linux/kernel/time.c
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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/errno.h>
  34#include <linux/syscalls.h>
  35#include <linux/security.h>
  36#include <linux/fs.h>
  37#include <linux/module.h>
  38
  39#include <asm/uaccess.h>
  40#include <asm/unistd.h>
  41
  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.
  45 */
  46struct timezone sys_tz;
  47
  48EXPORT_SYMBOL(sys_tz);
  49
  50#ifdef __ARCH_WANT_SYS_TIME
  51
  52/*
  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).
  57 */
  58asmlinkage long sys_time(time_t __user * tloc)
  59{
  60        time_t i;
  61        struct timeval tv;
  62
  63        do_gettimeofday(&tv);
  64        i = tv.tv_sec;
  65
  66        if (tloc) {
  67                if (put_user(i,tloc))
  68                        i = -EFAULT;
  69        }
  70        return i;
  71}
  72
  73/*
  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).
  78 */
  79 
  80asmlinkage long sys_stime(time_t __user *tptr)
  81{
  82        struct timespec tv;
  83        int err;
  84
  85        if (get_user(tv.tv_sec, tptr))
  86                return -EFAULT;
  87
  88        tv.tv_nsec = 0;
  89
  90        err = security_settime(&tv, NULL);
  91        if (err)
  92                return err;
  93
  94        do_settimeofday(&tv);
  95        return 0;
  96}
  97
  98#endif /* __ARCH_WANT_SYS_TIME */
  99
 100asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
 101{
 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;
 107        }
 108        if (unlikely(tz != NULL)) {
 109                if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
 110                        return -EFAULT;
 111        }
 112        return 0;
 113}
 114
 115/*
 116 * Adjust the time obtained from the CMOS to be UTC time instead of
 117 * local time.
 118 * 
 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....
 124 *
 125 *                                              - TYT, 1992-01-01
 126 *
 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.
 130 */
 131static inline void warp_clock(void)
 132{
 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        time_interpolator_reset();
 137        write_sequnlock_irq(&xtime_lock);
 138        clock_was_set();
 139}
 140
 141/*
 142 * In case for some reason the CMOS clock has not already been running
 143 * in UTC, but in some local time: The first time we set the timezone,
 144 * we will warp the clock so that it is ticking UTC time instead of
 145 * local time. Presumably, if someone is setting the timezone then we
 146 * are running in an environment where the programs understand about
 147 * timezones. This should be done at boot time in the /etc/rc script,
 148 * as soon as possible, so that the clock can be set right. Otherwise,
 149 * various programs will get confused when the clock gets warped.
 150 */
 151
 152int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
 153{
 154        static int firsttime = 1;
 155        int error = 0;
 156
 157        if (tv && !timespec_valid(tv))
 158                return -EINVAL;
 159
 160        error = security_settime(tv, tz);
 161        if (error)
 162                return error;
 163
 164        if (tz) {
 165                /* SMP safe, global irq locking makes it work. */
 166                sys_tz = *tz;
 167                if (firsttime) {
 168                        firsttime = 0;
 169                        if (!tv)
 170                                warp_clock();
 171                }
 172        }
 173        if (tv)
 174        {
 175                /* SMP safe, again the code in arch/foo/time.c should
 176                 * globally block out interrupts when it runs.
 177                 */
 178                return do_settimeofday(tv);
 179        }
 180        return 0;
 181}
 182
 183asmlinkage long sys_settimeofday(struct timeval __user *tv,
 184                                struct timezone __user *tz)
 185{
 186        struct timeval user_tv;
 187        struct timespec new_ts;
 188        struct timezone new_tz;
 189
 190        if (tv) {
 191                if (copy_from_user(&user_tv, tv, sizeof(*tv)))
 192                        return -EFAULT;
 193                new_ts.tv_sec = user_tv.tv_sec;
 194                new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
 195        }
 196        if (tz) {
 197                if (copy_from_user(&new_tz, tz, sizeof(*tz)))
 198                        return -EFAULT;
 199        }
 200
 201        return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
 202}
 203
 204asmlinkage long sys_adjtimex(struct timex __user *txc_p)
 205{
 206        struct timex txc;               /* Local copy of parameter */
 207        int ret;
 208
 209        /* Copy the user data space into the kernel copy
 210         * structure. But bear in mind that the structures
 211         * may change
 212         */
 213        if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
 214                return -EFAULT;
 215        ret = do_adjtimex(&txc);
 216        return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
 217}
 218
 219inline struct timespec current_kernel_time(void)
 220{
 221        struct timespec now;
 222        unsigned long seq;
 223
 224        do {
 225                seq = read_seqbegin(&xtime_lock);
 226                
 227                now = xtime;
 228        } while (read_seqretry(&xtime_lock, seq));
 229
 230        return now; 
 231}
 232
 233EXPORT_SYMBOL(current_kernel_time);
 234
 235/**
 236 * current_fs_time - Return FS time
 237 * @sb: Superblock.
