can't jump back
* in time, and we also want to avoid jumping forward in time.
*
* So given the same offset value, we need the time to be the same
* both before and after the freq adjustment.
* now = (offset * adj_1) + xtime_nsec_1
* now = (offset * adj_2) + xtime_nsec_2
* So:
* (offset * adj_1) + xtime_nsec_1 =
* (offset * adj_2) + xtime_nsec_2
* And we know:
* adj_2 = adj_1 + 1
* So:
* (offset * adj_1) + xtime_nsec_1 =
* (offset * (adj_1+1)) + xtime_nsec_2
* (offset * adj_1) + xtime_nsec_1 =
* (offset * adj_1) + offset + xtime_nsec_2
* Canceling the sides:
* xtime_nsec_1 = offset + xtime_nsec_2
* Which gives us:
* xtime_nsec_2 = xtime_nsec_1 - offset
* Which simplfies to:
* xtime_nsec -= offset
*
* XXX - TODO: Doc ntp_error calculation.
*/
tk->mult += adj;
tk->xtime_interval += interval;
tk->xtime_nsec -= offset;
tk->ntp_error -= (interval - offset) << tk->ntp_error_shift;
out_adjust:
/*
* It may be possible that when we entered this function, xtime_nsec
* was very small. Further, if we're slightly speeding the clocksource
* in the code above, its possible the required corrective factor to
* xtime_nsec could cause it to underflow.
*
* Now, since we already accumulated the second, cannot simply roll
* the accumulated second back, since the NTP subsystem has been
* notified via second_overflow. So instead we push xtime_nsec forward
* by the amount we underflowed, and add that amount into the error.
*
* We'll correct this error next time through this function, when
* xtime_nsec is not as small.
*/
if (unlikely((s64)tk->xtime_nsec < 0)) {
s64 neg = -(s64)tk->xtime_nsec;
tk->xtime_nsec = 0;
tk->ntp_error += neg << tk->ntp_error_shift;
}
}
/**
* accumulate_nsecs_to_secs - Accumulates nsecs into secs
*
* Helper function that accumulates a the nsecs greater then a second
* from the xtime_nsec field to the xtime_secs field.
* It also calls into the NTP code to handle leapsecond processing.
*
*/
static inline void accumulate_nsecs_to_secs(struct timekeeper *tk)
{
u64 nsecps = (u64)NSEC_PER_SEC << tk->shift;
while (tk->xtime_nsec >= nsecps) {
int leap;
tk->xtime_nsec -= nsecps;
tk->xtime_sec++;
/* Figure out if its a leap sec and apply if needed */
leap = second_overflow(tk->xtime_sec);
if (unlikely(leap)) {
struct timespec ts;
tk->xtime_sec += leap;
ts.tv_sec = leap;
ts.tv_nsec = 0;
tk_set_wall_to_mono(tk,
timespec_sub(tk->wall_to_monotonic, ts));
clock_was_set_delayed();
}
}
}
/**
* logarithmic_accumulation - shifted accumulation of cycles
*
* This functions accumulates a shifted interval of cycles into
* into a shifted interval nanoseconds. Allows for O(log) accumulation
* loop.
*
* Returns the unconsumed cycles.
*/
static cycle_t logarithmic_accumulation(struct timekeeper *tk, cycle_t offset,
u32 shift)
{
u64 raw_nsecs;
/* If the offset is smaller then a shifted interval, do nothing */
if (offset < tk->cycle_interval<<shift)
return offset;
/* Accumulate one shifted interval */
offset -= tk->cycle_interval << shift;
tk->clock->cycle_last += tk->cycle_interval << shift;
tk->xtime_nsec += tk->xtime_interval << shift;
accumulate_nsecs_to_secs(tk);
/* Accumulate raw time */
raw_nsecs = tk->raw_interval << shift;
raw_nsecs += tk->raw_time.tv_nsec;
if (raw_nsecs >= NSEC_PER_SEC) {
u64 raw_secs = raw_nsecs;
raw_nsecs = do_div(raw_secs, NSEC_PER_SEC);
tk->raw_time.tv_sec += raw_secs;
}
tk->raw_time.tv_nsec = raw_nsecs;
/* Accumulate error between NTP and clock interval */
tk->ntp_error += ntp_tick_length() << shift;
tk->ntp_error -= (tk->xtime_interval + tk->xtime_remainder) <<
(tk->ntp_error_shift + shift);
return offset;
}
/**
* update_wall_time - Uses the current clocksource to increment the wall time
*
*/
static void update_wall_time(void)
{
struct clocksource *clock;
struct timekeeper *tk = &timekeeper;
cycle_t offset;
int shift = 0, maxshift;
unsigned long flags;
s64 remainder;
write_seqlock_irqsave(&tk->lock, flags);
/* Make sure we're fully resumed: */
if (unlikely(timekeeping_suspended))
goto out;
clock = tk->clock;
#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
offset = tk->cycle_interval;
#else
offset = (clock->read(clock) - clock->cycle_last) & clock->mask;
#endif
/* Check if there's really nothing to do */
if (offset < tk->cycle_interval)
goto out;
/*
* With NO_HZ we may have to accumulate many cycle_intervals
* (think "ticks") worth of time at once. To do this efficiently,
* we calculate the largest doubling multiple of cycle_intervals
* that is smaller than the offset. We then accumulate that
* chunk in one go, and then try to consume the next smaller
* doubled multiple.
