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/core.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 <generated/timeconst.h> 45 #include "timekeeping.h" 46 47 /* 48 * The timezone where the local system is located. Used as a default by some 49 * programs who obtain this value by using gettimeofday. 50 */ 51 struct timezone sys_tz; 52 53 EXPORT_SYMBOL(sys_tz); 54 55 #ifdef __ARCH_WANT_SYS_TIME 56 57 /* 58 * sys_time() can be implemented in user-level using 59 * sys_gettimeofday(). Is this for backwards compatibility? If so, 60 * why not move it into the appropriate arch directory (for those 61 * architectures that need it). 62 */ 63 SYSCALL_DEFINE1(time, time_t __user *, tloc) 64 { 65 time_t i = get_seconds(); 66 67 if (tloc) { 68 if (put_user(i,tloc)) 69 return -EFAULT; 70 } 71 force_successful_syscall_return(); 72 return i; 73 } 74 75 /* 76 * sys_stime() can be implemented in user-level using 77 * sys_settimeofday(). Is this for backwards compatibility? If so, 78 * why not move it into the appropriate arch directory (for those 79 * architectures that need it). 80 */ 81 82 SYSCALL_DEFINE1(stime, time_t __user *, tptr) 83 { 84 struct timespec tv; 85 int err; 86 87 if (get_user(tv.tv_sec, tptr)) 88 return -EFAULT; 89 90 tv.tv_nsec = 0; 91 92 err = security_settime(&tv, NULL); 93 if (err) 94 return err; 95 96 do_settimeofday(&tv); 97 return 0; 98 } 99 100 #endif /* __ARCH_WANT_SYS_TIME */ 101 102 SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv, 103 struct timezone __user *, tz) 104 { 105 if (likely(tv != NULL)) { 106 struct timeval ktv; 107 do_gettimeofday(&ktv); 108 if (copy_to_user(tv, &ktv, sizeof(ktv))) 109 return -EFAULT; 110 } 111 if (unlikely(tz != NULL)) { 112 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz))) 113 return -EFAULT; 114 } 115 return 0; 116 } 117 118 /* 119 * Indicates if there is an offset between the system clock and the hardware 120 * clock/persistent clock/rtc. 121 */ 122 int persistent_clock_is_local; 123 124 /* 125 * Adjust the time obtained from the CMOS to be UTC time instead of 126 * local time. 127 * 128 * This is ugly, but preferable to the alternatives. Otherwise we 129 * would either need to write a program to do it in /etc/rc (and risk 130 * confusion if the program gets run more than once; it would also be 131 * hard to make the program warp the clock precisely n hours) or 132 * compile in the timezone information into the kernel. Bad, bad.... 133 * 134 * - TYT, 1992-01-01 135 * 136 * The best thing to do is to keep the CMOS clock in universal time (UTC) 137 * as real UNIX machines always do it. This avoids all headaches about 138 * daylight saving times and warping kernel clocks. 139 */ 140 static inline void warp_clock(void) 141 { 142 if (sys_tz.tz_minuteswest != 0) { 143 struct timespec adjust; 144 145 persistent_clock_is_local = 1; 146 adjust.tv_sec = sys_tz.tz_minuteswest * 60; 147 adjust.tv_nsec = 0; 148 timekeeping_inject_offset(&adjust); 149 } 150 } 151 152 /* 153 * In case for some reason the CMOS clock has not already been running 154 * in UTC, but in some local time: The first time we set the timezone, 155 * we will warp the clock so that it is ticking UTC time instead of 156 * local time. Presumably, if someone is setting the timezone then we 157 * are running in an environment where the programs understand about 158 * timezones. This should be done at boot time in the /etc/rc script, 159 * as soon as possible, so that the clock can be set right. Otherwise, 160 * various programs will get confused when the clock gets warped. 161 */ 162 163 int do_sys_settimeofday(const struct timespec *tv, const struct timezone *tz) 164 { 165 static int firsttime = 1; 166 int error = 0; 167 168 if (tv && !timespec_valid(tv)) 169 return -EINVAL; 170 171 error = security_settime(tv, tz); 172 if (error) 173 return error; 174 175 if (tz) { 176 /* Verify we're witin the +-15 hrs range */ 177 if (tz->tz_minuteswest > 15*60 || tz->tz_minuteswest < -15*60) 178 return -EINVAL; 179 180 sys_tz = *tz; 181 update_vsyscall_tz(); 182 if (firsttime) { 183 firsttime = 0; 184 if (!tv) 185 warp_clock(); 186 } 187 } 188 if (tv) 189 return do_settimeofday(tv); 190 return 0; 191 } 192 193 SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv, 194 struct timezone __user *, tz) 195 { 196 struct timeval user_tv; 197 struct timespec new_ts; 198 struct timezone new_tz; 199 200 if (tv) { 201 if (copy_from_user(&user_tv, tv, sizeof(*tv))) 202 return -EFAULT; 203 204 if (!timeval_valid(&user_tv)) 205 return -EINVAL; 206 207 new_ts.tv_sec = user_tv.tv_sec; 208 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC; 209 } 210 if (tz) { 211 if (copy_from_user(&new_tz, tz, sizeof(*tz))) 212 return -EFAULT; 213 } 214 215 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL); 216 } 217 218 SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p) 219 { 220 struct timex txc; /* Local copy of parameter */ 221 int ret; 222 223 /* Copy the user data space into the kernel copy 224 * structure. But bear in mind that the structures 225 * may change 226 */ 227 if(copy_from_user(&txc, txc_p, sizeof(struct timex))) 228 return -EFAULT; 229 ret = do_adjtimex(&txc); 230 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret; 231 } 232 233 /** 234 * current_fs_time - Return FS time 235 * @sb: Superblock. 236 * 237 * Return the current time truncated to the time granularity supported by 238 * the fs. 239 */ 240 struct timespec current_fs_time(struct super_block *sb) 241 { 242 struct timespec now = current_kernel_time(); 243 return timespec_trunc(now, sb->s_time_gran); 244 } 245 EXPORT_SYMBOL(current_fs_time); 246 247 /* 248 * Convert jiffies to milliseconds and back. 249 * 250 * Avoid unnecessary multiplications/divisions in the 251 * two most common HZ cases: 252 */ 253 unsigned int jiffies_to_msecs(const unsigned long j) 254 { 255 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) 256 return (MSEC_PER_SEC / HZ) * j; 257 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) 258 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC); 259 #else 260 # if BITS_PER_LONG == 32 261 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32; 262 # else 263 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN; 264 # endif 265 #endif 266 } 267 EXPORT_SYMBOL(jiffies_to_msecs); 268 269 unsigned int jiffies_to_usecs(const unsigned long j) 270 { 271 /* 272 * Hz usually doesn't go much further MSEC_PER_SEC. 273 * jiffies_to_usecs() and usecs_to_jiffies() depend on that. 274 */ 275 BUILD_BUG_ON(HZ > USEC_PER_SEC); 276 277 #if !(USEC_PER_SEC % HZ) 278 return (USEC_PER_SEC / HZ) * j; 279 #else 280 # if BITS_PER_LONG == 32 281 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32; 282 # else 283 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN; 284 # endif 285 #endif 286 } 287 EXPORT_SYMBOL(jiffies_to_usecs); 288 289 /** 290 * timespec_trunc - Truncate timespec to a granularity 291 * @t: Timespec 292 * @gran: Granularity in ns. 293 * 294 * Truncate a timespec to a granularity. Always rounds down. gran must 295 * not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns). 296 */ 297 struct timespec timespec_trunc(struct timespec t, unsigned gran) 298 { 299 /* Avoid division in the common cases 1 ns and 1 s. */ 300 if (gran == 1) { 301 /* nothing */ 302 } else if (gran == NSEC_PER_SEC) { 303 t.tv_nsec = 0; 304 } else if (gran > 1 && gran < NSEC_PER_SEC) { 305 t.tv_nsec -= t.tv_nsec % gran; 306 } else { 307 WARN(1, "illegal file time granularity: %u", gran); 308 } 309 return t; 310 } 311 EXPORT_SYMBOL(timespec_trunc); 312 313 /* 314 * mktime64 - Converts date to seconds. 315 * Converts Gregorian date to seconds since 1970-01-01 00:00:00. 316 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59 317 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59. 318 * 319 * [For the Julian calendar (which was used in Russia before 1917, 320 * Britain & colonies before 1752, anywhere else before 1582, 321 * and is still in use by some communities) leave out the 322 * -year/100+year/400 terms, and add 10.] 323 * 324 * This algorithm was first published by Gauss (I think). 