Merge tag 'ntb-3.15' of git://github.com/jonmason/ntb
[linux-2.6-block.git] / kernel / time.c
CommitLineData
1da177e4
LT
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
6fa6c3b1 12 *
1da177e4 13 * 1993-09-02 Philip Gladstone
0a0fca9d 14 * Created file with time related functions from sched/core.c and adjtimex()
1da177e4
LT
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
9984de1a 30#include <linux/export.h>
1da177e4 31#include <linux/timex.h>
c59ede7b 32#include <linux/capability.h>
189374ae 33#include <linux/timekeeper_internal.h>
1da177e4 34#include <linux/errno.h>
1da177e4
LT
35#include <linux/syscalls.h>
36#include <linux/security.h>
37#include <linux/fs.h>
71abb3af 38#include <linux/math64.h>
e3d5a27d 39#include <linux/ptrace.h>
1da177e4
LT
40
41#include <asm/uaccess.h>
42#include <asm/unistd.h>
43
bdc80787
PA
44#include "timeconst.h"
45
6fa6c3b1 46/*
1da177e4
LT
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 */
58fd3aa2 62SYSCALL_DEFINE1(time, time_t __user *, tloc)
1da177e4 63{
f20bf612 64 time_t i = get_seconds();
1da177e4
LT
65
66 if (tloc) {
20082208 67 if (put_user(i,tloc))
e3d5a27d 68 return -EFAULT;
1da177e4 69 }
e3d5a27d 70 force_successful_syscall_return();
1da177e4
LT
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 */
6fa6c3b1 80
58fd3aa2 81SYSCALL_DEFINE1(stime, time_t __user *, tptr)
1da177e4
LT
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
58fd3aa2
HC
101SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv,
102 struct timezone __user *, tz)
1da177e4
LT
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
84e345e4
PB
117/*
118 * Indicates if there is an offset between the system clock and the hardware
119 * clock/persistent clock/rtc.
120 */
121int persistent_clock_is_local;
122
1da177e4
LT
123/*
124 * Adjust the time obtained from the CMOS to be UTC time instead of
125 * local time.
6fa6c3b1 126 *
1da177e4
LT
127 * This is ugly, but preferable to the alternatives. Otherwise we
128 * would either need to write a program to do it in /etc/rc (and risk
6fa6c3b1 129 * confusion if the program gets run more than once; it would also be
1da177e4
LT
130 * hard to make the program warp the clock precisely n hours) or
131 * compile in the timezone information into the kernel. Bad, bad....
132 *
bdc80787 133 * - TYT, 1992-01-01
1da177e4
LT
134 *
135 * The best thing to do is to keep the CMOS clock in universal time (UTC)
136 * as real UNIX machines always do it. This avoids all headaches about
137 * daylight saving times and warping kernel clocks.
138 */
77933d72 139static inline void warp_clock(void)
1da177e4 140{
c30bd099
DZ
141 if (sys_tz.tz_minuteswest != 0) {
142 struct timespec adjust;
bd45b7a3 143
84e345e4 144 persistent_clock_is_local = 1;
7859e404
JS
145 adjust.tv_sec = sys_tz.tz_minuteswest * 60;
146 adjust.tv_nsec = 0;
147 timekeeping_inject_offset(&adjust);
c30bd099 148 }
1da177e4
LT
149}
150
151/*
152 * In case for some reason the CMOS clock has not already been running
153 * in UTC, but in some local time: The first time we set the timezone,
154 * we will warp the clock so that it is ticking UTC time instead of
155 * local time. Presumably, if someone is setting the timezone then we
156 * are running in an environment where the programs understand about
157 * timezones. This should be done at boot time in the /etc/rc script,
158 * as soon as possible, so that the clock can be set right. Otherwise,
159 * various programs will get confused when the clock gets warped.
