projects/linux·blob v2.6.35 · refs

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1/*
2 * linux/kernel/time.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * This file contains the interface functions for the various
7 * time related system calls: time, stime, gettimeofday, settimeofday,
8 * adjtime
9 */
10/*
11 * Modification history kernel/time.c
12 *
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
28 */
29
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>
40
41#include <asm/uaccess.h>
42#include <asm/unistd.h>
43
44#include "timeconst.h"
45
46/*
47 * The timezone where the local system is located. Used as a default by some
48 * programs who obtain this value by using gettimeofday.
49 */
50struct timezone sys_tz;
51
52EXPORT_SYMBOL(sys_tz);
53
54#ifdef __ARCH_WANT_SYS_TIME
55
56/*
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).
61 */
62SYSCALL_DEFINE1(time, time_t __user *, tloc)
63{
64 time_t i = get_seconds();
65
66 if (tloc) {
67 if (put_user(i,tloc))
68 return -EFAULT;
69 }
70 force_successful_syscall_return();
71 return i;
72}
73
74/*
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).
79 */
80
81SYSCALL_DEFINE1(stime, time_t __user *, tptr)
82{
83 struct timespec tv;
84 int err;
85
86 if (get_user(tv.tv_sec, tptr))
87 return -EFAULT;
88
89 tv.tv_nsec = 0;
90
91 err = security_settime(&tv, NULL);
92 if (err)
93 return err;
94
95 do_settimeofday(&tv);
96 return 0;
97}
98
99#endif /* __ARCH_WANT_SYS_TIME */
100
101SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv,
102 struct timezone __user *, tz)
103{
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;
109 }
110 if (unlikely(tz != NULL)) {
111 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
112 return -EFAULT;
113 }
114 return 0;
115}
116
117/*
118 * Adjust the time obtained from the CMOS to be UTC time instead of
119 * local time.
120 *
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....
126 *
127 * - TYT, 1992-01-01
128 *
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.
132 */
133static inline void warp_clock(void)
134{
135 struct timespec adjust;
136
137 adjust = current_kernel_time();
138 adjust.tv_sec += sys_tz.tz_minuteswest * 60;
139 do_settimeofday(&adjust);
140}
141
142/*
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.
151 */
152
153int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
154{
155 static int firsttime = 1;
156 int error = 0;
157
158 if (tv && !timespec_valid(tv))
159 return -EINVAL;
160
161 error = security_settime(tv, tz);
162 if (error)
163 return error;
164
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();
173 }
174 }
175 if (tv)
176 {
177 /* SMP safe, again the code in arch/foo/time.c should
178 * globally block out interrupts when it runs.
179 */
180 return do_settimeofday(tv);
181 }
182 return 0;
183}
184
185SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
186 struct timezone __user *, tz)
187{
188 struct timeval user_tv;
189 struct timespec new_ts;
190 struct timezone new_tz;
191
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;
197 }
198 if (tz) {
199 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
200 return -EFAULT;
201 }
202
203 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
204}
205
206SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
207{
208 struct timex txc; /* Local copy of parameter */
209 int ret;
210
211 /* Copy the user data space into the kernel copy
212 * structure. But bear in mind that the structures
213 * may change
214 */
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;
219}
220
221/**
222 * current_fs_time - Return FS time
223 * @sb: Superblock.
224 *
225 * Return the current time truncated to the time granularity supported by
226 * the fs.
227 */
228struct timespec current_fs_time(struct super_block *sb)
229{
230 struct timespec now = current_kernel_time();
231 return timespec_trunc(now, sb->s_time_gran);
232}
233EXPORT_SYMBOL(current_fs_time);
234
235/*
236 * Convert jiffies to milliseconds and back.
237 *
238 * Avoid unnecessary multiplications/divisions in the
239 * two most common HZ cases:
240 */
241unsigned int inline jiffies_to_msecs(const unsigned long j)
242{
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
254}
255EXPORT_SYMBOL(jiffies_to_msecs);
256
257unsigned int inline jiffies_to_usecs(const unsigned long j)
258{
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
270}
271EXPORT_SYMBOL(jiffies_to_usecs);
272
273/**
274 * timespec_trunc - Truncate timespec to a granularity
275 * @t: Timespec
276 * @gran: Granularity in ns.