 238 *
 239 * Return the current time truncated to the time granularity supported by
 240 * the fs.
 241 */
 242struct timespec current_fs_time(struct super_block *sb)
 243{
 244        struct timespec now = current_kernel_time();
 245        return timespec_trunc(now, sb->s_time_gran);
 246}
 247EXPORT_SYMBOL(current_fs_time);
 248
 249/*
 250 * Convert jiffies to milliseconds and back.
 251 *
 252 * Avoid unnecessary multiplications/divisions in the
 253 * two most common HZ cases:
 254 */
 255unsigned int inline jiffies_to_msecs(const unsigned long j)
 256{
 257#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
 258        return (MSEC_PER_SEC / HZ) * j;
 259#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
 260        return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
 261#else
 262        return (j * MSEC_PER_SEC) / HZ;
 263#endif
 264}
 265EXPORT_SYMBOL(jiffies_to_msecs);
 266
 267unsigned int inline jiffies_to_usecs(const unsigned long j)
 268{
 269#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
 270        return (USEC_PER_SEC / HZ) * j;
 271#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
 272        return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
 273#else
 274        return (j * USEC_PER_SEC) / HZ;
 275#endif
 276}
 277EXPORT_SYMBOL(jiffies_to_usecs);
 278
 279/**
 280 * timespec_trunc - Truncate timespec to a granularity
 281 * @t: Timespec
 282 * @gran: Granularity in ns.
 283 *
 284 * Truncate a timespec to a granularity. gran must be smaller than a second.
 285 * Always rounds down.
 286 *
 287 * This function should be only used for timestamps returned by
 288 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
 289 * it doesn't handle the better resolution of the later.
 290 */
 291struct timespec timespec_trunc(struct timespec t, unsigned gran)
 292{
 293        /*
 294         * Division is pretty slow so avoid it for common cases.
 295         * Currently current_kernel_time() never returns better than
 296         * jiffies resolution. Exploit that.
 297         */
 298        if (gran <= jiffies_to_usecs(1) * 1000) {
 299                /* nothing */
 300        } else if (gran == 1000000000) {
 301                t.tv_nsec = 0;
 302        } else {
 303                t.tv_nsec -= t.tv_nsec % gran;
 304        }
 305        return t;
 306}
 307EXPORT_SYMBOL(timespec_trunc);
 308
 309#ifdef CONFIG_TIME_INTERPOLATION
 310void getnstimeofday (struct timespec *tv)
 311{
 312        unsigned long seq,sec,nsec;
 313
 314        do {
 315                seq = read_seqbegin(&xtime_lock);
 316                sec = xtime.tv_sec;
 317                nsec = xtime.tv_nsec+time_interpolator_get_offset();
 318        } while (unlikely(read_seqretry(&xtime_lock, seq)));
 319
 320        while (unlikely(nsec >= NSEC_PER_SEC)) {
 321                nsec -= NSEC_PER_SEC;
 322                ++sec;
 323        }
 324        tv->tv_sec = sec;
 325        tv->tv_nsec = nsec;
 326}
 327EXPORT_SYMBOL_GPL(getnstimeofday);
 328
 329int do_settimeofday (struct timespec *tv)
 330{
 331        time_t wtm_sec, sec = tv->tv_sec;
 332        long wtm_nsec, nsec = tv->tv_nsec;
 333
 334        if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
 335                return -EINVAL;
 336
 337        write_seqlock_irq(&xtime_lock);
 338        {
 339                wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
 340                wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
 341
 342                set_normalized_timespec(&xtime, sec, nsec);
 343                set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
 344
 345                time_adjust = 0;                /* stop active adjtime() */
 346                time_status |= STA_UNSYNC;
 347                time_maxerror = NTP_PHASE_LIMIT;
 348                time_esterror = NTP_PHASE_LIMIT;
 349                time_interpolator_reset();
 350        }