160 */
161
1e6d7679 162int do_sys_settimeofday(const struct timespec *tv, const struct timezone *tz)
1da177e4
LT
163{
164 static int firsttime = 1;
165 int error = 0;
166
951069e3 167 if (tv && !timespec_valid(tv))
718bcceb
TG
168 return -EINVAL;
169
1da177e4
LT
170 error = security_settime(tv, tz);
171 if (error)
172 return error;
173
174 if (tz) {
1da177e4 175 sys_tz = *tz;
2c622148 176 update_vsyscall_tz();
1da177e4
LT
177 if (firsttime) {
178 firsttime = 0;
179 if (!tv)
180 warp_clock();
181 }
182 }
183 if (tv)
1da177e4 184 return do_settimeofday(tv);
1da177e4
LT
185 return 0;
186}
187
58fd3aa2
HC
188SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
189 struct timezone __user *, tz)
1da177e4
LT
190{
191 struct timeval user_tv;
192 struct timespec new_ts;
193 struct timezone new_tz;
194
195 if (tv) {
196 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
197 return -EFAULT;
198 new_ts.tv_sec = user_tv.tv_sec;
199 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
200 }
201 if (tz) {
202 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
203 return -EFAULT;
204 }
205
206 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
207}
208
58fd3aa2 209SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
1da177e4
LT
210{
211 struct timex txc; /* Local copy of parameter */
212 int ret;
213
214 /* Copy the user data space into the kernel copy
215 * structure. But bear in mind that the structures
216 * may change
217 */
218 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
219 return -EFAULT;
220 ret = do_adjtimex(&txc);
221 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
222}
223
1da177e4
LT
224/**
225 * current_fs_time - Return FS time
226 * @sb: Superblock.
227 *
8ba8e95e 228 * Return the current time truncated to the time granularity supported by
1da177e4
LT
229 * the fs.
230 */
231struct timespec current_fs_time(struct super_block *sb)
232{
233 struct timespec now = current_kernel_time();
234 return timespec_trunc(now, sb->s_time_gran);
235}
236EXPORT_SYMBOL(current_fs_time);
237
753e9c5c
ED
238/*
239 * Convert jiffies to milliseconds and back.
240 *
241 * Avoid unnecessary multiplications/divisions in the
242 * two most common HZ cases:
243 */
af3b5628 244unsigned int jiffies_to_msecs(const unsigned long j)
753e9c5c
ED
245{
246#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
247 return (MSEC_PER_SEC / HZ) * j;
248#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
249 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
250#else
bdc80787 251# if BITS_PER_LONG == 32
b9095fd8 252 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
bdc80787
PA
253# else
254 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
255# endif
753e9c5c
ED
256#endif
257}
258EXPORT_SYMBOL(jiffies_to_msecs);
259
af3b5628 260unsigned int jiffies_to_usecs(const unsigned long j)
753e9c5c
ED
261{
262#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
263 return (USEC_PER_SEC / HZ) * j;
264#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
265 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
266#else
bdc80787 267# if BITS_PER_LONG == 32
b9095fd8 268 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
bdc80787
PA
269# else
270 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
271# endif
753e9c5c
ED
272#endif
273}
274EXPORT_SYMBOL(jiffies_to_usecs);
275
1da177e4 276/**
8ba8e95e 277 * timespec_trunc - Truncate timespec to a granularity
1da177e4 278 * @t: Timespec
8ba8e95e 279 * @gran: Granularity in ns.
1da177e4 280 *
8ba8e95e 281 * Truncate a timespec to a granularity. gran must be smaller than a second.
1da177e4
LT
282 * Always rounds down.
283 *
284 * This function should be only used for timestamps returned by
285 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
3eb05676 286 * it doesn't handle the better resolution of the latter.
1da177e4
LT
287 */
288struct timespec timespec_trunc(struct timespec t, unsigned gran)
289{
290 /*
291 * Division is pretty slow so avoid it for common cases.
292 * Currently current_kernel_time() never returns better than
293 * jiffies resolution. Exploit that.
294 */
295 if (gran <= jiffies_to_usecs(1) * 1000) {
296 /* nothing */
297 } else if (gran == 1000000000) {
298 t.tv_nsec = 0;
299 } else {
300 t.tv_nsec -= t.tv_nsec % gran;
301 }
302 return t;
303}
304EXPORT_SYMBOL(timespec_trunc);
305
753be622
TG
306/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
307 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
308 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
309 *
310 * [For the Julian calendar (which was used in Russia before 1917,
311 * Britain & colonies before 1752, anywhere else before 1582,
312 * and is still in use by some communities) leave out the
313 * -year/100+year/400 terms, and add 10.]
314 *
315 * This algorithm was first published by Gauss (I think).