*/
shift = ilog2(offset) - ilog2(tk->cycle_interval);
shift = max(0, shift);
/* Bound shift to one less than what overflows tick_length */
maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1;
shift = min(shift, maxshift);
while (offset >= tk->cycle_interval) {
offset = logarithmic_accumulation(tk, offset, shift);
if (offset < tk->cycle_interval<<shift)
shift--;
}
/* correct the clock when NTP error is too big */
timekeeping_adjust(tk, offset);
/*
* Store only full nanoseconds into xtime_nsec after rounding
* it up and add the remainder to the error difference.
* XXX - This is necessary to avoid small 1ns inconsistnecies caused
* by truncating the remainder in vsyscalls. However, it causes
* additional work to be done in timekeeping_adjust(). Once
* the vsyscall implementations are converted to use xtime_nsec
* (shifted nanoseconds), this can be killed.
*/
remainder = tk->xtime_nsec & ((1ULL << tk->shift) - 1);
tk->xtime_nsec -= remainder;
tk->xtime_nsec += 1ULL << tk->shift;
tk->ntp_error += remainder << tk->ntp_error_shift;
/*
* Finally, make sure that after the rounding
* xtime_nsec isn't larger than NSEC_PER_SEC
*/
accumulate_nsecs_to_secs(tk);
timekeeping_update(tk, false);
out:
write_sequnlock_irqrestore(&tk->lock, flags);
}
/**
* getboottime - Return the real time of system boot.
* @ts: pointer to the timespec to be set
*
* Returns the wall-time of boot in a timespec.
*
* This is based on the wall_to_monotonic offset and the total suspend
* time. Calls to settimeofday will affect the value returned (which
* basically means that however wrong your real time clock is at boot time,
* you get the right time here).
*/
void getboottime(struct timespec *ts)
{
struct timekeeper *tk = &timekeeper;
struct timespec boottime = {
.tv_sec = tk->wall_to_monotonic.tv_sec +
tk->total_sleep_time.tv_sec,
.tv_nsec = tk->wall_to_monotonic.tv_nsec +
tk->total_sleep_time.tv_nsec
};
set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec);
}
EXPORT_SYMBOL_GPL(getboottime);
/**
* get_monotonic_boottime - Returns monotonic time since boot
* @ts: pointer to the timespec to be set
*
* Returns the monotonic time since boot in a timespec.
*
* This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
* includes the time spent in suspend.
*/
void get_monotonic_boottime(struct timespec *ts)
{
struct timekeeper *tk = &timekeeper;
struct timespec tomono, sleep;
s64 nsec;
unsigned int seq;
WARN_ON(timekeeping_suspended);
do {
seq = read_seqbegin(&tk->lock);
ts->tv_sec = tk->xtime_sec;
nsec = timekeeping_get_ns(tk);
tomono = tk->wall_to_monotonic;
sleep = tk->total_sleep_time;
} while (read_seqretry(&tk->lock, seq));
ts->tv_sec += tomono.tv_sec + sleep.tv_sec;
ts->tv_nsec = 0;
timespec_add_ns(ts, nsec + tomono.tv_nsec + sleep.tv_nsec);
}
EXPORT_SYMBOL_GPL(get_monotonic_boottime);
/**
* ktime_get_boottime - Returns monotonic time since boot in a ktime
*
* Returns the monotonic time since boot in a ktime
*
* This is similar to CLOCK_MONTONIC/ktime_get, but also
* includes the time spent in suspend.