277 *
278 * Truncate a timespec to a granularity. gran must be smaller than a second.
279 * Always rounds down.
280 *
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.
284 */
285struct timespec timespec_trunc(struct timespec t, unsigned gran)
286{
287 /*
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.
291 */
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;
298 }
299 return t;
300}
301EXPORT_SYMBOL(timespec_trunc);
302
303#ifndef CONFIG_GENERIC_TIME
304/*
305 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
306 * and therefore only yields usec accuracy
307 */
308void getnstimeofday(struct timespec *tv)
309{
310 struct timeval x;
311
312 do_gettimeofday(&x);
313 tv->tv_sec = x.tv_sec;
314 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
315}
316EXPORT_SYMBOL_GPL(getnstimeofday);
317#endif
318
319/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
320 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
321 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
322 *
323 * [For the Julian calendar (which was used in Russia before 1917,
324 * Britain & colonies before 1752, anywhere else before 1582,
325 * and is still in use by some communities) leave out the
326 * -year/100+year/400 terms, and add 10.]
327 *
328 * This algorithm was first published by Gauss (I think).
329 *
330 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
331 * machines where long is 32-bit! (However, as time_t is signed, we
332 * will already get problems at other places on 2038-01-19 03:14:08)
333 */
334unsigned long
335mktime(const unsigned int year0, const unsigned int mon0,
336 const unsigned int day, const unsigned int hour,
337 const unsigned int min, const unsigned int sec)
338{
339 unsigned int mon = mon0, year = year0;
340
341 /* 1..12 -> 11,12,1..10 */
342 if (0 >= (int) (mon -= 2)) {
343 mon += 12; /* Puts Feb last since it has leap day */
344 year -= 1;
345 }
346
347 return ((((unsigned long)
348 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
349 year*365 - 719499
350 )*24 + hour /* now have hours */
351 )*60 + min /* now have minutes */
352 )*60 + sec; /* finally seconds */
353}
354
355EXPORT_SYMBOL(mktime);
356
357/**
358 * set_normalized_timespec - set timespec sec and nsec parts and normalize
359 *
360 * @ts: pointer to timespec variable to be set
361 * @sec: seconds to set
362 * @nsec: nanoseconds to set
363 *
364 * Set seconds and nanoseconds field of a timespec variable and
365 * normalize to the timespec storage format
366 *
367 * Note: The tv_nsec part is always in the range of
368 * 0 <= tv_nsec < NSEC_PER_SEC
369 * For negative values only the tv_sec field is negative !
370 */
371void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
372{
373 while (nsec >= NSEC_PER_SEC) {
374 /*
375 * The following asm() prevents the compiler from
376 * optimising this loop into a modulo operation. See
377 * also __iter_div_u64_rem() in include/linux/time.h
378 */
379 asm("" : "+rm"(nsec));
380 nsec -= NSEC_PER_SEC;
381 ++sec;
382 }
383 while (nsec < 0) {
384 asm("" : "+rm"(nsec));
385 nsec += NSEC_PER_SEC;
386 --sec;
387 }
388 ts->tv_sec = sec;
389 ts->tv_nsec = nsec;
390}
391EXPORT_SYMBOL(set_normalized_timespec);
392
393/**
394 * ns_to_timespec - Convert nanoseconds to timespec
395 * @nsec: the nanoseconds value to be converted
396 *
397 * Returns the timespec representation of the nsec parameter.
398 */
399struct timespec ns_to_timespec(const s64 nsec)
400{
401 struct timespec ts;
402 s32 rem;
403
404 if (!nsec)
405 return (struct timespec) {0, 0};
406
407 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
408 if (unlikely(rem < 0)) {
409 ts.tv_sec--;
410 rem += NSEC_PER_SEC;
411 }
412 ts.tv_nsec = rem;
413
414 return ts;
415}
416EXPORT_SYMBOL(ns_to_timespec);
417
418/**
419 * ns_to_timeval - Convert nanoseconds to timeval
420 * @nsec: the nanoseconds value to be converted
421 *
422 * Returns the timeval representation of the nsec parameter.
