/*
* linux/kernel/time.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* This file contains the interface functions for the various
* time related system calls: time, stime, gettimeofday, settimeofday,
* adjtime
*/
/*
* Modification history kernel/time.c
*
* 1993-09-02 Philip Gladstone
* Created file with time related functions from sched/core.c and adjtimex()
* 1993-10-08 Torsten Duwe
* adjtime interface update and CMOS clock write code
* 1995-08-13 Torsten Duwe
* kernel PLL updated to 1994-12-13 specs (rfc-1589)
* 1999-01-16 Ulrich Windl
* Introduced error checking for many cases in adjtimex().
* Updated NTP code according to technical memorandum Jan '96
* "A Kernel Model for Precision Timekeeping" by Dave Mills
* Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
* (Even though the technical memorandum forbids it)
* 2004-07-14 Christoph Lameter
* Added getnstimeofday to allow the posix timer functions to return
* with nanosecond accuracy
*/
#include <linux/jiffies.h>
#include <linux/errno.h>
#include <linux/math64.h>
#define HZ_TO_MSEC_MUL32 0xA0000000
#define HZ_TO_MSEC_ADJ32 0x0
#define HZ_TO_MSEC_SHR32 28
#define HZ_TO_MSEC_MUL64 0xA000000000000000
#define HZ_TO_MSEC_ADJ64 0x0
#define HZ_TO_MSEC_SHR64 60
#define MSEC_TO_HZ_MUL32 0xCCCCCCCD
#define MSEC_TO_HZ_ADJ32 0x733333333
#define MSEC_TO_HZ_SHR32 35
#define MSEC_TO_HZ_MUL64 0xCCCCCCCCCCCCCCCD
#define MSEC_TO_HZ_ADJ64 0x73333333333333333
#define MSEC_TO_HZ_SHR64 67
#define HZ_TO_MSEC_NUM 10
#define HZ_TO_MSEC_DEN 1
#define MSEC_TO_HZ_NUM 1
#define MSEC_TO_HZ_DEN 10
#define HZ_TO_USEC_MUL32 0x9C400000
#define HZ_TO_USEC_ADJ32 0x0
#define HZ_TO_USEC_SHR32 18
#define HZ_TO_USEC_MUL64 0x9C40000000000000
#define HZ_TO_USEC_ADJ64 0x0
#define HZ_TO_USEC_SHR64 50
#define USEC_TO_HZ_MUL32 0xD1B71759
#define USEC_TO_HZ_ADJ32 0x1FFF2E48E8A7
#define USEC_TO_HZ_SHR32 45
#define USEC_TO_HZ_MUL64 0xD1B71758E219652C
#define USEC_TO_HZ_ADJ64 0x1FFF2E48E8A71DE69AD4
#define USEC_TO_HZ_SHR64 77
#define HZ_TO_USEC_NUM 10000
#define HZ_TO_USEC_DEN 1
#define USEC_TO_HZ_NUM 1
#define USEC_TO_HZ_DEN 10000
#define MSEC_PER_SEC 1000L
#define USEC_PER_MSEC 1000L
#define NSEC_PER_USEC 1000L
#define NSEC_PER_MSEC 1000000L
#define USEC_PER_SEC 1000000L
#define NSEC_PER_SEC 1000000000L
#define FSEC_PER_SEC 1000000000000000LL
# define USER_HZ 100
/*
* Convert jiffies to milliseconds and back.
*
* Avoid unnecessary multiplications/divisions in the
* two most common HZ cases:
*/
unsigned int jiffies_to_msecs(const unsigned long j)
{
#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
return (MSEC_PER_SEC / HZ) * j;
#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
#else
# if BITS_PER_LONG == 32
return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
# else
return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
# endif
#endif
}
EXPORT_SYMBOL(jiffies_to_msecs);
unsigned int jiffies_to_usecs(const unsigned long j)
{
#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
return (USEC_PER_SEC / HZ) * j;
#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
#else
# if BITS_PER_LONG == 32
return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
# else
return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
# endif
#endif
}
EXPORT_SYMBOL(jiffies_to_usecs);
/**
* timespec_trunc - Truncate timespec to a granularity
* @t: Timespec
* @gran: Granularity in ns.
*
* Truncate a timespec to a granularity. Always rounds down. gran must
* not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns).
