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[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / time.c
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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/errno.h>
34 #include <linux/syscalls.h>
35 #include <linux/security.h>
36 #include <linux/fs.h>
37 #include <linux/module.h>
39 #include <asm/uaccess.h>
40 #include <asm/unistd.h>
42 /*
43 * The timezone where the local system is located. Used as a default by some
44 * programs who obtain this value by using gettimeofday.
46 struct timezone sys_tz;
48 EXPORT_SYMBOL(sys_tz);
50 #ifdef __ARCH_WANT_SYS_TIME
53 * sys_time() can be implemented in user-level using
54 * sys_gettimeofday(). Is this for backwards compatibility? If so,
55 * why not move it into the appropriate arch directory (for those
56 * architectures that need it).
58 asmlinkage long sys_time(time_t __user * tloc)
60 time_t i;
61 struct timespec tv;
63 getnstimeofday(&tv);
64 i = tv.tv_sec;
66 if (tloc) {
67 if (put_user(i,tloc))
68 i = -EFAULT;
70 return i;
74 * sys_stime() can be implemented in user-level using
75 * sys_settimeofday(). Is this for backwards compatibility? If so,
76 * why not move it into the appropriate arch directory (for those
77 * architectures that need it).
80 asmlinkage long sys_stime(time_t __user *tptr)
82 struct timespec tv;
83 int err;
85 if (get_user(tv.tv_sec, tptr))
86 return -EFAULT;
88 tv.tv_nsec = 0;
90 err = security_settime(&tv, NULL);
91 if (err)
92 return err;
94 do_settimeofday(&tv);
95 return 0;
98 #endif /* __ARCH_WANT_SYS_TIME */
100 asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
102 if (likely(tv != NULL)) {
103 struct timeval ktv;
104 do_gettimeofday(&ktv);
105 if (copy_to_user(tv, &ktv, sizeof(ktv)))
106 return -EFAULT;
108 if (unlikely(tz != NULL)) {
109 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
110 return -EFAULT;
112 return 0;
116 * Adjust the time obtained from the CMOS to be UTC time instead of
117 * local time.
119 * This is ugly, but preferable to the alternatives. Otherwise we
120 * would either need to write a program to do it in /etc/rc (and risk
121 * confusion if the program gets run more than once; it would also be
122 * hard to make the program warp the clock precisely n hours) or
123 * compile in the timezone information into the kernel. Bad, bad....
125 * - TYT, 1992-01-01
127 * The best thing to do is to keep the CMOS clock in universal time (UTC)
128 * as real UNIX machines always do it. This avoids all headaches about
129 * daylight saving times and warping kernel clocks.
131 static inline void warp_clock(void)
133 write_seqlock_irq(&xtime_lock);
134 wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
135 xtime.tv_sec += sys_tz.tz_minuteswest * 60;
136 write_sequnlock_irq(&xtime_lock);
137 clock_was_set();
141 * In case for some reason the CMOS clock has not already been running
142 * in UTC, but in some local time: The first time we set the timezone,
143 * we will warp the clock so that it is ticking UTC time instead of
144 * local time. Presumably, if someone is setting the timezone then we
145 * are running in an environment where the programs understand about
146 * timezones. This should be done at boot time in the /etc/rc script,
147 * as soon as possible, so that the clock can be set right. Otherwise,
148 * various programs will get confused when the clock gets warped.
151 int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
153 static int firsttime = 1;
154 int error = 0;
156 if (tv && !timespec_valid(tv))
157 return -EINVAL;
159 error = security_settime(tv, tz);
160 if (error)
161 return error;
163 if (tz) {
164 /* SMP safe, global irq locking makes it work. */
165 sys_tz = *tz;
166 if (firsttime) {
167 firsttime = 0;
168 if (!tv)
169 warp_clock();
172 if (tv)
174 /* SMP safe, again the code in arch/foo/time.c should
175 * globally block out interrupts when it runs.
