Merge branch 'master' of /pub/scm/linux/kernel/git/torvalds/linux-2.6
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / time.c
blobba9b338d1835e071273d8f8f8d2a054ab9c95790
1 /*
2 * linux/kernel/time.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * This file contains the interface functions for the various
7 * time related system calls: time, stime, gettimeofday, settimeofday,
8 * adjtime
9 */
11 * Modification history kernel/time.c
13 * 1993-09-02 Philip Gladstone
14 * Created file with time related functions from sched.c and adjtimex()
15 * 1993-10-08 Torsten Duwe
16 * adjtime interface update and CMOS clock write code
17 * 1995-08-13 Torsten Duwe
18 * kernel PLL updated to 1994-12-13 specs (rfc-1589)
19 * 1999-01-16 Ulrich Windl
20 * Introduced error checking for many cases in adjtimex().
21 * Updated NTP code according to technical memorandum Jan '96
22 * "A Kernel Model for Precision Timekeeping" by Dave Mills
23 * Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
24 * (Even though the technical memorandum forbids it)
25 * 2004-07-14 Christoph Lameter
26 * Added getnstimeofday to allow the posix timer functions to return
27 * with nanosecond accuracy
30 #include <linux/module.h>
31 #include <linux/timex.h>
32 #include <linux/capability.h>
33 #include <linux/clocksource.h>
34 #include <linux/errno.h>
35 #include <linux/syscalls.h>
36 #include <linux/security.h>
37 #include <linux/fs.h>
38 #include <linux/math64.h>
39 #include <linux/ptrace.h>
41 #include <asm/uaccess.h>
42 #include <asm/unistd.h>
44 #include "timeconst.h"
47 * The timezone where the local system is located. Used as a default by some
48 * programs who obtain this value by using gettimeofday.
50 struct timezone sys_tz;
52 EXPORT_SYMBOL(sys_tz);
54 #ifdef __ARCH_WANT_SYS_TIME
57 * sys_time() can be implemented in user-level using
58 * sys_gettimeofday(). Is this for backwards compatibility? If so,
59 * why not move it into the appropriate arch directory (for those
60 * architectures that need it).
62 SYSCALL_DEFINE1(time, time_t __user *, tloc)
64 time_t i = get_seconds();
66 if (tloc) {
67 if (put_user(i,tloc))
68 return -EFAULT;
70 force_successful_syscall_return();
71 return i;
75 * sys_stime() can be implemented in user-level using
76 * sys_settimeofday(). Is this for backwards compatibility? If so,
77 * why not move it into the appropriate arch directory (for those
78 * architectures that need it).
81 SYSCALL_DEFINE1(stime, time_t __user *, tptr)
83 struct timespec tv;
84 int err;
86 if (get_user(tv.tv_sec, tptr))
87 return -EFAULT;
89 tv.tv_nsec = 0;
91 err = security_settime(&tv, NULL);
92 if (err)
93 return err;
95 do_settimeofday(&tv);
96 return 0;
99 #endif /* __ARCH_WANT_SYS_TIME */
101 SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv,
102 struct timezone __user *, tz)
104 if (likely(tv != NULL)) {
105 struct timeval ktv;
106 do_gettimeofday(&ktv);
107 if (copy_to_user(tv, &ktv, sizeof(ktv)))
108 return -EFAULT;
110 if (unlikely(tz != NULL)) {
111 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
112 return -EFAULT;
114 return 0;
118 * Adjust the time obtained from the CMOS to be UTC time instead of
119 * local time.
121 * This is ugly, but preferable to the alternatives. Otherwise we
122 * would either need to write a program to do it in /etc/rc (and risk
123 * confusion if the program gets run more than once; it would also be
124 * hard to make the program warp the clock precisely n hours) or
125 * compile in the timezone information into the kernel. Bad, bad....
127 * - TYT, 1992-01-01
129 * The best thing to do is to keep the CMOS clock in universal time (UTC)
130 * as real UNIX machines always do it. This avoids all headaches about
131 * daylight saving times and warping kernel clocks.
133 static inline void warp_clock(void)
135 struct timespec adjust;
137 adjust = current_kernel_time();
138 adjust.tv_sec += sys_tz.tz_minuteswest * 60;
139 do_settimeofday(&adjust);
143 * In case for some reason the CMOS clock has not already been running
144 * in UTC, but in some local time: The first time we set the timezone,
145 * we will warp the clock so that it is ticking UTC time instead of
146 * local time. Presumably, if someone is setting the timezone then we
147 * are running in an environment where the programs understand about
148 * timezones. This should be done at boot time in the /etc/rc script,
149 * as soon as possible, so that the clock can be set right. Otherwise,
150 * various programs will get confused when the clock gets warped.
