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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/export.h> |
31 | #include <linux/timex.h> |
32 | #include <linux/capability.h> |
33 | #include <linux/timekeeper_internal.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 | */ |
50 | struct timezone sys_tz; |
51 | |
52 | EXPORT_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 | */ |
62 | SYSCALL_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 | |
81 | SYSCALL_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 | |
101 | SYSCALL_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 | * Indicates if there is an offset between the system clock and the hardware |
119 | * clock/persistent clock/rtc. |
120 | */ |
121 | int persistent_clock_is_local; |
122 | |
123 | /* |
124 | * Adjust the time obtained from the CMOS to be UTC time instead of |
125 | * local time. |
126 | * |
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 |
129 | * confusion if the program gets run more than once; it would also be |
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 | * |
133 | * - TYT, 1992-01-01 |
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 | */ |
139 | static inline void warp_clock(void) |
140 | { |
141 | struct timespec adjust; |
142 | |
143 | adjust = current_kernel_time(); |
144 | if (sys_tz.tz_minuteswest != 0) |
145 | persistent_clock_is_local = 1; |
146 | adjust.tv_sec += sys_tz.tz_minuteswest * 60; |
147 | do_settimeofday(&adjust); |
148 | } |
149 | |
150 | /* |
151 | * In case for some reason the CMOS clock has not already been running |
152 | * in UTC, but in some local time: The first time we set the timezone, |
153 | * we will warp the clock so that it is ticking UTC time instead of |
154 | * local time. Presumably, if someone is setting the timezone then we |
155 | * are running in an environment where the programs understand about |
156 | * timezones. This should be done at boot time in the /etc/rc script, |
157 | * as soon as possible, so that the clock can be set right. Otherwise, |
158 | * various programs will get confused when the clock gets warped. |
159 | */ |
160 | |
161 | int do_sys_settimeofday(const struct timespec *tv, const struct timezone *tz) |
162 | { |
163 | static int firsttime = 1; |
164 | int error = 0; |
165 | |
166 | if (tv && !timespec_valid(tv)) |
167 | return -EINVAL; |
168 | |
169 | error = security_settime(tv, tz); |
170 | if (error) |
171 | return error; |
172 | |
173 | if (tz) { |
174 | sys_tz = *tz; |
175 | update_vsyscall_tz(); |
176 | if (firsttime) { |
177 | firsttime = 0; |
178 | if (!tv) |
179 | warp_clock(); |
180 | } |
181 | } |
182 | if (tv) |
183 | return do_settimeofday(tv); |
184 | return 0; |
185 | } |
186 | |
187 | SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv, |
188 | struct timezone __user *, tz) |
189 | { |
190 | struct timeval user_tv; |
191 | struct timespec new_ts; |
192 | struct timezone new_tz; |
193 | |
194 | if (tv) { |
195 | if (copy_from_user(&user_tv, tv, sizeof(*tv))) |
196 | return -EFAULT; |
197 | new_ts.tv_sec = user_tv.tv_sec; |
198 | new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC; |
199 | } |
200 | if (tz) { |
201 | if (copy_from_user(&new_tz, tz, sizeof(*tz))) |
202 | return -EFAULT; |
203 | } |
204 | |
205 | return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL); |
206 | } |
207 | |
208 | SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p) |
209 | { |
210 | struct timex txc; /* Local copy of parameter */ |
211 | int ret; |
212 | |
213 | /* Copy the user data space into the kernel copy |
214 | * structure. But bear in mind that the structures |
215 | * may change |
216 | */ |
217 | if(copy_from_user(&txc, txc_p, sizeof(struct timex))) |
218 | return -EFAULT; |
219 | ret = do_adjtimex(&txc); |
220 | return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret; |
221 | } |
222 | |
223 | /** |
224 | * current_fs_time - Return FS time |
225 | * @sb: Superblock. |
226 | * |
227 | * Return the current time truncated to the time granularity supported by |
228 | * the fs. |
229 | */ |
230 | struct timespec current_fs_time(struct super_block *sb) |
231 | { |
232 | struct timespec now = current_kernel_time(); |