316 *
317 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
3eb05676 318 * machines where long is 32-bit! (However, as time_t is signed, we
753be622
TG
319 * will already get problems at other places on 2038-01-19 03:14:08)
320 */
321unsigned long
f4818900
IM
322mktime(const unsigned int year0, const unsigned int mon0,
323 const unsigned int day, const unsigned int hour,
324 const unsigned int min, const unsigned int sec)
753be622 325{
f4818900
IM
326 unsigned int mon = mon0, year = year0;
327
328 /* 1..12 -> 11,12,1..10 */
329 if (0 >= (int) (mon -= 2)) {
330 mon += 12; /* Puts Feb last since it has leap day */
753be622
TG
331 year -= 1;
332 }
333
334 return ((((unsigned long)
335 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
336 year*365 - 719499
337 )*24 + hour /* now have hours */
338 )*60 + min /* now have minutes */
339 )*60 + sec; /* finally seconds */
340}
341
199e7056
AM
342EXPORT_SYMBOL(mktime);
343
753be622
TG
344/**
345 * set_normalized_timespec - set timespec sec and nsec parts and normalize
346 *
347 * @ts: pointer to timespec variable to be set
348 * @sec: seconds to set
349 * @nsec: nanoseconds to set
350 *
351 * Set seconds and nanoseconds field of a timespec variable and
352 * normalize to the timespec storage format
353 *
354 * Note: The tv_nsec part is always in the range of
bdc80787 355 * 0 <= tv_nsec < NSEC_PER_SEC
753be622
TG
356 * For negative values only the tv_sec field is negative !
357 */
12e09337 358void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
753be622
TG
359{
360 while (nsec >= NSEC_PER_SEC) {
12e09337
TG
361 /*
362 * The following asm() prevents the compiler from
363 * optimising this loop into a modulo operation. See
364 * also __iter_div_u64_rem() in include/linux/time.h
365 */
366 asm("" : "+rm"(nsec));
753be622
TG
367 nsec -= NSEC_PER_SEC;
368 ++sec;
369 }
370 while (nsec < 0) {
12e09337 371 asm("" : "+rm"(nsec));
753be622
TG
372 nsec += NSEC_PER_SEC;
373 --sec;
374 }
375 ts->tv_sec = sec;
376 ts->tv_nsec = nsec;
377}
7c3f944e 378EXPORT_SYMBOL(set_normalized_timespec);
753be622 379
f8f46da3
TG
380/**
381 * ns_to_timespec - Convert nanoseconds to timespec
382 * @nsec: the nanoseconds value to be converted
383 *
384 * Returns the timespec representation of the nsec parameter.
385 */
df869b63 386struct timespec ns_to_timespec(const s64 nsec)
f8f46da3
TG
387{
388 struct timespec ts;
f8bd2258 389 s32 rem;
f8f46da3 390
88fc3897
GA
391 if (!nsec)
392 return (struct timespec) {0, 0};
393
f8bd2258
RZ
394 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
395 if (unlikely(rem < 0)) {
396 ts.tv_sec--;
397 rem += NSEC_PER_SEC;
398 }
399 ts.tv_nsec = rem;
f8f46da3
TG
400
401 return ts;
402}
85795d64 403EXPORT_SYMBOL(ns_to_timespec);
f8f46da3
TG
404
405/**
406 * ns_to_timeval - Convert nanoseconds to timeval
407 * @nsec: the nanoseconds value to be converted
408 *
409 * Returns the timeval representation of the nsec parameter.
410 */
df869b63 411struct timeval ns_to_timeval(const s64 nsec)
f8f46da3
TG
412{
413 struct timespec ts = ns_to_timespec(nsec);
414 struct timeval tv;
415
416 tv.tv_sec = ts.tv_sec;
417 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
418
419 return tv;
420}
b7aa0bf7 421EXPORT_SYMBOL(ns_to_timeval);
f8f46da3 422
41cf5445
IM
423/*
424 * When we convert to jiffies then we interpret incoming values
425 * the following way:
426 *
427 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
428 *
429 * - 'too large' values [that would result in larger than
430 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
431 *
432 * - all other values are converted to jiffies by either multiplying
433 * the input value by a factor or dividing it with a factor
434 *
435 * We must also be careful about 32-bit overflows.