 351        write_sequnlock_irq(&xtime_lock);
 352        clock_was_set();
 353        return 0;
 354}
 355EXPORT_SYMBOL(do_settimeofday);
 356
 357void do_gettimeofday (struct timeval *tv)
 358{
 359        unsigned long seq, nsec, usec, sec, offset;
 360        do {
 361                seq = read_seqbegin(&xtime_lock);
 362                offset = time_interpolator_get_offset();
 363                sec = xtime.tv_sec;
 364                nsec = xtime.tv_nsec;
 365        } while (unlikely(read_seqretry(&xtime_lock, seq)));
 366
 367        usec = (nsec + offset) / 1000;
 368
 369        while (unlikely(usec >= USEC_PER_SEC)) {
 370                usec -= USEC_PER_SEC;
 371                ++sec;
 372        }
 373
 374        tv->tv_sec = sec;
 375        tv->tv_usec = usec;
 376}
 377
 378EXPORT_SYMBOL(do_gettimeofday);
 379
 380
 381#else
 382#ifndef CONFIG_GENERIC_TIME
 383/*
 384 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
 385 * and therefore only yields usec accuracy
 386 */
 387void getnstimeofday(struct timespec *tv)
 388{
 389        struct timeval x;
 390
 391        do_gettimeofday(&x);
 392        tv->tv_sec = x.tv_sec;
 393        tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
 394}
 395EXPORT_SYMBOL_GPL(getnstimeofday);
 396#endif
 397#endif
 398
 399/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
 400 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
 401 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
 402 *
 403 * [For the Julian calendar (which was used in Russia before 1917,
 404 * Britain & colonies before 1752, anywhere else before 1582,
 405 * and is still in use by some communities) leave out the
 406 * -year/100+year/400 terms, and add 10.]
 407 *
 408 * This algorithm was first published by Gauss (I think).
 409 *
 410 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
 411 * machines were long is 32-bit! (However, as time_t is signed, we
 412 * will already get problems at other places on 2038-01-19 03:14:08)
 413 */
 414unsigned long
 415mktime(const unsigned int year0, const unsigned int mon0,
 416       const unsigned int day, const unsigned int hour,
 417       const unsigned int min, const unsigned int sec)
 418{
 419        unsigned int mon = mon0, year = year0;
 420
 421        /* 1..12 -> 11,12,1..10 */
 422        if (0 >= (int) (mon -= 2)) {
 423                mon += 12;      /* Puts Feb last since it has leap day */
 424                year -= 1;
 425        }
 426
 427        return ((((unsigned long)
 428                  (year/4 - year/100 + year/400 + 367*mon/12 + day) +
 429                  year*365 - 719499
 430            )*24 + hour /* now have hours */
 431          )*60 + min /* now have minutes */
 432        )*60 + sec; /* finally seconds */
 433}
 434
 435EXPORT_SYMBOL(mktime);
 436
 437/**
 438 * set_normalized_timespec - set timespec sec and nsec parts and normalize
 439 *
 440 * @ts:         pointer to timespec variable to be set
 441 * @sec:        seconds to set
 442 * @nsec:       nanoseconds to set
 443 *
 444 * Set seconds and nanoseconds field of a timespec variable and
 445 * normalize to the timespec storage format
 446 *
 447 * Note: The tv_nsec part is always in the range of
 448 *      0 <= tv_nsec < NSEC_PER_SEC
 449 * For negative values only the tv_sec field is negative !
 450 */
 451void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
 452{
 453        while (nsec >= NSEC_PER_SEC) {
 454                nsec -= NSEC_PER_SEC;
 455                ++sec;
 456        }
 457        while (nsec < 0) {
 458                nsec += NSEC_PER_SEC;
 459                --sec;
 460        }
 461        ts->tv_sec = sec;
 462        ts->tv_nsec = nsec;
 463}
 464
 465/**
 466 * ns_to_timespec - Convert nanoseconds to timespec
 467 * @nsec:       the nanoseconds value to be converted
 468 *
 469 * Returns the timespec representation of the nsec parameter.