177 return do_settimeofday(tv);
179 return 0;
182 asmlinkage long sys_settimeofday(struct timeval __user *tv,
183 struct timezone __user *tz)
185 struct timeval user_tv;
186 struct timespec new_ts;
187 struct timezone new_tz;
189 if (tv) {
190 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
191 return -EFAULT;
192 new_ts.tv_sec = user_tv.tv_sec;
193 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
195 if (tz) {
196 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
197 return -EFAULT;
200 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
203 asmlinkage long sys_adjtimex(struct timex __user *txc_p)
205 struct timex txc; /* Local copy of parameter */
206 int ret;
208 /* Copy the user data space into the kernel copy
209 * structure. But bear in mind that the structures
210 * may change
212 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
213 return -EFAULT;
214 ret = do_adjtimex(&txc);
215 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
219 * current_fs_time - Return FS time
220 * @sb: Superblock.
222 * Return the current time truncated to the time granularity supported by
223 * the fs.
225 struct timespec current_fs_time(struct super_block *sb)
227 struct timespec now = current_kernel_time();
228 return timespec_trunc(now, sb->s_time_gran);
230 EXPORT_SYMBOL(current_fs_time);
233 * Convert jiffies to milliseconds and back.
235 * Avoid unnecessary multiplications/divisions in the
236 * two most common HZ cases:
238 unsigned int inline jiffies_to_msecs(const unsigned long j)
240 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
241 return (MSEC_PER_SEC / HZ) * j;
242 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
243 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
244 #else
245 return (j * MSEC_PER_SEC) / HZ;
246 #endif
248 EXPORT_SYMBOL(jiffies_to_msecs);
250 unsigned int inline jiffies_to_usecs(const unsigned long j)
252 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
253 return (USEC_PER_SEC / HZ) * j;
254 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
255 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
256 #else
257 return (j * USEC_PER_SEC) / HZ;
258 #endif
260 EXPORT_SYMBOL(jiffies_to_usecs);
263 * timespec_trunc - Truncate timespec to a granularity
264 * @t: Timespec
265 * @gran: Granularity in ns.
267 * Truncate a timespec to a granularity. gran must be smaller than a second.
268 * Always rounds down.
270 * This function should be only used for timestamps returned by
271 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
272 * it doesn't handle the better resolution of the later.
274 struct timespec timespec_trunc(struct timespec t, unsigned gran)
277 * Division is pretty slow so avoid it for common cases.
278 * Currently current_kernel_time() never returns better than
279 * jiffies resolution. Exploit that.
281 if (gran <= jiffies_to_usecs(1) * 1000) {
282 /* nothing */
283 } else if (gran == 1000000000) {
284 t.tv_nsec = 0;
285 } else {
286 t.tv_nsec -= t.tv_nsec % gran;
288 return t;
290 EXPORT_SYMBOL(timespec_trunc);
292 #ifndef CONFIG_GENERIC_TIME
294 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
295 * and therefore only yields usec accuracy
297 void getnstimeofday(struct timespec *tv)
299 struct timeval x;
301 do_gettimeofday(&x);
302 tv->tv_sec = x.tv_sec;
303 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
305 EXPORT_SYMBOL_GPL(getnstimeofday);
306 #endif
308 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
309 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
310 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
312 * [For the Julian calendar (which was used in Russia before 1917,
313 * Britain & colonies before 1752, anywhere else before 1582,
314 * and is still in use by some communities) leave out the
315 * -year/100+year/400 terms, and add 10.]
317 * This algorithm was first published by Gauss (I think).
319 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
320 * machines were long is 32-bit! (However, as time_t is signed, we
321 * will already get problems at other places on 2038-01-19 03:14:08)
323 unsigned long
324 mktime(const unsigned int year0, const unsigned int mon0,
325 const unsigned int day, const unsigned int hour,
326 const unsigned int min, const unsigned int sec)
328 unsigned int mon = mon0, year = year0;
330 /* 1..12 -> 11,12,1..10 */
331 if (0 >= (int) (mon -= 2)) {
332 mon += 12; /* Puts Feb last since it has leap day */
333 year -= 1;
336 return ((((unsigned long)
337 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
338 year*365 - 719499
339 )*24 + hour /* now have hours */
340 )*60 + min /* now have minutes */
341 )*60 + sec; /* finally seconds */
344 EXPORT_SYMBOL(mktime);
347 * set_normalized_timespec - set timespec sec and nsec parts and normalize
349 * @ts: pointer to timespec variable to be set
350 * @sec: seconds to set
351 * @nsec: nanoseconds to set
353 * Set seconds and nanoseconds field of a timespec variable and
354 * normalize to the timespec storage format
356 * Note: The tv_nsec part is always in the range of
357 * 0 <= tv_nsec < NSEC_PER_SEC
358 * For negative values only the tv_sec field is negative !
