kern_time.c revision 33690
1/* 2 * Copyright (c) 1982, 1986, 1989, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)kern_time.c 8.1 (Berkeley) 6/10/93 34 * $Id: kern_time.c,v 1.40 1997/11/07 08:52:58 phk Exp $ 35 */ 36 37#include <sys/param.h> 38#include <sys/sysproto.h> 39#include <sys/resourcevar.h> 40#include <sys/signalvar.h> 41#include <sys/kernel.h> 42#include <sys/systm.h> 43#include <sys/sysent.h> 44#include <sys/proc.h> 45#include <sys/time.h> 46#include <sys/vnode.h> 47#include <vm/vm.h> 48#include <vm/vm_extern.h> 49 50struct timezone tz; 51 52/* 53 * Time of day and interval timer support. 54 * 55 * These routines provide the kernel entry points to get and set 56 * the time-of-day and per-process interval timers. Subroutines 57 * here provide support for adding and subtracting timeval structures 58 * and decrementing interval timers, optionally reloading the interval 59 * timers when they expire. 60 */ 61 62static int nanosleep1 __P((struct proc *p, struct timespec *rqt, 63 struct timespec *rmt)); 64static int settime __P((struct timeval *)); 65static void timevalfix __P((struct timeval *)); 66static void no_lease_updatetime __P((int)); 67 68static void 69no_lease_updatetime(deltat) 70 int deltat; 71{ 72} 73 74void (*lease_updatetime) __P((int)) = no_lease_updatetime; 75 76static int 77settime(tv) 78 struct timeval *tv; 79{ 80 struct timeval delta; 81 struct timespec ts; 82 struct proc *p; 83 int s; 84 85 /* 86 * Must not set clock backwards in highly secure mode. 87 */ 88 s = splclock(); 89 delta.tv_sec = tv->tv_sec - time.tv_sec; 90 delta.tv_usec = tv->tv_usec - time.tv_usec; 91 splx(s); 92 timevalfix(&delta); 93 if (delta.tv_sec < 0 && securelevel > 1) 94 return (EPERM); 95 96 s = splclock(); 97 /* 98 * Recalculate delta directly to minimize clock interrupt 99 * latency. Fix it after the ipl has been lowered. 100 */ 101 delta.tv_sec = tv->tv_sec - time.tv_sec; 102 delta.tv_usec = tv->tv_usec - time.tv_usec; 103 ts.tv_sec = tv->tv_sec; 104 ts.tv_nsec = tv->tv_usec * 1000; 105 set_timecounter(&ts); 106 /* 107 * XXX should arrange for microtime() to agree with *tv if 108 * it is called now. As it is, it may add up to about 109 * `tick' unwanted usec. 110 * Another problem is that clock interrupts may occur at 111 * other than multiples of `tick'. It's not worth fixing 112 * this here, since the problem is also caused by tick 113 * adjustments. 114 */ 115 (void) splsoftclock(); 116 timevalfix(&delta); 117 timevaladd(&boottime, &delta); 118 timevaladd(&runtime, &delta); 119 for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) { 120 if (timerisset(&p->p_realtimer.it_value)) 121 timevaladd(&p->p_realtimer.it_value, &delta); 122 if (p->p_sleepend) 123 timevaladd(p->p_sleepend, &delta); 124 } 125 lease_updatetime(delta.tv_sec); 126 splx(s); 127 resettodr(); 128 return (0); 129} 130 131#ifndef _SYS_SYSPROTO_H_ 132struct clock_gettime_args { 133 clockid_t clock_id; 134 struct timespec *tp; 135}; 136#endif 137 138/* ARGSUSED */ 139int 140clock_gettime(p, uap) 141 struct proc *p; 142 struct clock_gettime_args *uap; 143{ 144 struct timespec ats; 145 146 if (SCARG(uap, clock_id) != CLOCK_REALTIME) 147 return (EINVAL); 148 nanotime(&ats); 149 return (copyout(&ats, SCARG(uap, tp), sizeof(ats))); 150} 151 152#ifndef _SYS_SYSPROTO_H_ 153struct clock_settime_args { 154 clockid_t