325 */ 326 time64_t mktime64(const unsigned int year0, const unsigned int mon0, 327 const unsigned int day, const unsigned int hour, 328 const unsigned int min, const unsigned int sec) 329 { 330 unsigned int mon = mon0, year = year0; 331 332 /* 1..12 -> 11,12,1..10 */ 333 if (0 >= (int) (mon -= 2)) { 334 mon += 12; /* Puts Feb last since it has leap day */ 335 year -= 1; 336 } 337 338 return ((((time64_t) 339 (year/4 - year/100 + year/400 + 367*mon/12 + day) + 340 year*365 - 719499 341 )*24 + hour /* now have hours */ 342 )*60 + min /* now have minutes */ 343 )*60 + sec; /* finally seconds */ 344 } 345 EXPORT_SYMBOL(mktime64); 346 347 /** 348 * set_normalized_timespec - set timespec sec and nsec parts and normalize 349 * 350 * @ts: pointer to timespec variable to be set 351 * @sec: seconds to set 352 * @nsec: nanoseconds to set 353 * 354 * Set seconds and nanoseconds field of a timespec variable and 355 * normalize to the timespec storage format 356 * 357 * Note: The tv_nsec part is always in the range of 358 * 0 <= tv_nsec < NSEC_PER_SEC 359 * For negative values only the tv_sec field is negative ! 360 */ 361 void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec) 362 { 363 while (nsec >= NSEC_PER_SEC) { 364 /* 365 * The following asm() prevents the compiler from 366 * optimising this loop into a modulo operation. See 367 * also __iter_div_u64_rem() in include/linux/time.h 368 */ 369 asm("" : "+rm"(nsec)); 370 nsec -= NSEC_PER_SEC; 371 ++sec; 372 } 373 while (nsec < 0) { 374 asm("" : "+rm"(nsec)); 375 nsec += NSEC_PER_SEC; 376 --sec; 377 } 378 ts->tv_sec = sec; 379 ts->tv_nsec = nsec; 380 } 381 EXPORT_SYMBOL(set_normalized_timespec); 382 383 /** 384 * ns_to_timespec - Convert nanoseconds to timespec 385 * @nsec: the nanoseconds value to be converted 386 * 387 * Returns the timespec representation of the nsec parameter. 388 */ 389 struct timespec ns_to_timespec(const s64 nsec) 390 { 391 struct timespec ts; 392 s32 rem; 393 394 if (!nsec) 395 return (struct timespec) {0, 0}; 396 397 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem); 398 if (unlikely(rem < 0)) { 399 ts.tv_sec--; 400 rem += NSEC_PER_SEC; 401 } 402 ts.tv_nsec = rem; 403 404 return ts; 405 } 406 EXPORT_SYMBOL(ns_to_timespec); 407 408 /** 409 * ns_to_timeval - Convert nanoseconds to timeval 410 * @nsec: the nanoseconds value to be converted 411 * 412 * Returns the timeval representation of the nsec parameter. 413 */ 414 struct timeval ns_to_timeval(const s64 nsec) 415 { 416 struct timespec ts = ns_to_timespec(nsec); 417 struct timeval tv; 418 419 tv.tv_sec = ts.tv_sec; 420 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000; 421 422 return tv; 423 } 424 EXPORT_SYMBOL(ns_to_timeval); 425 426 #if BITS_PER_LONG == 32 427 /** 428 * set_normalized_timespec - set timespec sec and nsec parts and normalize 429 * 430 * @ts: pointer to timespec variable to be set 431 * @sec: seconds to set 432 * @nsec: nanoseconds to set 433 * 434 * Set seconds and nanoseconds field of a timespec variable and 435 * normalize to the timespec storage format 436 * 437 * Note: The tv_nsec part is always in the range of 438 * 0 <= tv_nsec < NSEC_PER_SEC 439 * For negative values only the tv_sec field is negative ! 440 */ 441 void set_normalized_timespec64(struct timespec64 *ts, time64_t sec, s64 nsec) 442 { 443 while (nsec >= NSEC_PER_SEC) { 444 /* 445 * The following asm() prevents the compiler from 446 * optimising this loop into a modulo operation. See 447 * also __iter_div_u64_rem() in include/linux/time.h 448 */ 449 asm("" : "+rm"(nsec)); 450 nsec -= NSEC_PER_SEC; 451 ++sec; 452 } 453 while (nsec < 0) { 454 asm("" : "+rm"(nsec)); 455 nsec += NSEC_PER_SEC; 456 --sec; 457 } 458 ts->tv_sec = sec; 459 ts->tv_nsec = nsec; 460 } 461 EXPORT_SYMBOL(set_normalized_timespec64); 462 463 /** 464 * ns_to_timespec64 - Convert nanoseconds to timespec64 465 * @nsec: the nanoseconds value to be converted 466 * 467 * Returns the timespec64 representation of the nsec parameter. 468 */ 469 struct timespec64 ns_to_timespec64(const s64 nsec) 470 { 471 struct timespec64 ts; 472 s32 rem; 473 474 if (!nsec) 475 return (struct timespec64) {0, 0}; 476 477 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem); 478 if (unlikely(rem < 0)) { 479 ts.tv_sec--; 480 rem += NSEC_PER_SEC; 481 } 482 ts.tv_nsec = rem; 483 484 return ts; 485 } 486 EXPORT_SYMBOL(ns_to_timespec64); 487 #endif 488 /** 489 * msecs_to_jiffies: - convert milliseconds to jiffies 490 * @m: time in milliseconds 491 * 492 * conversion is done as follows: 493 * 494 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET) 495 * 496 * - 'too large' values [that would result in larger than 497 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. 