 470 */
 471struct timespec ns_to_timespec(const s64 nsec)
 472{
 473        struct timespec ts;
 474
 475        if (!nsec)
 476                return (struct timespec) {0, 0};
 477
 478        ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC, &ts.tv_nsec);
 479        if (unlikely(nsec < 0))
 480                set_normalized_timespec(&ts, ts.tv_sec, ts.tv_nsec);
 481
 482        return ts;
 483}
 484EXPORT_SYMBOL(ns_to_timespec);
 485
 486/**
 487 * ns_to_timeval - Convert nanoseconds to timeval
 488 * @nsec:       the nanoseconds value to be converted
 489 *
 490 * Returns the timeval representation of the nsec parameter.
 491 */
 492struct timeval ns_to_timeval(const s64 nsec)
 493{
 494        struct timespec ts = ns_to_timespec(nsec);
 495        struct timeval tv;
 496
 497        tv.tv_sec = ts.tv_sec;
 498        tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
 499
 500        return tv;
 501}
 502EXPORT_SYMBOL(ns_to_timeval);
 503
 504/*
 505 * When we convert to jiffies then we interpret incoming values
 506 * the following way:
 507 *
 508 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
 509 *
 510 * - 'too large' values [that would result in larger than
 511 *   MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
 512 *
 513 * - all other values are converted to jiffies by either multiplying
 514 *   the input value by a factor or dividing it with a factor
 515 *
 516 * We must also be careful about 32-bit overflows.
 517 */
 518unsigned long msecs_to_jiffies(const unsigned int m)
 519{
 520        /*
 521         * Negative value, means infinite timeout:
 522         */
 523        if ((int)m < 0)
 524                return MAX_JIFFY_OFFSET;
 525
 526#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
 527        /*
 528         * HZ is equal to or smaller than 1000, and 1000 is a nice
 529         * round multiple of HZ, divide with the factor between them,
 530         * but round upwards:
 531         */
 532        return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
 533#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
 534        /*
 535         * HZ is larger than 1000, and HZ is a nice round multiple of
 536         * 1000 - simply multiply with the factor between them.
 537         *
 538         * But first make sure the multiplication result cannot
 539         * overflow:
 540         */
 541        if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
 542                return MAX_JIFFY_OFFSET;
 543
 544        return m * (HZ / MSEC_PER_SEC);
 545#else
 546        /*
 547         * Generic case - multiply, round and divide. But first
 548         * check that if we are doing a net multiplication, that
 549         * we wouldnt overflow:
 550         */
 551        if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
 552                return MAX_JIFFY_OFFSET;
 553
 554        return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
 555#endif
 556}
 557EXPORT_SYMBOL(msecs_to_jiffies);
 558
 559unsigned long usecs_to_jiffies(const unsigned int u)
 560{
 561        if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
 562                return MAX_JIFFY_OFFSET;
 563#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
 564        return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
 565#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
 566        return u * (HZ / USEC_PER_SEC);
 567#else
 568        return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC;
 569#endif
 570}
 571EXPORT_SYMBOL(usecs_to_jiffies);
 572
 573/*
 574 * The TICK_NSEC - 1 rounds up the value to the next resolution.  Note
 575 * that a remainder subtract here would not do the right thing as the
 576 * resolution values don't fall on second boundries.  I.e. the line:
 577 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
 578 *
 579 * Rather, we just shift the bits off the right.
 580 *
 581 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
 582 * value to a scaled second value.
 583 */
 584unsigned long
 585timespec_to_jiffies(const struct timespec *value)
 586{
 587        unsigned long sec = value->tv_sec;
 588        long nsec = value->tv_nsec + TICK_NSEC - 1;
 589
 590        if (sec >= MAX_SEC_IN_JIFFIES){
 591                sec = MAX_SEC_IN_JIFFIES;
 592                nsec = 0;
 593        }
 594        return (((u64)sec * SEC_CONVERSION) +
 595                (((u64)nsec * NSEC_CONVERSION) >>
 596                 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
 597
 598}
 599EXPORT_SYMBOL(timespec_to_jiffies);
 600
 601void
 602jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
 603{
 604        /*
 605         * Convert jiffies to nanoseconds and separate with
 606         * one divide.
 607         */
 608        u64 nsec = (u64)jiffies * TICK_NSEC;
 609        value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec);
 610}
 611EXPORT_SYMBOL(jiffies_to_timespec);
 612
 613/* Same for "timeval"
 614 *
 615 * Well, almost.  The problem here is that the real system resolution is
 616 * in nanoseconds and the value being converted is in micro seconds.