360 void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
362 while (nsec >= NSEC_PER_SEC) {
363 nsec -= NSEC_PER_SEC;
364 ++sec;
366 while (nsec < 0) {
367 nsec += NSEC_PER_SEC;
368 --sec;
370 ts->tv_sec = sec;
371 ts->tv_nsec = nsec;
375 * ns_to_timespec - Convert nanoseconds to timespec
376 * @nsec: the nanoseconds value to be converted
378 * Returns the timespec representation of the nsec parameter.
380 struct timespec ns_to_timespec(const s64 nsec)
382 struct timespec ts;
384 if (!nsec)
385 return (struct timespec) {0, 0};
387 ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC, &ts.tv_nsec);
388 if (unlikely(nsec < 0))
389 set_normalized_timespec(&ts, ts.tv_sec, ts.tv_nsec);
391 return ts;
393 EXPORT_SYMBOL(ns_to_timespec);
396 * ns_to_timeval - Convert nanoseconds to timeval
397 * @nsec: the nanoseconds value to be converted
399 * Returns the timeval representation of the nsec parameter.
401 struct timeval ns_to_timeval(const s64 nsec)
403 struct timespec ts = ns_to_timespec(nsec);
404 struct timeval tv;
406 tv.tv_sec = ts.tv_sec;
407 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
409 return tv;
411 EXPORT_SYMBOL(ns_to_timeval);
414 * When we convert to jiffies then we interpret incoming values
415 * the following way:
417 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
419 * - 'too large' values [that would result in larger than
420 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
422 * - all other values are converted to jiffies by either multiplying
423 * the input value by a factor or dividing it with a factor
425 * We must also be careful about 32-bit overflows.
427 unsigned long msecs_to_jiffies(const unsigned int m)
430 * Negative value, means infinite timeout:
432 if ((int)m < 0)
433 return MAX_JIFFY_OFFSET;
435 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
437 * HZ is equal to or smaller than 1000, and 1000 is a nice
438 * round multiple of HZ, divide with the factor between them,
439 * but round upwards:
441 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
442 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
444 * HZ is larger than 1000, and HZ is a nice round multiple of
445 * 1000 - simply multiply with the factor between them.
447 * But first make sure the multiplication result cannot
448 * overflow:
450 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
451 return MAX_JIFFY_OFFSET;
453 return m * (HZ / MSEC_PER_SEC);
454 #else
456 * Generic case - multiply, round and divide. But first
457 * check that if we are doing a net multiplication, that
458 * we wouldnt overflow:
460 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
461 return MAX_JIFFY_OFFSET;
463 return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
464 #endif
466 EXPORT_SYMBOL(msecs_to_jiffies);
468 unsigned long usecs_to_jiffies(const unsigned int u)
470 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
471 return MAX_JIFFY_OFFSET;
472 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
473 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
474 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
475 return u * (HZ / USEC_PER_SEC);
476 #else
477 return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC;
478 #endif
480 EXPORT_SYMBOL(usecs_to_jiffies);
483 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
484 * that a remainder subtract here would not do the right thing as the
485 * resolution values don't fall on second boundries. I.e. the line:
486 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
488 * Rather, we just shift the bits off the right.
490 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
491 * value to a scaled second value.
493 unsigned long
494 timespec_to_jiffies(const struct timespec *value)
496 unsigned long sec = value->tv_sec;
497 long nsec = value->tv_nsec + TICK_NSEC - 1;
499 if (sec >= MAX_SEC_IN_JIFFIES){
500 sec = MAX_SEC_IN_JIFFIES;
501 nsec = 0;
503 return (((u64)sec * SEC_CONVERSION) +
504 (((u64)nsec * NSEC_CONVERSION) >>
505 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
508 EXPORT_SYMBOL(timespec_to_jiffies);
510 void
511 jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
514 * Convert jiffies to nanoseconds and separate with
515 * one divide.