153 int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
155 static int firsttime = 1;
156 int error = 0;
158 if (tv && !timespec_valid(tv))
159 return -EINVAL;
161 error = security_settime(tv, tz);
162 if (error)
163 return error;
165 if (tz) {
166 /* SMP safe, global irq locking makes it work. */
167 sys_tz = *tz;
168 update_vsyscall_tz();
169 if (firsttime) {
170 firsttime = 0;
171 if (!tv)
172 warp_clock();
175 if (tv)
177 /* SMP safe, again the code in arch/foo/time.c should
178 * globally block out interrupts when it runs.
180 return do_settimeofday(tv);
182 return 0;
185 SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
186 struct timezone __user *, tz)
188 struct timeval user_tv;
189 struct timespec new_ts;
190 struct timezone new_tz;
192 if (tv) {
193 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
194 return -EFAULT;
195 new_ts.tv_sec = user_tv.tv_sec;
196 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
198 if (tz) {
199 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
200 return -EFAULT;
203 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
206 SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
208 struct timex txc; /* Local copy of parameter */
209 int ret;
211 /* Copy the user data space into the kernel copy
212 * structure. But bear in mind that the structures
213 * may change
215 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
216 return -EFAULT;
217 ret = do_adjtimex(&txc);
218 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
222 * current_fs_time - Return FS time
223 * @sb: Superblock.
225 * Return the current time truncated to the time granularity supported by
226 * the fs.
228 struct timespec current_fs_time(struct super_block *sb)
230 struct timespec now = current_kernel_time();
231 return timespec_trunc(now, sb->s_time_gran);
233 EXPORT_SYMBOL(current_fs_time);
236 * Convert jiffies to milliseconds and back.
238 * Avoid unnecessary multiplications/divisions in the
239 * two most common HZ cases:
241 unsigned int inline jiffies_to_msecs(const unsigned long j)
243 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
244 return (MSEC_PER_SEC / HZ) * j;
245 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
246 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
247 #else
248 # if BITS_PER_LONG == 32
249 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
250 # else
251 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
252 # endif
253 #endif
255 EXPORT_SYMBOL(jiffies_to_msecs);
257 unsigned int inline jiffies_to_usecs(const unsigned long j)
259 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
260 return (USEC_PER_SEC / HZ) * j;
261 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
262 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
263 #else
264 # if BITS_PER_LONG == 32
265 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
266 # else
267 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
268 # endif
269 #endif
271 EXPORT_SYMBOL(jiffies_to_usecs);
274 * timespec_trunc - Truncate timespec to a granularity
275 * @t: Timespec
276 * @gran: Granularity in ns.
278 * Truncate a timespec to a granularity. gran must be smaller than a second.
279 * Always rounds down.
281 * This function should be only used for timestamps returned by
282 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
283 * it doesn't handle the better resolution of the latter.
285 struct timespec timespec_trunc(struct timespec t, unsigned gran)
288 * Division is pretty slow so avoid it for common cases.
289 * Currently current_kernel_time() never returns better than
290 * jiffies resolution. Exploit that.
292 if (gran <= jiffies_to_usecs(1) * 1000) {
293 /* nothing */
294 } else if (gran == 1000000000) {
295 t.tv_nsec = 0;
296 } else {
297 t.tv_nsec -= t.tv_nsec % gran;
299 return t;
301 EXPORT_SYMBOL(timespec_trunc);
303 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
304 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
305 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
307 * [For the Julian calendar (which was used in Russia before 1917,
308 * Britain & colonies before 1752, anywhere else before 1582,
309 * and is still in use by some communities) leave out the
310 * -year/100+year/400 terms, and add 10.]
312 * This algorithm was first published by Gauss (I think).
314 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
315 * machines where long is 32-bit! (However, as time_t is signed, we
316 * will already get problems at other places on 2038-01-19 03:14:08)
318 unsigned long
319 mktime(const unsigned int year0, const unsigned int mon0,
320 const unsigned int day, const unsigned int hour,
321 const unsigned int min, const unsigned int sec)
323 unsigned int mon = mon0, year = year0;
325 /* 1..12 -> 11,12,1..10 */
326 if (0 >= (int) (mon -= 2)) {
327 mon += 12; /* Puts Feb last since it has leap day */
328 year -= 1;
331 return ((((unsigned long)
332 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
333 year*365 - 719499
334 )*24 + hour /* now have hours */
335 )*60 + min /* now have minutes */
336 )*60 + sec; /* finally seconds */
339 EXPORT_SYMBOL(mktime);
342 * set_normalized_timespec - set timespec sec and nsec parts and normalize
344 * @ts: pointer to timespec variable to be set
345 * @sec: seconds to set
346 * @nsec: nanoseconds to set
348 * Set seconds and nanoseconds field of a timespec variable and
349 * normalize to the timespec storage format
351 * Note: The tv_nsec part is always in the range of
352 * 0 <= tv_nsec < NSEC_PER_SEC
353 * For negative values only the tv_sec field is negative !