*/
struct timespec timespec_trunc(struct timespec t, unsigned gran)
{
/* Avoid division in the common cases 1 ns and 1 s. */
if (gran == 1) {
/* nothing */
} else if (gran == NSEC_PER_SEC) {
t.tv_nsec = 0;
} else if (gran > 1 && gran < NSEC_PER_SEC) {
t.tv_nsec -= t.tv_nsec % gran;
} else {
WARN(1, "illegal file time granularity: %u", gran);
}
return t;
}
EXPORT_SYMBOL(timespec_trunc);
/*
* mktime64 - Converts date to seconds.
* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
* Assumes input in normal date format, i.e. 1980-12-31 23:59:59
* => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
*
* [For the Julian calendar (which was used in Russia before 1917,
* Britain & colonies before 1752, anywhere else before 1582,
* and is still in use by some communities) leave out the
* -year/100+year/400 terms, and add 10.]
*
* This algorithm was first published by Gauss (I think).
*/
time64_t mktime64(const unsigned int year0, const unsigned int mon0,
const unsigned int day, const unsigned int hour,
const unsigned int min, const unsigned int sec)
{
unsigned int mon = mon0, year = year0;
/* 1..12 -> 11,12,1..10 */
if (0 >= (int) (mon -= 2)) {
mon += 12; /* Puts Feb last since it has leap day */
year -= 1;
}
return ((((time64_t)
(year/4 - year/100 + year/400 + 367*mon/12 + day) +
year*365 - 719499
)*24 + hour /* now have hours */
)*60 + min /* now have minutes */
)*60 + sec; /* finally seconds */
}
EXPORT_SYMBOL(mktime64);
/**
* set_normalized_timespec - set timespec sec and nsec parts and normalize
*
* @ts: pointer to timespec variable to be set
* @sec: seconds to set
* @nsec: nanoseconds to set
*
* Set seconds and nanoseconds field of a timespec variable and
* normalize to the timespec storage format
*
* Note: The tv_nsec part is always in the range of
* 0 <= tv_nsec < NSEC_PER_SEC
* For negative values only the tv_sec field is negative !
*/
void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
{
while (nsec >= NSEC_PER_SEC) {
/*
* The following asm() prevents the compiler from
* optimising this loop into a modulo operation. See
* also __iter_div_u64_rem() in include/linux/time.h
*/
asm("" : "+rm"(nsec));
nsec -= NSEC_PER_SEC;
++sec;
}
while (nsec < 0) {
asm("" : "+rm"(nsec));
nsec += NSEC_PER_SEC;
--sec;
}
ts->tv_sec = sec;
ts->tv_nsec = nsec;
}
EXPORT_SYMBOL(set_normalized_timespec);
/**
* ns_to_timespec - Convert nanoseconds to timespec
* @nsec: the nanoseconds value to be converted
*
* Returns the timespec representation of the nsec parameter.
*/
struct timespec ns_to_timespec(const s64 nsec)
{
struct timespec ts;
s32 rem;
if (!nsec)
return (struct timespec) {0, 0};
ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
if (unlikely(rem < 0)) {
ts.tv_sec--;
rem += NSEC_PER_SEC;
}
ts.tv_nsec = rem;
return ts;
}
EXPORT_SYMBOL(ns_to_timespec);
/**
* ns_to_timeval - Convert nanoseconds to timeval
* @nsec: the nanoseconds value to be converted
*
* Returns the timeval representation of the nsec parameter.
*/
struct timeval ns_to_timeval(const s64 nsec)
{
struct timespec ts = ns_to_timespec(nsec);
struct timeval tv;
tv.tv_sec = ts.tv_sec;
tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
return tv;
}
EXPORT_SYMBOL(ns_to_timeval);
#if BITS_PER_LONG == 32
/**
* set_normalized_timespec - set timespec sec and nsec parts and normalize
*
* @ts: pointer to timespec variable to be set
* @sec: seconds to set
* @nsec: nanoseconds to set
*
* Set seconds and nanoseconds field of a timespec variable and
* normalize to the timespec storage format
*
* Note: The tv_nsec part is always in the range of
* 0 <= tv_nsec < NSEC_PER_SEC
* For negative values only the tv_sec field is negative !