233 | return timespec_trunc(now, sb->s_time_gran); |
234 | } |
235 | EXPORT_SYMBOL(current_fs_time); |
236 | |
237 | /* |
238 | * Convert jiffies to milliseconds and back. |
239 | * |
240 | * Avoid unnecessary multiplications/divisions in the |
241 | * two most common HZ cases: |
242 | */ |
243 | unsigned int jiffies_to_msecs(const unsigned long j) |
244 | { |
245 | #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) |
246 | return (MSEC_PER_SEC / HZ) * j; |
247 | #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) |
248 | return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC); |
249 | #else |
250 | # if BITS_PER_LONG == 32 |
251 | return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32; |
252 | # else |
253 | return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN; |
254 | # endif |
255 | #endif |
256 | } |
257 | EXPORT_SYMBOL(jiffies_to_msecs); |
258 | |
259 | unsigned int jiffies_to_usecs(const unsigned long j) |
260 | { |
261 | #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ) |
262 | return (USEC_PER_SEC / HZ) * j; |
263 | #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC) |
264 | return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC); |
265 | #else |
266 | # if BITS_PER_LONG == 32 |
267 | return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32; |
268 | # else |
269 | return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN; |
270 | # endif |
271 | #endif |
272 | } |
273 | EXPORT_SYMBOL(jiffies_to_usecs); |
274 | |
275 | /** |
276 | * timespec_trunc - Truncate timespec to a granularity |
277 | * @t: Timespec |
278 | * @gran: Granularity in ns. |
279 | * |
280 | * Truncate a timespec to a granularity. gran must be smaller than a second. |
281 | * Always rounds down. |
282 | * |
283 | * This function should be only used for timestamps returned by |
284 | * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because |
285 | * it doesn't handle the better resolution of the latter. |
286 | */ |
287 | struct timespec timespec_trunc(struct timespec t, unsigned gran) |
288 | { |
289 | /* |
290 | * Division is pretty slow so avoid it for common cases. |
291 | * Currently current_kernel_time() never returns better than |
292 | * jiffies resolution. Exploit that. |
293 | */ |
294 | if (gran <= jiffies_to_usecs(1) * 1000) { |
295 | /* nothing */ |
296 | } else if (gran == 1000000000) { |
297 | t.tv_nsec = 0; |
298 | } else { |
299 | t.tv_nsec -= t.tv_nsec % gran; |
300 | } |
301 | return t; |
302 | } |
303 | EXPORT_SYMBOL(timespec_trunc); |
304 | |
305 | /* Converts Gregorian date to seconds since 1970-01-01 00:00:00. |
306 | * Assumes input in normal date format, i.e. 1980-12-31 23:59:59 |
307 | * => year=1980, mon=12, day=31, hour=23, min=59, sec=59. |
308 | * |
309 | * [For the Julian calendar (which was used in Russia before 1917, |
310 | * Britain & colonies before 1752, anywhere else before 1582, |
311 | * and is still in use by some communities) leave out the |
312 | * -year/100+year/400 terms, and add 10.] |
313 | * |
314 | * This algorithm was first published by Gauss (I think). |
315 | * |
316 | * WARNING: this function will overflow on 2106-02-07 06:28:16 on |
317 | * machines where long is 32-bit! (However, as time_t is signed, we |
318 | * will already get problems at other places on 2038-01-19 03:14:08) |
319 | */ |
320 | unsigned long |
321 | mktime(const unsigned int year0, const unsigned int mon0, |
322 | const unsigned int day, const unsigned int hour, |
323 | const unsigned int min, const unsigned int sec) |
324 | { |
325 | unsigned int mon = mon0, year = year0; |
326 | |
327 | /* 1..12 -> 11,12,1..10 */ |
328 | if (0 >= (int) (mon -= 2)) { |
329 | mon += 12; /* Puts Feb last since it has leap day */ |
330 | year -= 1; |
331 | } |
332 | |
333 | return ((((unsigned long) |
334 | (year/4 - year/100 + year/400 + 367*mon/12 + day) + |
335 | year*365 - 719499 |
336 | )*24 + hour /* now have hours */ |
337 | )*60 + min /* now have minutes */ |
338 | )*60 + sec; /* finally seconds */ |
339 | } |
340 | |
341 | EXPORT_SYMBOL(mktime); |
342 | |
343 | /** |
344 | * set_normalized_timespec - set timespec sec and nsec parts and normalize |