 617 * Also for some machines (those that use HZ = 1024, in-particular),
 618 * there is a LARGE error in the tick size in microseconds.
 619
 620 * The solution we use is to do the rounding AFTER we convert the
 621 * microsecond part.  Thus the USEC_ROUND, the bits to be shifted off.
 622 * Instruction wise, this should cost only an additional add with carry
 623 * instruction above the way it was done above.
 624 */
 625unsigned long
 626timeval_to_jiffies(const struct timeval *value)
 627{
 628        unsigned long sec = value->tv_sec;
 629        long usec = value->tv_usec;
 630
 631        if (sec >= MAX_SEC_IN_JIFFIES){
 632                sec = MAX_SEC_IN_JIFFIES;
 633                usec = 0;
 634        }
 635        return (((u64)sec * SEC_CONVERSION) +
 636                (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
 637                 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
 638}
 639EXPORT_SYMBOL(timeval_to_jiffies);
 640
 641void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
 642{
 643        /*
 644         * Convert jiffies to nanoseconds and separate with
 645         * one divide.
 646         */
 647        u64 nsec = (u64)jiffies * TICK_NSEC;
 648        long tv_usec;
 649
 650        value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &tv_usec);
 651        tv_usec /= NSEC_PER_USEC;
 652        value->tv_usec = tv_usec;
 653}
 654EXPORT_SYMBOL(jiffies_to_timeval);
 655
 656/*
 657 * Convert jiffies/jiffies_64 to clock_t and back.
 658 */
 659clock_t jiffies_to_clock_t(long x)
 660{
 661#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
 662        return x / (HZ / USER_HZ);
 663#else
 664        u64 tmp = (u64)x * TICK_NSEC;
 665        do_div(tmp, (NSEC_PER_SEC / USER_HZ));
 666        return (long)tmp;
 667#endif
 668}
 669EXPORT_SYMBOL(jiffies_to_clock_t);
 670
 671unsigned long clock_t_to_jiffies(unsigned long x)
 672{
 673#if (HZ % USER_HZ)==0
 674        if (x >= ~0UL / (HZ / USER_HZ))
 675                return ~0UL;
 676        return x * (HZ / USER_HZ);
 677#else
 678        u64 jif;
 679
 680        /* Don't worry about loss of precision here .. */
 681        if (x >= ~0UL / HZ * USER_HZ)
 682                return ~0UL;
 683
 684        /* .. but do try to contain it here */
 685        jif = x * (u64) HZ;
 686        do_div(jif, USER_HZ);
 687        return jif;
 688#endif
 689}
 690EXPORT_SYMBOL(clock_t_to_jiffies);
 691
 692u64 jiffies_64_to_clock_t(u64 x)
 693{
 694#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
 695        do_div(x, HZ / USER_HZ);
 696#else
 697        /*
 698         * There are better ways that don't overflow early,
 699         * but even this doesn't overflow in hundreds of years
 700         * in 64 bits, so..
 701         */
 702        x *= TICK_NSEC;
 703        do_div(x, (NSEC_PER_SEC / USER_HZ));
 704#endif
 705        return x;
 706}
 707
 708EXPORT_SYMBOL(jiffies_64_to_clock_t);
 709
 710u64 nsec_to_clock_t(u64 x)
 711{
 712#if (NSEC_PER_SEC % USER_HZ) == 0
 713        do_div(x, (NSEC_PER_SEC / USER_HZ));
 714#elif (USER_HZ % 512) == 0
 715        x *= USER_HZ/512;
 716        do_div(x, (NSEC_PER_SEC / 512));
 717#else
 718        /*
 719         * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
 720         * overflow after 64.99 years.
 721         * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
 722         */
 723        x *= 9;
 724        do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) /
 725                                  USER_HZ));
 726#endif
 727        return x;
 728}
 729
 730#if (BITS_PER_LONG < 64)
 731u64 get_jiffies_64(void)
 732{
 733        unsigned long seq;
 734        u64 ret;
 735
 736        do {
 737                seq = read_seqbegin(&xtime_lock);
 738                ret = jiffies_64;
 739        } while (read_seqretry(&xtime_lock, seq));
 740        return ret;
 741}
 742
 743EXPORT_SYMBOL(get_jiffies_64);
 744#endif
 745
 746EXPORT_SYMBOL(jiffies);
 747
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