*/
void set_normalized_timespec64(struct timespec64 *ts, time64_t sec, s64 nsec)
{
while (nsec >= NSEC_PER_SEC) {
/*
* The following asm() prevents the compiler from
* optimising this loop into a modulo operation. See
* also __iter_div_u64_rem() in include/linux/time.h
*/
asm("" : "+rm"(nsec));
nsec -= NSEC_PER_SEC;
++sec;
}
while (nsec < 0) {
asm("" : "+rm"(nsec));
nsec += NSEC_PER_SEC;
--sec;
}
ts->tv_sec = sec;
ts->tv_nsec = nsec;
}
EXPORT_SYMBOL(set_normalized_timespec64);
/**
* ns_to_timespec64 - Convert nanoseconds to timespec64
* @nsec: the nanoseconds value to be converted
*
* Returns the timespec64 representation of the nsec parameter.
*/
struct timespec64 ns_to_timespec64(const s64 nsec)
{
struct timespec64 ts;
s32 rem;
if (!nsec)
return (struct timespec64) {0, 0};
ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
if (unlikely(rem < 0)) {
ts.tv_sec--;
rem += NSEC_PER_SEC;
}
ts.tv_nsec = rem;
return ts;
}
EXPORT_SYMBOL(ns_to_timespec64);
#endif
/**
* msecs_to_jiffies: - convert milliseconds to jiffies
* @m: time in milliseconds
*
* conversion is done as follows:
*
* - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
*
* - 'too large' values [that would result in larger than
* MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
*
* - all other values are converted to jiffies by either multiplying
* the input value by a factor or dividing it with a factor and
* handling any 32-bit overflows.
* for the details see __msecs_to_jiffies()
*
* msecs_to_jiffies() checks for the passed in value being a constant
* via __builtin_constant_p() allowing gcc to eliminate most of the
* code, __msecs_to_jiffies() is called if the value passed does not
* allow constant folding and the actual conversion must be done at
* runtime.
* the _msecs_to_jiffies helpers are the HZ dependent conversion
* routines found in include/linux/jiffies.h
*/
unsigned long __msecs_to_jiffies(const unsigned int m)
{
/*
* Negative value, means infinite timeout:
*/
if ((int)m < 0)
return MAX_JIFFY_OFFSET;
return _msecs_to_jiffies(m);
}
EXPORT_SYMBOL(__msecs_to_jiffies);
unsigned long __usecs_to_jiffies(const unsigned int u)
{
if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
return MAX_JIFFY_OFFSET;
return _usecs_to_jiffies(u);
}
EXPORT_SYMBOL(__usecs_to_jiffies);
/*
* The TICK_NSEC - 1 rounds up the value to the next resolution. Note
* that a remainder subtract here would not do the right thing as the
* resolution values don't fall on second boundries. I.e. the line:
* nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
* Note that due to the small error in the multiplier here, this
* rounding is incorrect for sufficiently large values of tv_nsec, but
* well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're
* OK.
*
* Rather, we just shift the bits off the right.
*
* The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
* value to a scaled second value.
*/
static unsigned long
__timespec64_to_jiffies(u64 sec, long nsec)
{
nsec = nsec + TICK_NSEC - 1;
if (sec >= MAX_SEC_IN_JIFFIES){
sec = MAX_SEC_IN_JIFFIES;
nsec = 0;
}
return ((sec * SEC_CONVERSION) +
(((u64)nsec * NSEC_CONVERSION) >>
(NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
}
static unsigned long
__timespec_to_jiffies(unsigned long sec, long nsec)
{
return __timespec64_to_jiffies((u64)sec, nsec);
}
unsigned long
timespec64_to_jiffies(const struct timespec64 *value)
{
return __timespec64_to_jiffies(value->tv_sec, value->tv_nsec);
}
EXPORT_SYMBOL(timespec64_to_jiffies);
void
jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value)
{
/*
* Convert jiffies to nanoseconds and separate with
* one divide.
*/
u32 rem;
value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
NSEC_PER_SEC, &rem);
value->tv_nsec = rem;
}
EXPORT_SYMBOL(jiffies_to_timespec64);
/*
* We could use a similar algorithm to timespec_to_jiffies (with a
* different multiplier for usec instead of nsec). But this has a
* problem with rounding: we can't exactly add TICK_NSEC - 1 to the
* usec value, since it's not necessarily integral.