*/
ktime_t ktime_get_boottime(void)
{
struct timespec ts;
get_monotonic_boottime(&ts);
return timespec_to_ktime(ts);
}
EXPORT_SYMBOL_GPL(ktime_get_boottime);
/**
* monotonic_to_bootbased - Convert the monotonic time to boot based.
* @ts: pointer to the timespec to be converted
*/
void monotonic_to_bootbased(struct timespec *ts)
{
struct timekeeper *tk = &timekeeper;
*ts = timespec_add(*ts, tk->total_sleep_time);
}
EXPORT_SYMBOL_GPL(monotonic_to_bootbased);
unsigned long get_seconds(void)
{
struct timekeeper *tk = &timekeeper;
return tk->xtime_sec;
}
EXPORT_SYMBOL(get_seconds);
struct timespec __current_kernel_time(void)
{
struct timekeeper *tk = &timekeeper;
return tk_xtime(tk);
}
struct timespec current_kernel_time(void)
{
struct timekeeper *tk = &timekeeper;
struct timespec now;
unsigned long seq;
do {
seq = read_seqbegin(&tk->lock);
now = tk_xtime(tk);
} while (read_seqretry(&tk->lock, seq));
return now;
}
EXPORT_SYMBOL(current_kernel_time);
struct timespec get_monotonic_coarse(void)
{
struct timekeeper *tk = &timekeeper;
struct timespec now, mono;
unsigned long seq;
do {
seq = read_seqbegin(&tk->lock);
now = tk_xtime(tk);
mono = tk->wall_to_monotonic;
} while (read_seqretry(&tk->lock, seq));
set_normalized_timespec(&now, now.tv_sec + mono.tv_sec,
now.tv_nsec + mono.tv_nsec);
return now;
}
/*
* 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(unsigned long ticks)
{
jiffies_64 += ticks;
update_wall_time();
calc_global_load(ticks);
}
/**
* get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic,
* and sleep offsets.
* @xtim: pointer to timespec to be set with xtime
* @wtom: pointer to timespec to be set with wall_to_monotonic
* @sleep: pointer to timespec to be set with time in suspend
*/
void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
struct timespec *wtom, struct timespec *sleep)
{
struct timekeeper *tk = &timekeeper;
unsigned long seq;
do {
seq = read_seqbegin(&tk->lock);
*xtim = tk_xtime(tk);
*wtom = tk->wall_to_monotonic;
*sleep = tk->total_sleep_time;
} while (read_seqretry(&tk->lock, seq));
}
#ifdef CONFIG_HIGH_RES_TIMERS
/**
* ktime_get_update_offsets - hrtimer helper
* @offs_real: pointer to storage for monotonic -> realtime offset
* @offs_boot: pointer to storage for monotonic -> boottime offset
*
* Returns current monotonic time and updates the offsets
* Called from hrtimer_interupt() or retrigger_next_event()
*/
ktime_t ktime_get_update_offsets(ktime_t *offs_real, ktime_t *offs_boot)
{
struct timekeeper *tk = &timekeeper;
ktime_t now;
unsigned int seq;
u64 secs, nsecs;
do {
seq = read_seqbegin(&tk->lock);
secs = tk->xtime_sec;
nsecs = timekeeping_get_ns(tk);
*offs_real = tk->offs_real;
*offs_boot = tk->offs_boot;
} while (read_seqretry(&tk->lock, seq));
now = ktime_add_ns(ktime_set(secs, 0), nsecs);
now = ktime_sub(now, *offs_real);
return now;
}
#endif
/**
* ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
*/
ktime_t ktime_get_monotonic_offset(void)
{
struct timekeeper *tk = &timekeeper;
unsigned long seq;
struct timespec wtom;
do {
seq = read_seqbegin(&tk->lock);
wtom = tk->wall_to_monotonic;
} while (read_seqretry(&tk->lock, seq));
return timespec_to_ktime(wtom);
}
EXPORT_SYMBOL_GPL(ktime_get_monotonic_offset);
/**
* xtime_update() - advances the timekeeping infrastructure
* @ticks: number of ticks, that have elapsed since the last call.
*
* Must be called with interrupts disabled.
*/
void xtime_update(unsigned long ticks)
{
write_seqlock(&xtime_lock);
do_timer(ticks);
write_sequnlock(&xtime_lock);
}