linux/kernel/time.c
Linus Torvalds 2008220879 Revert "sys_time() speedup"
This basically reverts commit 4e44f3497d,
while waiting for it to be re-done more completely.  There are cases of
people mixing "time()" with higher-resolution time sources, and we need
to take the nanosecond offsets into account.

Ingo has a patch that does that, but it's still under some discussion.
In the meantime, just revert back to the old simple situation of just
doing the whole exact timesource calculations.

But rather than using do_gettimeofday(), use the internal nanosecond
resolution getnstimeofday(), which at least avoids one unnecessary
conversion (since we really don't care about whether the fractional
seconds are nanoseconds or microseconds - we'll just throw them away).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-20 13:32:46 -07:00

672 lines
17 KiB
C

/*
* 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.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/module.h>
#include <linux/timex.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/syscalls.h>
#include <linux/security.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
/*
* The timezone where the local system is located. Used as a default by some
* programs who obtain this value by using gettimeofday.
*/
struct timezone sys_tz;
EXPORT_SYMBOL(sys_tz);
#ifdef __ARCH_WANT_SYS_TIME
/*
* sys_time() can be implemented in user-level using
* sys_gettimeofday(). Is this for backwards compatibility? If so,
* why not move it into the appropriate arch directory (for those
* architectures that need it).
*/
asmlinkage long sys_time(time_t __user * tloc)
{
time_t i;
struct timespec tv;
getnstimeofday(&tv);
i = tv.tv_sec;
if (tloc) {
if (put_user(i,tloc))
i = -EFAULT;
}
return i;
}
/*
* sys_stime() can be implemented in user-level using
* sys_settimeofday(). Is this for backwards compatibility? If so,
* why not move it into the appropriate arch directory (for those
* architectures that need it).
*/
asmlinkage long sys_stime(time_t __user *tptr)
{
struct timespec tv;
int err;
if (get_user(tv.tv_sec, tptr))
return -EFAULT;
tv.tv_nsec = 0;
err = security_settime(&tv, NULL);
if (err)
return err;
do_settimeofday(&tv);
return 0;
}
#endif /* __ARCH_WANT_SYS_TIME */
asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
{
if (likely(tv != NULL)) {
struct timeval ktv;
do_gettimeofday(&ktv);
if (copy_to_user(tv, &ktv, sizeof(ktv)))
return -EFAULT;
}
if (unlikely(tz != NULL)) {
if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
return -EFAULT;
}
return 0;
}
/*
* Adjust the time obtained from the CMOS to be UTC time instead of
* local time.
*
* This is ugly, but preferable to the alternatives. Otherwise we
* would either need to write a program to do it in /etc/rc (and risk
* confusion if the program gets run more than once; it would also be
* hard to make the program warp the clock precisely n hours) or
* compile in the timezone information into the kernel. Bad, bad....
*
* - TYT, 1992-01-01
*
* The best thing to do is to keep the CMOS clock in universal time (UTC)
* as real UNIX machines always do it. This avoids all headaches about
* daylight saving times and warping kernel clocks.
*/
static inline void warp_clock(void)
{
write_seqlock_irq(&xtime_lock);
wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
xtime.tv_sec += sys_tz.tz_minuteswest * 60;
write_sequnlock_irq(&xtime_lock);
clock_was_set();
}
/*
* In case for some reason the CMOS clock has not already been running
* in UTC, but in some local time: The first time we set the timezone,
* we will warp the clock so that it is ticking UTC time instead of
* local time. Presumably, if someone is setting the timezone then we
* are running in an environment where the programs understand about
* timezones. This should be done at boot time in the /etc/rc script,
* as soon as possible, so that the clock can be set right. Otherwise,
* various programs will get confused when the clock gets warped.
*/
int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
{
static int firsttime = 1;
int error = 0;
if (tv && !timespec_valid(tv))
return -EINVAL;
error = security_settime(tv, tz);
if (error)
return error;
if (tz) {
/* SMP safe, global irq locking makes it work. */
sys_tz = *tz;
if (firsttime) {
firsttime = 0;
if (!tv)
warp_clock();
}
}
if (tv)
{
/* SMP safe, again the code in arch/foo/time.c should
* globally block out interrupts when it runs.