517 u64 nsec = (u64)jiffies * TICK_NSEC;
518 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec);
520 EXPORT_SYMBOL(jiffies_to_timespec);
522 /* Same for "timeval"
524 * Well, almost. The problem here is that the real system resolution is
525 * in nanoseconds and the value being converted is in micro seconds.
526 * Also for some machines (those that use HZ = 1024, in-particular),
527 * there is a LARGE error in the tick size in microseconds.
529 * The solution we use is to do the rounding AFTER we convert the
530 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
531 * Instruction wise, this should cost only an additional add with carry
532 * instruction above the way it was done above.
534 unsigned long
535 timeval_to_jiffies(const struct timeval *value)
537 unsigned long sec = value->tv_sec;
538 long usec = value->tv_usec;
540 if (sec >= MAX_SEC_IN_JIFFIES){
541 sec = MAX_SEC_IN_JIFFIES;
542 usec = 0;
544 return (((u64)sec * SEC_CONVERSION) +
545 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
546 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
548 EXPORT_SYMBOL(timeval_to_jiffies);
550 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
553 * Convert jiffies to nanoseconds and separate with
554 * one divide.
556 u64 nsec = (u64)jiffies * TICK_NSEC;
557 long tv_usec;
559 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &tv_usec);
560 tv_usec /= NSEC_PER_USEC;
561 value->tv_usec = tv_usec;
563 EXPORT_SYMBOL(jiffies_to_timeval);
566 * Convert jiffies/jiffies_64 to clock_t and back.
568 clock_t jiffies_to_clock_t(long x)
570 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
571 return x / (HZ / USER_HZ);
572 #else
573 u64 tmp = (u64)x * TICK_NSEC;
574 do_div(tmp, (NSEC_PER_SEC / USER_HZ));
575 return (long)tmp;
576 #endif
578 EXPORT_SYMBOL(jiffies_to_clock_t);
580 unsigned long clock_t_to_jiffies(unsigned long x)
582 #if (HZ % USER_HZ)==0
583 if (x >= ~0UL / (HZ / USER_HZ))
584 return ~0UL;
585 return x * (HZ / USER_HZ);
586 #else
587 u64 jif;
589 /* Don't worry about loss of precision here .. */
590 if (x >= ~0UL / HZ * USER_HZ)
591 return ~0UL;
593 /* .. but do try to contain it here */
594 jif = x * (u64) HZ;
595 do_div(jif, USER_HZ);
596 return jif;
597 #endif
599 EXPORT_SYMBOL(clock_t_to_jiffies);
601 u64 jiffies_64_to_clock_t(u64 x)
603 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
604 do_div(x, HZ / USER_HZ);
605 #else
607 * There are better ways that don't overflow early,
608 * but even this doesn't overflow in hundreds of years
609 * in 64 bits, so..
611 x *= TICK_NSEC;
612 do_div(x, (NSEC_PER_SEC / USER_HZ));
613 #endif
614 return x;
617 EXPORT_SYMBOL(jiffies_64_to_clock_t);
619 u64 nsec_to_clock_t(u64 x)
621 #if (NSEC_PER_SEC % USER_HZ) == 0
622 do_div(x, (NSEC_PER_SEC / USER_HZ));
623 #elif (USER_HZ % 512) == 0
624 x *= USER_HZ/512;
625 do_div(x, (NSEC_PER_SEC / 512));
626 #else
628 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
629 * overflow after 64.99 years.
630 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
632 x *= 9;
633 do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) /
634 USER_HZ));
635 #endif
636 return x;
639 #if (BITS_PER_LONG < 64)
640 u64 get_jiffies_64(void)
642 unsigned long seq;
643 u64 ret;
645 do {
646 seq = read_seqbegin(&xtime_lock);
647 ret = jiffies_64;
648 } while (read_seqretry(&xtime_lock, seq));
649 return ret;
652 EXPORT_SYMBOL(get_jiffies_64);
653 #endif
655 EXPORT_SYMBOL(jiffies);