clock_id; 155 const struct timespec *tp; 156}; 157#endif 158 159/* ARGSUSED */ 160int 161clock_settime(p, uap) 162 struct proc *p; 163 struct clock_settime_args *uap; 164{ 165 struct timeval atv; 166 struct timespec ats; 167 int error; 168 169 if ((error = suser(p->p_ucred, &p->p_acflag)) != 0) 170 return (error); 171 if (SCARG(uap, clock_id) != CLOCK_REALTIME) 172 return (EINVAL); 173 if ((error = copyin(SCARG(uap, tp), &ats, sizeof(ats))) != 0) 174 return (error); 175 if (ats.tv_nsec < 0 || ats.tv_nsec >= 1000000000) 176 return (EINVAL); 177 TIMESPEC_TO_TIMEVAL(&atv, &ats); 178 if ((error = settime(&atv))) 179 return (error); 180 return (0); 181} 182 183#ifndef _SYS_SYSPROTO_H_ 184struct clock_getres_args { 185 clockid_t clock_id; 186 struct timespec *tp; 187}; 188#endif 189 190int 191clock_getres(p, uap) 192 struct proc *p; 193 struct clock_getres_args *uap; 194{ 195 struct timespec ts; 196 int error; 197 198 if (SCARG(uap, clock_id) != CLOCK_REALTIME) 199 return (EINVAL); 200 error = 0; 201 if (SCARG(uap, tp)) { 202 ts.tv_sec = 0; 203 ts.tv_nsec = 1000000000 / timecounter->frequency; 204 error = copyout(&ts, SCARG(uap, tp), sizeof(ts)); 205 } 206 return (error); 207} 208 209static int nanowait; 210 211static int 212nanosleep1(p, rqt, rmt) 213 struct proc *p; 214 struct timespec *rqt, *rmt; 215{ 216 struct timeval atv, utv, rtv; 217 int error, s, timo, i, n; 218 219 if (rqt->tv_nsec < 0 || rqt->tv_nsec >= 1000000000) 220 return (EINVAL); 221 if (rqt->tv_sec < 0 || rqt->tv_sec == 0 && rqt->tv_nsec == 0) 222 return (0); 223 TIMESPEC_TO_TIMEVAL(&atv, rqt) 224 225 if (itimerfix(&atv)) { 226 n = atv.tv_sec / 100000000; 227 rtv = atv; 228 rtv.tv_sec %= 100000000; 229 (void)itimerfix(&rtv); 230 } else 231 n = 0; 232 233 for (i = 0, error = EWOULDBLOCK; i <= n && error == EWOULDBLOCK; i++) { 234 if (n > 0) { 235 if (i == n) 236 atv = rtv; 237 else { 238 atv.tv_sec = 100000000; 239 atv.tv_usec = 0; 240 } 241 } 242 /* 243 * XXX this is not as careful as settimeofday() about minimising 244 * interrupt latency. The hzto() interface is inconvenient as usual. 245 */ 246 s = splclock(); 247 timevaladd(&atv, &time); 248 timo = hzto(&atv); 249 splx(s); 250 251 p->p_sleepend = &atv; 252 error = tsleep(&nanowait, PWAIT | PCATCH, "nanslp", timo); 253 p->p_sleepend = NULL; 254 if (error == ERESTART) 255 error = EINTR; 256 if (rmt != NULL && (i == n || error != EWOULDBLOCK)) { 257 /*- 258 * XXX this is unnecessary and possibly wrong if the timeout 259 * expired. Then the remaining time should be zero. If the 260 * calculation gives a nonzero value, then we have a bug. 261 * (1) if settimeofday() was called, then the calculation is 262 * probably wrong, since `time' has probably become 263 * inconsistent with the ending time `atv'. 264 * XXX (1) should be fixed now with p->p_sleepend; 265 * (2) otherwise, our calculation of `timo' was wrong, perhaps 266 * due to `tick' being wrong when hzto() was called or 267 * changing afterwards (it can be wrong or change due to 268 * hzto() not knowing about adjtime(2) or tickadj(8)). 269 * Then we should be sleeping again instead instead of 270 * returning. Rounding up in hzto() probably fixes this 271 * problem for small timeouts, but the absolute error may 272 * be large for large timeouts. 