355 void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
357 while (nsec >= NSEC_PER_SEC) {
359 * The following asm() prevents the compiler from
360 * optimising this loop into a modulo operation. See
361 * also __iter_div_u64_rem() in include/linux/time.h
363 asm("" : "+rm"(nsec));
364 nsec -= NSEC_PER_SEC;
365 ++sec;
367 while (nsec < 0) {
368 asm("" : "+rm"(nsec));
369 nsec += NSEC_PER_SEC;
370 --sec;
372 ts->tv_sec = sec;
373 ts->tv_nsec = nsec;
375 EXPORT_SYMBOL(set_normalized_timespec);
378 * ns_to_timespec - Convert nanoseconds to timespec
379 * @nsec: the nanoseconds value to be converted
381 * Returns the timespec representation of the nsec parameter.
383 struct timespec ns_to_timespec(const s64 nsec)
385 struct timespec ts;
386 s32 rem;
388 if (!nsec)
389 return (struct timespec) {0, 0};
391 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
392 if (unlikely(rem < 0)) {
393 ts.tv_sec--;
394 rem += NSEC_PER_SEC;
396 ts.tv_nsec = rem;
398 return ts;
400 EXPORT_SYMBOL(ns_to_timespec);
403 * ns_to_timeval - Convert nanoseconds to timeval
404 * @nsec: the nanoseconds value to be converted
406 * Returns the timeval representation of the nsec parameter.
408 struct timeval ns_to_timeval(const s64 nsec)
410 struct timespec ts = ns_to_timespec(nsec);
411 struct timeval tv;
413 tv.tv_sec = ts.tv_sec;
414 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
416 return tv;
418 EXPORT_SYMBOL(ns_to_timeval);
421 * When we convert to jiffies then we interpret incoming values
422 * the following way:
424 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
426 * - 'too large' values [that would result in larger than
427 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
429 * - all other values are converted to jiffies by either multiplying
430 * the input value by a factor or dividing it with a factor
432 * We must also be careful about 32-bit overflows.
434 unsigned long msecs_to_jiffies(const unsigned int m)
437 * Negative value, means infinite timeout:
439 if ((int)m < 0)
440 return MAX_JIFFY_OFFSET;
442 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
444 * HZ is equal to or smaller than 1000, and 1000 is a nice
445 * round multiple of HZ, divide with the factor between them,
446 * but round upwards:
448 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
449 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
451 * HZ is larger than 1000, and HZ is a nice round multiple of
452 * 1000 - simply multiply with the factor between them.
454 * But first make sure the multiplication result cannot
455 * overflow:
457 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
458 return MAX_JIFFY_OFFSET;
460 return m * (HZ / MSEC_PER_SEC);
461 #else
463 * Generic case - multiply, round and divide. But first
464 * check that if we are doing a net multiplication, that
465 * we wouldn't overflow:
467 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
468 return MAX_JIFFY_OFFSET;
470 return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
471 >> MSEC_TO_HZ_SHR32;
472 #endif
474 EXPORT_SYMBOL(msecs_to_jiffies);
476 unsigned long usecs_to_jiffies(const unsigned int u)
478 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
479 return MAX_JIFFY_OFFSET;
480 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
481 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
482 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
483 return u * (HZ / USEC_PER_SEC);
484 #else
485 return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
486 >> USEC_TO_HZ_SHR32;
487 #endif
489 EXPORT_SYMBOL(usecs_to_jiffies);
492 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
493 * that a remainder subtract here would not do the right thing as the
494 * resolution values don't fall on second boundries. I.e. the line:
495 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
497 * Rather, we just shift the bits off the right.
499 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
500 * value to a scaled second value.
502 unsigned long
503 timespec_to_jiffies(const struct timespec *value)
505 unsigned long sec = value->tv_sec;
506 long nsec = value->tv_nsec + TICK_NSEC - 1;
508 if (sec >= MAX_SEC_IN_JIFFIES){
509 sec = MAX_SEC_IN_JIFFIES;
510 nsec = 0;
512 return (((u64)sec * SEC_CONVERSION) +
513 (((u64)nsec * NSEC_CONVERSION) >>
514 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
517 EXPORT_SYMBOL(timespec_to_jiffies);
519 void
520 jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
523 * Convert jiffies to nanoseconds and separate with
524 * one divide.