*/
return do_settimeofday(tv);
}
return 0;
}
asmlinkage long sys_settimeofday(struct timeval __user *tv,
struct timezone __user *tz)
{
struct timeval user_tv;
struct timespec new_ts;
struct timezone new_tz;
if (tv) {
if (copy_from_user(&user_tv, tv, sizeof(*tv)))
return -EFAULT;
new_ts.tv_sec = user_tv.tv_sec;
new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
}
if (tz) {
if (copy_from_user(&new_tz, tz, sizeof(*tz)))
return -EFAULT;
}
return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
}
asmlinkage long sys_adjtimex(struct timex __user *txc_p)
{
struct timex txc; /* Local copy of parameter */
int ret;
/* Copy the user data space into the kernel copy
* structure. But bear in mind that the structures
* may change
*/
if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
return -EFAULT;
ret = do_adjtimex(&txc);
return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
}
inline struct timespec current_kernel_time(void)
{
struct timespec now;
unsigned long seq;
do {
seq = read_seqbegin(&xtime_lock);
now = xtime;
} while (read_seqretry(&xtime_lock, seq));
return now;
}
EXPORT_SYMBOL(current_kernel_time);
/**
* current_fs_time - Return FS time
* @sb: Superblock.
*
* Return the current time truncated to the time granularity supported by
* the fs.
*/
struct timespec current_fs_time(struct super_block *sb)
{
struct timespec now = current_kernel_time();
return timespec_trunc(now, sb->s_time_gran);
}
EXPORT_SYMBOL(current_fs_time);
/*
* Convert jiffies to milliseconds and back.
*
* Avoid unnecessary multiplications/divisions in the
* two most common HZ cases:
*/
unsigned int inline 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
return (j * MSEC_PER_SEC) / HZ;
#endif
}
EXPORT_SYMBOL(jiffies_to_msecs);
unsigned int inline 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
return (j * USEC_PER_SEC) / HZ;
#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. gran must be smaller than a second.
* Always rounds down.
*
* This function should be only used for timestamps returned by
* current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
* it doesn't handle the better resolution of the later.
*/
struct timespec timespec_trunc(struct timespec t, unsigned gran)
{
/*
* Division is pretty slow so avoid it for common cases.
* Currently current_kernel_time() never returns better than
* jiffies resolution. Exploit that.
*/
if (gran <= jiffies_to_usecs(1) * 1000) {
/* nothing */
} else if (gran == 1000000000) {
t.tv_nsec = 0;
} else {
t.tv_nsec -= t.tv_nsec % gran;
}
return t;
}
EXPORT_SYMBOL(timespec_trunc);
#ifndef CONFIG_GENERIC_TIME
/*
* Simulate gettimeofday using do_gettimeofday which only allows a timeval
* and therefore only yields usec accuracy
*/
void getnstimeofday(struct timespec *tv)
{
struct timeval x;
do_gettimeofday(&x);
tv->tv_sec = x.tv_sec;
tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
}
EXPORT_SYMBOL_GPL(getnstimeofday);
#endif
/* 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).
*
* WARNING: this function will overflow on 2106-02-07 06:28:16 on
* machines were long is 32-bit! (However, as time_t is signed, we
* will already get problems at other places on 2038-01-19 03:14:08)
*/
unsigned long
mktime(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 ((((unsigned long)
(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(mktime);
/**
* 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, long nsec)
{
while (nsec >= NSEC_PER_SEC) {
nsec -= NSEC_PER_SEC;
++sec;
}
while (nsec < 0) {
nsec += NSEC_PER_SEC;
--sec;
}
ts->tv_sec = sec;
ts->tv_nsec = nsec;
}
/**
* 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;
if (!nsec)
return (struct timespec) {0, 0};
ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC, &ts.tv_nsec);
if (unlikely(nsec < 0))
set_normalized_timespec(&ts, ts.tv_sec, ts.tv_nsec);
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);
/*
* When we convert to jiffies then we interpret incoming values
* the following way:
*
* - 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
*
* We must also be careful about 32-bit overflows.