498 * 499 * - all other values are converted to jiffies by either multiplying 500 * the input value by a factor or dividing it with a factor and 501 * handling any 32-bit overflows. 502 * for the details see __msecs_to_jiffies() 503 * 504 * msecs_to_jiffies() checks for the passed in value being a constant 505 * via __builtin_constant_p() allowing gcc to eliminate most of the 506 * code, __msecs_to_jiffies() is called if the value passed does not 507 * allow constant folding and the actual conversion must be done at 508 * runtime. 509 * the _msecs_to_jiffies helpers are the HZ dependent conversion 510 * routines found in include/linux/jiffies.h 511 */ 512 unsigned long __msecs_to_jiffies(const unsigned int m) 513 { 514 /* 515 * Negative value, means infinite timeout: 516 */ 517 if ((int)m < 0) 518 return MAX_JIFFY_OFFSET; 519 return _msecs_to_jiffies(m); 520 } 521 EXPORT_SYMBOL(__msecs_to_jiffies); 522 523 unsigned long __usecs_to_jiffies(const unsigned int u) 524 { 525 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET)) 526 return MAX_JIFFY_OFFSET; 527 return _usecs_to_jiffies(u); 528 } 529 EXPORT_SYMBOL(__usecs_to_jiffies); 530 531 /* 532 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note 533 * that a remainder subtract here would not do the right thing as the 534 * resolution values don't fall on second boundries. I.e. the line: 535 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding. 536 * Note that due to the small error in the multiplier here, this 537 * rounding is incorrect for sufficiently large values of tv_nsec, but 538 * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're 539 * OK. 540 * 541 * Rather, we just shift the bits off the right. 542 * 543 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec 544 * value to a scaled second value. 545 */ 546 static unsigned long 547 __timespec64_to_jiffies(u64 sec, long nsec) 548 { 549 nsec = nsec + TICK_NSEC - 1; 550 551 if (sec >= MAX_SEC_IN_JIFFIES){ 552 sec = MAX_SEC_IN_JIFFIES; 553 nsec = 0; 554 } 555 return ((sec * SEC_CONVERSION) + 556 (((u64)nsec * NSEC_CONVERSION) >> 557 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC; 558 559 } 560 561 static unsigned long 562 __timespec_to_jiffies(unsigned long sec, long nsec) 563 { 564 return __timespec64_to_jiffies((u64)sec, nsec); 565 } 566 567 unsigned long 568 timespec64_to_jiffies(const struct timespec64 *value) 569 { 570 return __timespec64_to_jiffies(value->tv_sec, value->tv_nsec); 571 } 572 EXPORT_SYMBOL(timespec64_to_jiffies); 573 574 void 575 jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value) 576 { 577 /* 578 * Convert jiffies to nanoseconds and separate with 579 * one divide. 580 */ 581 u32 rem; 582 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, 583 NSEC_PER_SEC, &rem); 584 value->tv_nsec = rem; 585 } 586 EXPORT_SYMBOL(jiffies_to_timespec64); 587 588 /* 589 * We could use a similar algorithm to timespec_to_jiffies (with a 590 * different multiplier for usec instead of nsec). But this has a 591 * problem with rounding: we can't exactly add TICK_NSEC - 1 to the 592 * usec value, since it's not necessarily integral. 593 * 594 * We could instead round in the intermediate scaled representation 595 * (i.e. in units of 1/2^(large scale) jiffies) but that's also 596 * perilous: the scaling introduces a small positive error, which 597 * combined with a division-rounding-upward (i.e. adding 2^(scale) - 1 598 * units to the intermediate before shifting) leads to accidental 599 * overflow and overestimates. 600 * 601 * At the cost of one additional multiplication by a constant, just 602 * use the timespec implementation. 603 */ 604 unsigned long 605 timeval_to_jiffies(const struct timeval *value) 606 { 607 return __timespec_to_jiffies(value->tv_sec, 608 value->tv_usec * NSEC_PER_USEC); 609 } 610 EXPORT_SYMBOL(timeval_to_jiffies); 611 612 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value) 613 { 614 /* 615 * Convert jiffies to nanoseconds and separate with 616 * one divide. 