436 */
8b9365d7
IM
437unsigned long msecs_to_jiffies(const unsigned int m)
438{
41cf5445
IM
439 /*
440 * Negative value, means infinite timeout:
441 */
442 if ((int)m < 0)
8b9365d7 443 return MAX_JIFFY_OFFSET;
41cf5445 444
8b9365d7 445#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
41cf5445
IM
446 /*
447 * HZ is equal to or smaller than 1000, and 1000 is a nice
448 * round multiple of HZ, divide with the factor between them,
449 * but round upwards:
450 */
8b9365d7
IM
451 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
452#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
41cf5445
IM
453 /*
454 * HZ is larger than 1000, and HZ is a nice round multiple of
455 * 1000 - simply multiply with the factor between them.
456 *
457 * But first make sure the multiplication result cannot
458 * overflow:
459 */
460 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
461 return MAX_JIFFY_OFFSET;
462
8b9365d7
IM
463 return m * (HZ / MSEC_PER_SEC);
464#else
41cf5445
IM
465 /*
466 * Generic case - multiply, round and divide. But first
467 * check that if we are doing a net multiplication, that
bdc80787 468 * we wouldn't overflow:
41cf5445
IM
469 */
470 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
471 return MAX_JIFFY_OFFSET;
472
b9095fd8 473 return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
bdc80787 474 >> MSEC_TO_HZ_SHR32;
8b9365d7
IM
475#endif
476}
477EXPORT_SYMBOL(msecs_to_jiffies);
478
479unsigned long usecs_to_jiffies(const unsigned int u)
480{
481 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
482 return MAX_JIFFY_OFFSET;
483#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
484 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
485#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
486 return u * (HZ / USEC_PER_SEC);
487#else
b9095fd8 488 return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
bdc80787 489 >> USEC_TO_HZ_SHR32;
8b9365d7
IM
490#endif
491}
492EXPORT_SYMBOL(usecs_to_jiffies);
493
494/*
495 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
496 * that a remainder subtract here would not do the right thing as the
497 * resolution values don't fall on second boundries. I.e. the line:
498 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
499 *
500 * Rather, we just shift the bits off the right.
501 *
502 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
503 * value to a scaled second value.
504 */
505unsigned long
506timespec_to_jiffies(const struct timespec *value)
507{
508 unsigned long sec = value->tv_sec;
509 long nsec = value->tv_nsec + TICK_NSEC - 1;
510
511 if (sec >= MAX_SEC_IN_JIFFIES){
512 sec = MAX_SEC_IN_JIFFIES;
513 nsec = 0;
514 }
515 return (((u64)sec * SEC_CONVERSION) +
516 (((u64)nsec * NSEC_CONVERSION) >>
517 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
518
519}
520EXPORT_SYMBOL(timespec_to_jiffies);
521
522void
523jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
524{
525 /*
526 * Convert jiffies to nanoseconds and separate with
527 * one divide.
528 */
f8bd2258
RZ
529 u32 rem;
530 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
531 NSEC_PER_SEC, &rem);
532 value->tv_nsec = rem;
8b9365d7
IM
533}
534EXPORT_SYMBOL(jiffies_to_timespec);
535
536/* Same for "timeval"
537 *
538 * Well, almost. The problem here is that the real system resolution is
539 * in nanoseconds and the value being converted is in micro seconds.
540 * Also for some machines (those that use HZ = 1024, in-particular),
541 * there is a LARGE error in the tick size in microseconds.
542
543 * The solution we use is to do the rounding AFTER we convert the
544 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
545 * Instruction wise, this should cost only an additional add with carry
546 * instruction above the way it was done above.
547 */
548unsigned long
549timeval_to_jiffies(const struct timeval *value)
550{
551 unsigned long sec = value->tv_sec;
552 long usec = value->tv_usec;
553
554 if (sec >= MAX_SEC_IN_JIFFIES){
555 sec = MAX_SEC_IN_JIFFIES;
556 usec = 0;
557 }
558 return (((u64)sec * SEC_CONVERSION) +
559 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
560 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
561}
456a09dc 562EXPORT_SYMBOL(timeval_to_jiffies);
8b9365d7
IM
563
564void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
565{
566 /*
567 * Convert jiffies to nanoseconds and separate with
568 * one divide.
569 */
f8bd2258 570 u32 rem;
8b9365d7 571
f8bd2258
RZ
572 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
573 NSEC_PER_SEC, &rem);
574 value->tv_usec = rem / NSEC_PER_USEC;
8b9365d7 575}
456a09dc 576EXPORT_SYMBOL(jiffies_to_timeval);
8b9365d7
IM
577
578/*
579 * Convert jiffies/jiffies_64 to clock_t and back.