423 */
424struct timeval ns_to_timeval(const s64 nsec)
425{
426 struct timespec ts = ns_to_timespec(nsec);
427 struct timeval tv;
428
429 tv.tv_sec = ts.tv_sec;
430 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
431
432 return tv;
433}
434EXPORT_SYMBOL(ns_to_timeval);
435
436/*
437 * When we convert to jiffies then we interpret incoming values
438 * the following way:
439 *
440 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
441 *
442 * - 'too large' values [that would result in larger than
443 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
444 *
445 * - all other values are converted to jiffies by either multiplying
446 * the input value by a factor or dividing it with a factor
447 *
448 * We must also be careful about 32-bit overflows.
449 */
450unsigned long msecs_to_jiffies(const unsigned int m)
451{
452 /*
453 * Negative value, means infinite timeout:
454 */
455 if ((int)m < 0)
456 return MAX_JIFFY_OFFSET;
457
458#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
459 /*
460 * HZ is equal to or smaller than 1000, and 1000 is a nice
461 * round multiple of HZ, divide with the factor between them,
462 * but round upwards:
463 */
464 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
465#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
466 /*
467 * HZ is larger than 1000, and HZ is a nice round multiple of
468 * 1000 - simply multiply with the factor between them.
469 *
470 * But first make sure the multiplication result cannot
471 * overflow:
472 */
473 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
474 return MAX_JIFFY_OFFSET;
475
476 return m * (HZ / MSEC_PER_SEC);
477#else
478 /*
479 * Generic case - multiply, round and divide. But first
480 * check that if we are doing a net multiplication, that
481 * we wouldn't overflow:
482 */
483 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
484 return MAX_JIFFY_OFFSET;
485
486 return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
487 >> MSEC_TO_HZ_SHR32;
488#endif
489}
490EXPORT_SYMBOL(msecs_to_jiffies);
491
492unsigned long usecs_to_jiffies(const unsigned int u)
493{
494 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
495 return MAX_JIFFY_OFFSET;
496#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
497 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
498#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
499 return u * (HZ / USEC_PER_SEC);
500#else
501 return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
502 >> USEC_TO_HZ_SHR32;
503#endif
504}
505EXPORT_SYMBOL(usecs_to_jiffies);
506
507/*
508 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
509 * that a remainder subtract here would not do the right thing as the
510 * resolution values don't fall on second boundries. I.e. the line:
511 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
512 *
513 * Rather, we just shift the bits off the right.
514 *
515 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
516 * value to a scaled second value.
517 */
518unsigned long
519timespec_to_jiffies(const struct timespec *value)
520{
521 unsigned long sec = value->tv_sec;
522 long nsec = value->tv_nsec + TICK_NSEC - 1;
523
524 if (sec >= MAX_SEC_IN_JIFFIES){
525 sec = MAX_SEC_IN_JIFFIES;
526 nsec = 0;
527 }
528 return (((u64)sec * SEC_CONVERSION) +
529 (((u64)nsec * NSEC_CONVERSION) >>
530 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
531
532}
533EXPORT_SYMBOL(timespec_to_jiffies);
534
535void
536jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
537{
538 /*
539 * Convert jiffies to nanoseconds and separate with
540 * one divide.
541 */
542 u32 rem;
543 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
544 NSEC_PER_SEC, &rem);
545 value->tv_nsec = rem;
546}
547EXPORT_SYMBOL(jiffies_to_timespec);
548
549/* Same for "timeval"
550 *
551 * Well, almost. The problem here is that the real system resolution is
552 * in nanoseconds and the value being converted is in micro seconds.
553 * Also for some machines (those that use HZ = 1024, in-particular),
554 * there is a LARGE error in the tick size in microseconds.
555
556 * The solution we use is to do the rounding AFTER we convert the
557 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
558 * Instruction wise, this should cost only an additional add with carry
559 * instruction above the way it was done above.