617 */ 618 u32 rem; 619 620 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, 621 NSEC_PER_SEC, &rem); 622 value->tv_usec = rem / NSEC_PER_USEC; 623 } 624 EXPORT_SYMBOL(jiffies_to_timeval); 625 626 /* 627 * Convert jiffies/jiffies_64 to clock_t and back. 628 */ 629 clock_t jiffies_to_clock_t(unsigned long x) 630 { 631 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 632 # if HZ < USER_HZ 633 return x * (USER_HZ / HZ); 634 # else 635 return x / (HZ / USER_HZ); 636 # endif 637 #else 638 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ); 639 #endif 640 } 641 EXPORT_SYMBOL(jiffies_to_clock_t); 642 643 unsigned long clock_t_to_jiffies(unsigned long x) 644 { 645 #if (HZ % USER_HZ)==0 646 if (x >= ~0UL / (HZ / USER_HZ)) 647 return ~0UL; 648 return x * (HZ / USER_HZ); 649 #else 650 /* Don't worry about loss of precision here .. */ 651 if (x >= ~0UL / HZ * USER_HZ) 652 return ~0UL; 653 654 /* .. but do try to contain it here */ 655 return div_u64((u64)x * HZ, USER_HZ); 656 #endif 657 } 658 EXPORT_SYMBOL(clock_t_to_jiffies); 659 660 u64 jiffies_64_to_clock_t(u64 x) 661 { 662 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 663 # if HZ < USER_HZ 664 x = div_u64(x * USER_HZ, HZ); 665 # elif HZ > USER_HZ 666 x = div_u64(x, HZ / USER_HZ); 667 # else 668 /* Nothing to do */ 669 # endif 670 #else 671 /* 672 * There are better ways that don't overflow early, 673 * but even this doesn't overflow in hundreds of years 674 * in 64 bits, so.. 675 */ 676 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ)); 677 #endif 678 return x; 679 } 680 EXPORT_SYMBOL(jiffies_64_to_clock_t); 681 682 u64 nsec_to_clock_t(u64 x) 683 { 684 #if (NSEC_PER_SEC % USER_HZ) == 0 685 return div_u64(x, NSEC_PER_SEC / USER_HZ); 686 #elif (USER_HZ % 512) == 0 687 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512); 688 #else 689 /* 690 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024, 691 * overflow after 64.99 years. 692 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ... 693 */ 694 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ); 695 #endif 696 } 697 698 /** 699 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64 700 * 701 * @n: nsecs in u64 702 * 703 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. 704 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed 705 * for scheduler, not for use in device drivers to calculate timeout value. 706 * 707 * note: 708 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) 709 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years 710 */ 711 u64 nsecs_to_jiffies64(u64 n) 712 { 713 #if (NSEC_PER_SEC % HZ) == 0 714 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */ 715 return div_u64(n, NSEC_PER_SEC / HZ); 716 #elif (HZ % 512) == 0 717 /* overflow after 292 years if HZ = 1024 */ 718 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512); 719 #else 720 /* 721 * Generic case - optimized for cases where HZ is a multiple of 3. 722 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc. 723 */ 724 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ); 725 #endif 726 } 727 EXPORT_SYMBOL(nsecs_to_jiffies64); 728 729 /** 730 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies 731 * 732 * @n: nsecs in u64 733 * 734 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. 735 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed 736 * for scheduler, not for use in device drivers to calculate timeout value. 737 * 738 * note: 739 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) 740 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years 741 */ 742 unsigned long nsecs_to_jiffies(u64 n) 743 { 744 return (unsigned long)nsecs_to_jiffies64(n); 745 } 746 EXPORT_SYMBOL_GPL(nsecs_to_jiffies); 747 748 /* 749 * Add two timespec values and do a safety check for overflow. 750 * It's assumed that both values are valid (>= 0) 751 */ 752 struct timespec timespec_add_safe(const struct timespec lhs, 753 const struct timespec rhs) 754 { 755 struct timespec res; 756 757 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec, 758 lhs.tv_nsec + rhs.tv_nsec); 759 760 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec) 761 res.tv_sec = TIME_T_MAX; 762 763 return res; 764 } 765