345 | * |
346 | * @ts: pointer to timespec variable to be set |
347 | * @sec: seconds to set |
348 | * @nsec: nanoseconds to set |
349 | * |
350 | * Set seconds and nanoseconds field of a timespec variable and |
351 | * normalize to the timespec storage format |
352 | * |
353 | * Note: The tv_nsec part is always in the range of |
354 | * 0 <= tv_nsec < NSEC_PER_SEC |
355 | * For negative values only the tv_sec field is negative ! |
356 | */ |
357 | void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec) |
358 | { |
359 | while (nsec >= NSEC_PER_SEC) { |
360 | /* |
361 | * The following asm() prevents the compiler from |
362 | * optimising this loop into a modulo operation. See |
363 | * also __iter_div_u64_rem() in include/linux/time.h |
364 | */ |
365 | asm("" : "+rm"(nsec)); |
366 | nsec -= NSEC_PER_SEC; |
367 | ++sec; |
368 | } |
369 | while (nsec < 0) { |
370 | asm("" : "+rm"(nsec)); |
371 | nsec += NSEC_PER_SEC; |
372 | --sec; |
373 | } |
374 | ts->tv_sec = sec; |
375 | ts->tv_nsec = nsec; |
376 | } |
377 | EXPORT_SYMBOL(set_normalized_timespec); |
378 | |
379 | /** |
380 | * ns_to_timespec - Convert nanoseconds to timespec |
381 | * @nsec: the nanoseconds value to be converted |
382 | * |
383 | * Returns the timespec representation of the nsec parameter. |
384 | */ |
385 | struct timespec ns_to_timespec(const s64 nsec) |
386 | { |
387 | struct timespec ts; |
388 | s32 rem; |
389 | |
390 | if (!nsec) |
391 | return (struct timespec) {0, 0}; |
392 | |
393 | ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem); |
394 | if (unlikely(rem < 0)) { |
395 | ts.tv_sec--; |
396 | rem += NSEC_PER_SEC; |
397 | } |
398 | ts.tv_nsec = rem; |
399 | |
400 | return ts; |
401 | } |
402 | EXPORT_SYMBOL(ns_to_timespec); |
403 | |
404 | /** |
405 | * ns_to_timeval - Convert nanoseconds to timeval |
406 | * @nsec: the nanoseconds value to be converted |
407 | * |
408 | * Returns the timeval representation of the nsec parameter. |
409 | */ |
410 | struct timeval ns_to_timeval(const s64 nsec) |
411 | { |
412 | struct timespec ts = ns_to_timespec(nsec); |
413 | struct timeval tv; |
414 | |
415 | tv.tv_sec = ts.tv_sec; |
416 | tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000; |
417 | |
418 | return tv; |
419 | } |
420 | EXPORT_SYMBOL(ns_to_timeval); |
421 | |
422 | /* |
423 | * When we convert to jiffies then we interpret incoming values |
424 | * the following way: |
425 | * |
426 | * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET) |
427 | * |
428 | * - 'too large' values [that would result in larger than |
429 | * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. |
430 | * |
431 | * - all other values are converted to jiffies by either multiplying |
432 | * the input value by a factor or dividing it with a factor |
433 | * |
434 | * We must also be careful about 32-bit overflows. |
435 | */ |
436 | unsigned long msecs_to_jiffies(const unsigned int m) |
437 | { |
438 | /* |
439 | * Negative value, means infinite timeout: |
440 | */ |
441 | if ((int)m < 0) |
442 | return MAX_JIFFY_OFFSET; |
443 | |
444 | #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) |
445 | /* |
446 | * HZ is equal to or smaller than 1000, and 1000 is a nice |
447 | * round multiple of HZ, divide with the factor between them, |
448 | * but round upwards: |
449 | */ |
450 | return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ); |
451 | #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) |
452 | /* |
453 | * HZ is larger than 1000, and HZ is a nice round multiple of |
454 | * 1000 - simply multiply with the factor between them. |
455 | * |
456 | * But first make sure the multiplication result cannot |
457 | * overflow: |
458 | */ |
459 | if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) |
460 | return MAX_JIFFY_OFFSET; |
461 | |
462 | return m * (HZ / MSEC_PER_SEC); |
463 | #else |
464 | /* |
465 | * Generic case - multiply, round and divide. But first |
466 | * check that if we are doing a net multiplication, that |
467 | * we wouldn't overflow: |
468 | */ |
469 | if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) |
470 | return MAX_JIFFY_OFFSET; |
471 | |
472 | return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) |