560 */
561unsigned long
562timeval_to_jiffies(const struct timeval *value)
563{
564 unsigned long sec = value->tv_sec;
565 long usec = value->tv_usec;
566
567 if (sec >= MAX_SEC_IN_JIFFIES){
568 sec = MAX_SEC_IN_JIFFIES;
569 usec = 0;
570 }
571 return (((u64)sec * SEC_CONVERSION) +
572 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
573 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
574}
575EXPORT_SYMBOL(timeval_to_jiffies);
576
577void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
578{
579 /*
580 * Convert jiffies to nanoseconds and separate with
581 * one divide.
582 */
583 u32 rem;
584
585 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
586 NSEC_PER_SEC, &rem);
587 value->tv_usec = rem / NSEC_PER_USEC;
588}
589EXPORT_SYMBOL(jiffies_to_timeval);
590
591/*
592 * Convert jiffies/jiffies_64 to clock_t and back.
593 */
594clock_t jiffies_to_clock_t(long x)
595{
596#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
597# if HZ < USER_HZ
598 return x * (USER_HZ / HZ);
599# else
600 return x / (HZ / USER_HZ);
601# endif
602#else
603 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
604#endif
605}
606EXPORT_SYMBOL(jiffies_to_clock_t);
607
608unsigned long clock_t_to_jiffies(unsigned long x)
609{
610#if (HZ % USER_HZ)==0
611 if (x >= ~0UL / (HZ / USER_HZ))
612 return ~0UL;
613 return x * (HZ / USER_HZ);
614#else
615 /* Don't worry about loss of precision here .. */
616 if (x >= ~0UL / HZ * USER_HZ)
617 return ~0UL;
618
619 /* .. but do try to contain it here */
620 return div_u64((u64)x * HZ, USER_HZ);
621#endif
622}
623EXPORT_SYMBOL(clock_t_to_jiffies);
624
625u64 jiffies_64_to_clock_t(u64 x)
626{
627#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
628# if HZ < USER_HZ
629 x = div_u64(x * USER_HZ, HZ);
630# elif HZ > USER_HZ
631 x = div_u64(x, HZ / USER_HZ);
632# else
633 /* Nothing to do */
634# endif
635#else
636 /*
637 * There are better ways that don't overflow early,
638 * but even this doesn't overflow in hundreds of years
639 * in 64 bits, so..
640 */
641 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
642#endif
643 return x;
644}
645EXPORT_SYMBOL(jiffies_64_to_clock_t);
646
647u64 nsec_to_clock_t(u64 x)
648{
649#if (NSEC_PER_SEC % USER_HZ) == 0
650 return div_u64(x, NSEC_PER_SEC / USER_HZ);
651#elif (USER_HZ % 512) == 0
652 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
653#else
654 /*
655 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
656 * overflow after 64.99 years.
657 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
658 */
659 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
660#endif
661}
662
663/**
664 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
665 *
666 * @n: nsecs in u64
667 *
668 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
669 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
670 * for scheduler, not for use in device drivers to calculate timeout value.
671 *
672 * note:
673 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
674 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
675 */
676unsigned long nsecs_to_jiffies(u64 n)
677{
678#if (NSEC_PER_SEC % HZ) == 0
679 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
680 return div_u64(n, NSEC_PER_SEC / HZ);
681#elif (HZ % 512) == 0
682 /* overflow after 292 years if HZ = 1024 */
683 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
684#else
685 /*
686 * Generic case - optimized for cases where HZ is a multiple of 3.
687 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
688 */
689 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
690#endif
691}
692
693#if (BITS_PER_LONG < 64)
694u64 get_jiffies_64(void)
695{
696 unsigned long seq;
697 u64 ret;
698
699 do {
700 seq = read_seqbegin(&xtime_lock);
701 ret = jiffies_64;
702 } while (read_seqretry(&xtime_lock, seq));
703 return ret;
704}
705EXPORT_SYMBOL(get_jiffies_64);
706#endif
707
708EXPORT_SYMBOL(jiffies);
709
710/*
711 * Add two timespec values and do a safety check for overflow.
712 * It's assumed that both values are valid (>= 0)
713 */
714struct timespec timespec_add_safe(const struct timespec lhs,
715 const struct timespec rhs)
716{
717 struct timespec res;
718
719 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
720 lhs.tv_nsec + rhs.tv_nsec);
721
722 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
723 res.tv_sec = TIME_T_MAX;
724
725 return res;
726}