580 */
cbbc719f 581clock_t jiffies_to_clock_t(unsigned long x)
8b9365d7
IM
582{
583#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
6ffc787a
DF
584# if HZ < USER_HZ
585 return x * (USER_HZ / HZ);
586# else
8b9365d7 587 return x / (HZ / USER_HZ);
6ffc787a 588# endif
8b9365d7 589#else
71abb3af 590 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
8b9365d7
IM
591#endif
592}
593EXPORT_SYMBOL(jiffies_to_clock_t);
594
595unsigned long clock_t_to_jiffies(unsigned long x)
596{
597#if (HZ % USER_HZ)==0
598 if (x >= ~0UL / (HZ / USER_HZ))
599 return ~0UL;
600 return x * (HZ / USER_HZ);
601#else
8b9365d7
IM
602 /* Don't worry about loss of precision here .. */
603 if (x >= ~0UL / HZ * USER_HZ)
604 return ~0UL;
605
606 /* .. but do try to contain it here */
71abb3af 607 return div_u64((u64)x * HZ, USER_HZ);
8b9365d7
IM
608#endif
609}
610EXPORT_SYMBOL(clock_t_to_jiffies);
611
612u64 jiffies_64_to_clock_t(u64 x)
613{
614#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
6ffc787a 615# if HZ < USER_HZ
71abb3af 616 x = div_u64(x * USER_HZ, HZ);
ec03d707 617# elif HZ > USER_HZ
71abb3af 618 x = div_u64(x, HZ / USER_HZ);
ec03d707
AM
619# else
620 /* Nothing to do */
6ffc787a 621# endif
8b9365d7
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622#else
623 /*
624 * There are better ways that don't overflow early,
625 * but even this doesn't overflow in hundreds of years
626 * in 64 bits, so..
627 */
71abb3af 628 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
8b9365d7
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629#endif
630 return x;
631}
8b9365d7
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632EXPORT_SYMBOL(jiffies_64_to_clock_t);
633
634u64 nsec_to_clock_t(u64 x)
635{
636#if (NSEC_PER_SEC % USER_HZ) == 0
71abb3af 637 return div_u64(x, NSEC_PER_SEC / USER_HZ);
8b9365d7 638#elif (USER_HZ % 512) == 0
71abb3af 639 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
8b9365d7
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640#else
641 /*
642 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
643 * overflow after 64.99 years.
644 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
645 */
71abb3af 646 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
8b9365d7 647#endif
8b9365d7
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648}
649
b7b20df9 650/**
a1dabb6b 651 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
b7b20df9
HS
652 *
653 * @n: nsecs in u64
654 *
655 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
656 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
657 * for scheduler, not for use in device drivers to calculate timeout value.
658 *
659 * note:
660 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
661 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
662 */
a1dabb6b 663u64 nsecs_to_jiffies64(u64 n)
b7b20df9
HS
664{
665#if (NSEC_PER_SEC % HZ) == 0
666 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
667 return div_u64(n, NSEC_PER_SEC / HZ);
668#elif (HZ % 512) == 0
669 /* overflow after 292 years if HZ = 1024 */
670 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
671#else
672 /*
673 * Generic case - optimized for cases where HZ is a multiple of 3.
674 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
675 */
676 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
677#endif
678}
679
a1dabb6b
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680/**
681 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
682 *
683 * @n: nsecs in u64
684 *
685 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
686 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
687 * for scheduler, not for use in device drivers to calculate timeout value.
688 *
689 * note:
690 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
691 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
692 */
693unsigned long nsecs_to_jiffies(u64 n)
694{
695 return (unsigned long)nsecs_to_jiffies64(n);
696}
697
df0cc053
TG
698/*
699 * Add two timespec values and do a safety check for overflow.
700 * It's assumed that both values are valid (>= 0)
701 */
702struct timespec timespec_add_safe(const struct timespec lhs,
703 const struct timespec rhs)
704{
705 struct timespec res;
706
707 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
708 lhs.tv_nsec + rhs.tv_nsec);
709
710 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
711 res.tv_sec = TIME_T_MAX;
712
713 return res;
714}