473 | >> MSEC_TO_HZ_SHR32; |
474 | #endif |
475 | } |
476 | EXPORT_SYMBOL(msecs_to_jiffies); |
477 | |
478 | unsigned long usecs_to_jiffies(const unsigned int u) |
479 | { |
480 | if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET)) |
481 | return MAX_JIFFY_OFFSET; |
482 | #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ) |
483 | return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ); |
484 | #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC) |
485 | return u * (HZ / USEC_PER_SEC); |
486 | #else |
487 | return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32) |
488 | >> USEC_TO_HZ_SHR32; |
489 | #endif |
490 | } |
491 | EXPORT_SYMBOL(usecs_to_jiffies); |
492 | |
493 | /* |
494 | * The TICK_NSEC - 1 rounds up the value to the next resolution. Note |
495 | * that a remainder subtract here would not do the right thing as the |
496 | * resolution values don't fall on second boundries. I.e. the line: |
497 | * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding. |
498 | * |
499 | * Rather, we just shift the bits off the right. |
500 | * |
501 | * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec |
502 | * value to a scaled second value. |
503 | */ |
504 | unsigned long |
505 | timespec_to_jiffies(const struct timespec *value) |
506 | { |
507 | unsigned long sec = value->tv_sec; |
508 | long nsec = value->tv_nsec + TICK_NSEC - 1; |
509 | |
510 | if (sec >= MAX_SEC_IN_JIFFIES){ |
511 | sec = MAX_SEC_IN_JIFFIES; |
512 | nsec = 0; |
513 | } |
514 | return (((u64)sec * SEC_CONVERSION) + |
515 | (((u64)nsec * NSEC_CONVERSION) >> |
516 | (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC; |
517 | |
518 | } |
519 | EXPORT_SYMBOL(timespec_to_jiffies); |
520 | |
521 | void |
522 | jiffies_to_timespec(const unsigned long jiffies, struct timespec *value) |
523 | { |
524 | /* |
525 | * Convert jiffies to nanoseconds and separate with |
526 | * one divide. |
527 | */ |
528 | u32 rem; |
529 | value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, |
530 | NSEC_PER_SEC, &rem); |
531 | value->tv_nsec = rem; |
532 | } |
533 | EXPORT_SYMBOL(jiffies_to_timespec); |
534 | |
535 | /* Same for "timeval" |
536 | * |
537 | * Well, almost. The problem here is that the real system resolution is |
538 | * in nanoseconds and the value being converted is in micro seconds. |
539 | * Also for some machines (those that use HZ = 1024, in-particular), |
540 | * there is a LARGE error in the tick size in microseconds. |
541 | |
542 | * The solution we use is to do the rounding AFTER we convert the |
543 | * microsecond part. Thus the USEC_ROUND, the bits to be shifted off. |
544 | * Instruction wise, this should cost only an additional add with carry |
545 | * instruction above the way it was done above. |
546 | */ |
547 | unsigned long |
548 | timeval_to_jiffies(const struct timeval *value) |
549 | { |
550 | unsigned long sec = value->tv_sec; |
551 | long usec = value->tv_usec; |
552 | |
553 | if (sec >= MAX_SEC_IN_JIFFIES){ |
554 | sec = MAX_SEC_IN_JIFFIES; |
555 | usec = 0; |
556 | } |
557 | return (((u64)sec * SEC_CONVERSION) + |
558 | (((u64)usec * USEC_CONVERSION + USEC_ROUND) >> |
559 | (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC; |
560 | } |
561 | EXPORT_SYMBOL(timeval_to_jiffies); |
562 | |
563 | void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value) |
564 | { |
565 | /* |
566 | * Convert jiffies to nanoseconds and separate with |
567 | * one divide. |
568 | */ |
569 | u32 rem; |
570 | |
571 | value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, |
572 | NSEC_PER_SEC, &rem); |
573 | value->tv_usec = rem / NSEC_PER_USEC; |
574 | } |
575 | EXPORT_SYMBOL(jiffies_to_timeval); |
576 | |
577 | /* |
578 | * Convert jiffies/jiffies_64 to clock_t and back. |
579 | */ |
580 | clock_t jiffies_to_clock_t(unsigned long x) |
581 | { |
582 | #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 |
583 | # if HZ < USER_HZ |
584 | return x * (USER_HZ / HZ); |
585 | # else |
586 | return x / (HZ / USER_HZ); |
587 | # endif |
588 | #else |
589 | return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ); |
590 | #endif |
591 | } |
592 | EXPORT_SYMBOL(jiffies_to_clock_t); |