*
* We could instead round in the intermediate scaled representation
* (i.e. in units of 1/2^(large scale) jiffies) but that's also
* perilous: the scaling introduces a small positive error, which
* combined with a division-rounding-upward (i.e. adding 2^(scale) - 1
* units to the intermediate before shifting) leads to accidental
* overflow and overestimates.
*
* At the cost of one additional multiplication by a constant, just
* use the timespec implementation.
*/
unsigned long
timeval_to_jiffies(const struct timeval *value)
{
return __timespec_to_jiffies(value->tv_sec,
value->tv_usec * NSEC_PER_USEC);
}
EXPORT_SYMBOL(timeval_to_jiffies);
void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
{
/*
* Convert jiffies to nanoseconds and separate with
* one divide.
*/
u32 rem;
value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
NSEC_PER_SEC, &rem);
value->tv_usec = rem / NSEC_PER_USEC;
}
EXPORT_SYMBOL(jiffies_to_timeval);
/*
* Convert jiffies/jiffies_64 to clock_t and back.
*/
clock_t jiffies_to_clock_t(unsigned long x)
{
#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
# if HZ < USER_HZ
return x * (USER_HZ / HZ);
# else
return x / (HZ / USER_HZ);
# endif
#else
return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
#endif
}
EXPORT_SYMBOL(jiffies_to_clock_t);
unsigned long clock_t_to_jiffies(unsigned long x)
{
#if (HZ % USER_HZ)==0
if (x >= ~0UL / (HZ / USER_HZ))
return ~0UL;
return x * (HZ / USER_HZ);
#else
/* Don't worry about loss of precision here .. */
if (x >= ~0UL / HZ * USER_HZ)
return ~0UL;
/* .. but do try to contain it here */
return div_u64((u64)x * HZ, USER_HZ);
#endif
}
EXPORT_SYMBOL(clock_t_to_jiffies);
u64 jiffies_64_to_clock_t(u64 x)
{
#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
# if HZ < USER_HZ
x = div_u64(x * USER_HZ, HZ);
# elif HZ > USER_HZ
x = div_u64(x, HZ / USER_HZ);
# else
/* Nothing to do */
# endif
#else
/*
* There are better ways that don't overflow early,
* but even this doesn't overflow in hundreds of years
* in 64 bits, so..
*/
x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
#endif
return x;
}
EXPORT_SYMBOL(jiffies_64_to_clock_t);
u64 nsec_to_clock_t(u64 x)
{
#if (NSEC_PER_SEC % USER_HZ) == 0
return div_u64(x, NSEC_PER_SEC / USER_HZ);
#elif (USER_HZ % 512) == 0
return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
#else
/*
* max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
* overflow after 64.99 years.
* exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
*/
return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
#endif
}
/**
* nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
*
* @n: nsecs in u64
*
* Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
* And this doesn't return MAX_JIFFY_OFFSET since this function is designed
* for scheduler, not for use in device drivers to calculate timeout value.
*
* note:
* NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
* ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
*/
u64 nsecs_to_jiffies64(u64 n)
{
#if (NSEC_PER_SEC % HZ) == 0
/* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
return div_u64(n, NSEC_PER_SEC / HZ);
#elif (HZ % 512) == 0
/* overflow after 292 years if HZ = 1024 */
return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
#else
/*
* Generic case - optimized for cases where HZ is a multiple of 3.
* overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
*/
return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
#endif
}
EXPORT_SYMBOL(nsecs_to_jiffies64);
/**
* nsecs_to_jiffies - Convert nsecs in u64 to jiffies
*
* @n: nsecs in u64
*
* Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
* And this doesn't return MAX_JIFFY_OFFSET since this function is designed
* for scheduler, not for use in device drivers to calculate timeout value.
*
* note:
* NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
* ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
*/
unsigned long nsecs_to_jiffies(u64 n)
{
return (unsigned long)nsecs_to_jiffies64(n);
}
EXPORT_SYMBOL_GPL(nsecs_to_jiffies);
/*
* Add two timespec values and do a safety check for overflow.
* It's assumed that both values are valid (>= 0)
*/
struct timespec timespec_add_safe(const struct timespec lhs,
const struct timespec rhs)
{
struct timespec res;
set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
lhs.tv_nsec + rhs.tv_nsec);
if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
res.tv_sec = TIME_T_MAX;
return res;
}