526 u32 rem;
527 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
528 NSEC_PER_SEC, &rem);
529 value->tv_nsec = rem;
531 EXPORT_SYMBOL(jiffies_to_timespec);
533 /* Same for "timeval"
535 * Well, almost. The problem here is that the real system resolution is
536 * in nanoseconds and the value being converted is in micro seconds.
537 * Also for some machines (those that use HZ = 1024, in-particular),
538 * there is a LARGE error in the tick size in microseconds.
540 * The solution we use is to do the rounding AFTER we convert the
541 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
542 * Instruction wise, this should cost only an additional add with carry
543 * instruction above the way it was done above.
545 unsigned long
546 timeval_to_jiffies(const struct timeval *value)
548 unsigned long sec = value->tv_sec;
549 long usec = value->tv_usec;
551 if (sec >= MAX_SEC_IN_JIFFIES){
552 sec = MAX_SEC_IN_JIFFIES;
553 usec = 0;
555 return (((u64)sec * SEC_CONVERSION) +
556 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
557 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
559 EXPORT_SYMBOL(timeval_to_jiffies);
561 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
564 * Convert jiffies to nanoseconds and separate with
565 * one divide.
567 u32 rem;
569 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
570 NSEC_PER_SEC, &rem);
571 value->tv_usec = rem / NSEC_PER_USEC;
573 EXPORT_SYMBOL(jiffies_to_timeval);
576 * Convert jiffies/jiffies_64 to clock_t and back.
578 clock_t jiffies_to_clock_t(long x)
580 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
581 # if HZ < USER_HZ
582 return x * (USER_HZ / HZ);
583 # else
584 return x / (HZ / USER_HZ);
585 # endif
586 #else
587 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
588 #endif
590 EXPORT_SYMBOL(jiffies_to_clock_t);
592 unsigned long clock_t_to_jiffies(unsigned long x)
594 #if (HZ % USER_HZ)==0
595 if (x >= ~0UL / (HZ / USER_HZ))
596 return ~0UL;
597 return x * (HZ / USER_HZ);
598 #else
599 /* Don't worry about loss of precision here .. */
600 if (x >= ~0UL / HZ * USER_HZ)
601 return ~0UL;
603 /* .. but do try to contain it here */
604 return div_u64((u64)x * HZ, USER_HZ);
605 #endif
607 EXPORT_SYMBOL(clock_t_to_jiffies);
609 u64 jiffies_64_to_clock_t(u64 x)
611 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
612 # if HZ < USER_HZ
613 x = div_u64(x * USER_HZ, HZ);
614 # elif HZ > USER_HZ
615 x = div_u64(x, HZ / USER_HZ);
616 # else
617 /* Nothing to do */
618 # endif
619 #else
621 * There are better ways that don't overflow early,
622 * but even this doesn't overflow in hundreds of years
623 * in 64 bits, so..
625 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
626 #endif
627 return x;
629 EXPORT_SYMBOL(jiffies_64_to_clock_t);
631 u64 nsec_to_clock_t(u64 x)
633 #if (NSEC_PER_SEC % USER_HZ) == 0
634 return div_u64(x, NSEC_PER_SEC / USER_HZ);
635 #elif (USER_HZ % 512) == 0
636 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
637 #else
639 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
640 * overflow after 64.99 years.
641 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
643 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
644 #endif
648 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
650 * @n: nsecs in u64
652 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
653 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
654 * for scheduler, not for use in device drivers to calculate timeout value.
656 * note:
657 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
658 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
660 unsigned long nsecs_to_jiffies(u64 n)
662 #if (NSEC_PER_SEC % HZ) == 0
663 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
664 return div_u64(n, NSEC_PER_SEC / HZ);
665 #elif (HZ % 512) == 0
666 /* overflow after 292 years if HZ = 1024 */
667 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
668 #else
670 * Generic case - optimized for cases where HZ is a multiple of 3.
671 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
673 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
674 #endif
677 #if (BITS_PER_LONG < 64)
678 u64 get_jiffies_64(void)
680 unsigned long seq;
681 u64 ret;
683 do {
684 seq = read_seqbegin(&xtime_lock);
685 ret = jiffies_64;
686 } while (read_seqretry(&xtime_lock, seq));
687 return ret;
689 EXPORT_SYMBOL(get_jiffies_64);
690 #endif
692 EXPORT_SYMBOL(jiffies);
695 * Add two timespec values and do a safety check for overflow.
696 * It's assumed that both values are valid (>= 0)
698 struct timespec timespec_add_safe(const struct timespec lhs,
699 const struct timespec rhs)
701 struct timespec res;
703 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
704 lhs.tv_nsec + rhs.tv_nsec);
706 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
707 res.tv_sec = TIME_T_MAX;
709 return res;