593 | |
594 | unsigned long clock_t_to_jiffies(unsigned long x) |
595 | { |
596 | #if (HZ % USER_HZ)==0 |
597 | if (x >= ~0UL / (HZ / USER_HZ)) |
598 | return ~0UL; |
599 | return x * (HZ / USER_HZ); |
600 | #else |
601 | /* Don't worry about loss of precision here .. */ |
602 | if (x >= ~0UL / HZ * USER_HZ) |
603 | return ~0UL; |
604 | |
605 | /* .. but do try to contain it here */ |
606 | return div_u64((u64)x * HZ, USER_HZ); |
607 | #endif |
608 | } |
609 | EXPORT_SYMBOL(clock_t_to_jiffies); |
610 | |
611 | u64 jiffies_64_to_clock_t(u64 x) |
612 | { |
613 | #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 |
614 | # if HZ < USER_HZ |
615 | x = div_u64(x * USER_HZ, HZ); |
616 | # elif HZ > USER_HZ |
617 | x = div_u64(x, HZ / USER_HZ); |
618 | # else |
619 | /* Nothing to do */ |
620 | # endif |
621 | #else |
622 | /* |
623 | * There are better ways that don't overflow early, |
624 | * but even this doesn't overflow in hundreds of years |
625 | * in 64 bits, so.. |
626 | */ |
627 | x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ)); |
628 | #endif |
629 | return x; |
630 | } |
631 | EXPORT_SYMBOL(jiffies_64_to_clock_t); |
632 | |
633 | u64 nsec_to_clock_t(u64 x) |
634 | { |
635 | #if (NSEC_PER_SEC % USER_HZ) == 0 |
636 | return div_u64(x, NSEC_PER_SEC / USER_HZ); |
637 | #elif (USER_HZ % 512) == 0 |
638 | return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512); |
639 | #else |
640 | /* |
641 | * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024, |
642 | * overflow after 64.99 years. |
643 | * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ... |
644 | */ |
645 | return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ); |
646 | #endif |
647 | } |
648 | |
649 | /** |
650 | * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64 |
651 | * |
652 | * @n: nsecs in u64 |
653 | * |
654 | * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. |
655 | * And this doesn't return MAX_JIFFY_OFFSET since this function is designed |
656 | * for scheduler, not for use in device drivers to calculate timeout value. |
657 | * |
658 | * note: |
659 | * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) |
660 | * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years |
661 | */ |
662 | u64 nsecs_to_jiffies64(u64 n) |
663 | { |
664 | #if (NSEC_PER_SEC % HZ) == 0 |
665 | /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */ |
666 | return div_u64(n, NSEC_PER_SEC / HZ); |
667 | #elif (HZ % 512) == 0 |
668 | /* overflow after 292 years if HZ = 1024 */ |
669 | return div_u64(n * HZ / 512, NSEC_PER_SEC / 512); |
670 | #else |
671 | /* |
672 | * Generic case - optimized for cases where HZ is a multiple of 3. |
673 | * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc. |
674 | */ |
675 | return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ); |
676 | #endif |
677 | } |
678 | |
679 | /** |
680 | * nsecs_to_jiffies - Convert nsecs in u64 to jiffies |
681 | * |
682 | * @n: nsecs in u64 |
683 | * |
684 | * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. |
685 | * And this doesn't return MAX_JIFFY_OFFSET since this function is designed |
686 | * for scheduler, not for use in device drivers to calculate timeout value. |
687 | * |
688 | * note: |
689 | * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) |
690 | * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years |
691 | */ |
692 | unsigned long nsecs_to_jiffies(u64 n) |
693 | { |
694 | return (unsigned long)nsecs_to_jiffies64(n); |
695 | } |
696 | |
697 | /* |
698 | * Add two timespec values and do a safety check for overflow. |
699 | * It's assumed that both values are valid (>= 0) |
700 | */ |
701 | struct timespec timespec_add_safe(const struct timespec lhs, |
702 | const struct timespec rhs) |
703 | { |
704 | struct timespec res; |
705 | |
706 | set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec, |
707 | lhs.tv_nsec + rhs.tv_nsec); |
708 | |
709 | if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec) |
710 | res.tv_sec = TIME_T_MAX; |
711 | |
712 | return res; |
713 | } |
714 |
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v2.6.34-rc5
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