*/
unsigned long msecs_to_jiffies(const unsigned int m)
{
/*
* Negative value, means infinite timeout:
*/
if ((int)m < 0)
return MAX_JIFFY_OFFSET;
#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
/*
* HZ is equal to or smaller than 1000, and 1000 is a nice
* round multiple of HZ, divide with the factor between them,
* but round upwards:
*/
return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
/*
* HZ is larger than 1000, and HZ is a nice round multiple of
* 1000 - simply multiply with the factor between them.
*
* But first make sure the multiplication result cannot
* overflow:
*/
if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
return MAX_JIFFY_OFFSET;
return m * (HZ / MSEC_PER_SEC);
#else
/*
* Generic case - multiply, round and divide. But first
* check that if we are doing a net multiplication, that
* we wouldnt overflow:
*/
if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
return MAX_JIFFY_OFFSET;
return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
#endif
}
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;
#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
return u * (HZ / USEC_PER_SEC);
#else
return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC;
#endif
}
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.
*
* 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.
*/
unsigned long
timespec_to_jiffies(const struct timespec *value)
{
unsigned long sec = value->tv_sec;
long nsec = value->tv_nsec + TICK_NSEC - 1;
if (sec >= MAX_SEC_IN_JIFFIES){
sec = MAX_SEC_IN_JIFFIES;
nsec = 0;
}
return (((u64)sec * SEC_CONVERSION) +
(((u64)nsec * NSEC_CONVERSION) >>
(NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
}
EXPORT_SYMBOL(timespec_to_jiffies);
void
jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
{
/*
* Convert jiffies to nanoseconds and separate with
* one divide.
*/
u64 nsec = (u64)jiffies * TICK_NSEC;
value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec);
}
EXPORT_SYMBOL(jiffies_to_timespec);
/* Same for "timeval"
*
* Well, almost. The problem here is that the real system resolution is
* in nanoseconds and the value being converted is in micro seconds.
* Also for some machines (those that use HZ = 1024, in-particular),
* there is a LARGE error in the tick size in microseconds.
* The solution we use is to do the rounding AFTER we convert the
* microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
* Instruction wise, this should cost only an additional add with carry
* instruction above the way it was done above.
*/
unsigned long
timeval_to_jiffies(const struct timeval *value)
{
unsigned long sec = value->tv_sec;
long usec = value->tv_usec;
if (sec >= MAX_SEC_IN_JIFFIES){
sec = MAX_SEC_IN_JIFFIES;
usec = 0;
}
return (((u64)sec * SEC_CONVERSION) +
(((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
(USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
}
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.
*/
u64 nsec = (u64)jiffies * TICK_NSEC;
long tv_usec;
value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &tv_usec);
tv_usec /= NSEC_PER_USEC;
value->tv_usec = tv_usec;
}
EXPORT_SYMBOL(jiffies_to_timeval);
/*
* Convert jiffies/jiffies_64 to clock_t and back.
*/
clock_t jiffies_to_clock_t(long x)
{
#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
return x / (HZ / USER_HZ);
#else
u64 tmp = (u64)x * TICK_NSEC;
do_div(tmp, (NSEC_PER_SEC / USER_HZ));
return (long)tmp;
#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
u64 jif;
/* Don't worry about loss of precision here .. */
if (x >= ~0UL / HZ * USER_HZ)
return ~0UL;
/* .. but do try to contain it here */
jif = x * (u64) HZ;
do_div(jif, USER_HZ);
return jif;
#endif
}
EXPORT_SYMBOL(clock_t_to_jiffies);
u64 jiffies_64_to_clock_t(u64 x)
{
#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
do_div(x, HZ / USER_HZ);
#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 *= TICK_NSEC;
do_div(x, (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
do_div(x, (NSEC_PER_SEC / USER_HZ));
#elif (USER_HZ % 512) == 0
x *= USER_HZ/512;
do_div(x, (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, ...
*/
x *= 9;
do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) /
USER_HZ));
#endif
return x;
}
#if (BITS_PER_LONG < 64)
u64 get_jiffies_64(void)
{
unsigned long seq;
u64 ret;
do {
seq = read_seqbegin(&xtime_lock);
ret = jiffies_64;
} while (read_seqretry(&xtime_lock, seq));
return ret;
}
EXPORT_SYMBOL(get_jiffies_64);
#endif
EXPORT_SYMBOL(jiffies);