273 */ 274 s = splclock(); 275 utv = time; 276 splx(s); 277 if (i != n) { 278 atv.tv_sec += (n - i - 1) * 100000000; 279 timevaladd(&atv, &rtv); 280 } 281 timevalsub(&atv, &utv); 282 if (atv.tv_sec < 0) 283 timerclear(&atv); 284 TIMEVAL_TO_TIMESPEC(&atv, rmt); 285 } 286 } 287 return (error == EWOULDBLOCK ? 0 : error); 288} 289 290#ifndef _SYS_SYSPROTO_H_ 291struct nanosleep_args { 292 struct timespec *rqtp; 293 struct timespec *rmtp; 294}; 295#endif 296 297/* ARGSUSED */ 298int 299nanosleep(p, uap) 300 struct proc *p; 301 struct nanosleep_args *uap; 302{ 303 struct timespec rmt, rqt; 304 int error, error2; 305 306 error = copyin(SCARG(uap, rqtp), &rqt, sizeof(rqt)); 307 if (error) 308 return (error); 309 if (SCARG(uap, rmtp)) 310 if (!useracc((caddr_t)SCARG(uap, rmtp), sizeof(rmt), B_WRITE)) 311 return (EFAULT); 312 error = nanosleep1(p, &rqt, &rmt); 313 if (SCARG(uap, rmtp)) { 314 error2 = copyout(&rmt, SCARG(uap, rmtp), sizeof(rmt)); 315 if (error2) /* XXX shouldn't happen, did useracc() above */ 316 return (error2); 317 } 318 return (error); 319} 320 321#ifndef _SYS_SYSPROTO_H_ 322struct signanosleep_args { 323 struct timespec *rqtp; 324 struct timespec *rmtp; 325 sigset_t *mask; 326}; 327#endif 328 329/* ARGSUSED */ 330int 331signanosleep(p, uap) 332 struct proc *p; 333 struct signanosleep_args *uap; 334{ 335 struct timespec rmt, rqt; 336 int error, error2; 337 sigset_t mask; 338 339 error = copyin(SCARG(uap, rqtp), &rqt, sizeof(rqt)); 340 if (error) 341 return (error); 342 if (SCARG(uap, rmtp)) 343 if (!useracc((caddr_t)SCARG(uap, rmtp), sizeof(rmt), B_WRITE)) 344 return (EFAULT); 345 error = copyin(SCARG(uap, mask), &mask, sizeof(mask)); 346 if (error) 347 return (error); 348 349 /* change mask for sleep */ 350 p->p_sigmask = mask &~ sigcantmask; 351 352 error = nanosleep1(p, &rqt, &rmt); 353 354 if (SCARG(uap, rmtp)) { 355 error2 = copyout(&rmt, SCARG(uap, rmtp), sizeof(rmt)); 356 if (error2) /* XXX shouldn't happen, did useracc() above */ 357 return (error2); 358 } 359 return (error); 360} 361 362#ifndef _SYS_SYSPROTO_H_ 363struct gettimeofday_args { 364 struct timeval *tp; 365 struct timezone *tzp; 366}; 367#endif 368/* ARGSUSED */ 369int 370gettimeofday(p, uap) 371 struct proc *p; 372 register struct gettimeofday_args *uap; 373{ 374 struct timeval atv; 375 int error = 0; 376 377 if (uap->tp) { 378 microtime(&atv); 379 if ((error = copyout((caddr_t)&atv, (caddr_t)uap->tp, 380 sizeof (atv)))) 381 return (error); 382 } 383 if (uap->tzp) 384 error = copyout((caddr_t)&tz, (caddr_t)uap->tzp, 385 sizeof (tz)); 386 return (error); 387} 388 389#ifndef _SYS_SYSPROTO_H_ 390struct settimeofday_args { 391 struct timeval *tv; 392 struct timezone *tzp; 393}; 394#endif 395/* ARGSUSED */ 396int 397settimeofday(p, uap) 398 struct proc *p; 399 struct settimeofday_args *uap; 400{ 401 struct timeval atv; 402 struct timezone atz; 403 int error; 404 405 if ((error = suser(p->p_ucred, &p->p_acflag))) 406 return (error); 407 /* Verify all parameters before changing time. */ 408 if (uap->tv) { 409 if ((error = copyin((caddr_t)uap->tv, (caddr_t)&atv, 410 sizeof(atv)))) 411 return (error); 412 if (atv.tv_usec < 0 || atv.tv_usec >= 1000000) 413 return (EINVAL); 414 } 415 if (uap->tzp && 416 (error = copyin((caddr_t)uap->tzp, (caddr_t)&atz, sizeof(atz)))) 417 return (error); 418 if (uap->tv && (error = settime(&atv))) 419 return (error); 420 if (uap->tzp) 421 tz = atz; 422 return (0); 423} 424 425int tickdelta; /* current clock skew, us. per tick */ 426long timedelta; /* unapplied time correction, us. */ 427static long bigadj = 1000000; /* use 10x skew above bigadj us. */ 428 429#ifndef _SYS_SYSPROTO_H_ 430struct adjtime_args { 431 struct timeval *delta; 432 struct timeval *olddelta; 433}; 434#endif 435/* ARGSUSED */ 436int 437adjtime(p, uap) 438 struct proc *p; 439 register struct adjtime_args *uap; 440{ 441 struct timeval atv; 442 register long ndelta, ntickdelta, odelta; 443 int s, error; 444 445 if ((error = suser(p->p_ucred, &p->p_acflag))) 446 return (error); 447 if ((error = 448 copyin((caddr_t)uap->delta, (caddr_t)&atv, sizeof(struct timeval)))) 449 return (error); 450 451 /* 452 * Compute the total correction and the rate at which to apply it. 453 * Round the adjustment down to a whole multiple of the per-tick 454 * delta, so that after some number of incremental changes in 455 * hardclock(), tickdelta will become zero, lest the correction 456 * overshoot and start taking us away from the desired final time. 457 */ 458 ndelta = atv.tv_sec * 1000000 + atv.tv_usec; 459 if (ndelta > bigadj || ndelta < -bigadj) 460 ntickdelta = 10 * tickadj; 461 else 462 ntickdelta = tickadj; 463 if (ndelta % ntickdelta) 464 ndelta = ndelta / ntickdelta * ntickdelta; 465 466 /* 467 * To make hardclock()'s job easier, make the per-tick delta negative 468 * if we want time to run slower; then hardclock can simply compute 469 * tick + tickdelta, and subtract tickdelta from timedelta. 470 */ 471 if (ndelta < 0) 472 ntickdelta = -ntickdelta; 473 s = splclock(); 474 odelta = timedelta; 475 timedelta = ndelta; 476 tickdelta = ntickdelta; 477 splx(s); 478 479 if (uap->olddelta) { 480 atv.tv_sec = odelta / 1000000; 481 atv.tv_usec = odelta % 1000000; 482 (void) copyout((caddr_t)&atv, (caddr_t)uap->olddelta, 483 sizeof(struct timeval)); 484 } 485 return (0); 486} 487 488/* 489 * Get value of an interval timer. The process virtual and 490 * profiling virtual time timers are kept in the p_stats area, since 491 * they can be swapped out. These are kept internally in the 492 * way they are specified externally: in time until they expire. 493 * 494 * The real time interval timer is kept in the process table slot 495 * for the process, and its value (it_value) is kept as an 496 * absolute time rather than as a delta, so that it is easy to keep 497 * periodic real-time signals from drifting. 498 * 499 * Virtual time timers are processed in the hardclock() routine of 500 * kern_clock.c. The real time timer is processed by a timeout 501 * routine, called from the softclock() routine. Since a callout 502 * may be delayed in real time due to interrupt processing in the system, 503 * it is possible for the real time timeout routine (realitexpire, given below), 504 * to be delayed in real time past when it is supposed to occur. It 505 * does not suffice, therefore, to reload the real timer .it_value from the 506 * real time timers .it_interval. Rather, we compute the next time in 507 * absolute time the timer should go off. 508 */ 509#ifndef _SYS_SYSPROTO_H_ 510struct getitimer_args { 511 u_int which; 512 struct itimerval *itv; 513}; 514#endif 515/* ARGSUSED */ 516int 517getitimer(p, uap) 518 struct proc *p; 519 register struct getitimer_args *uap; 520{ 521 struct itimerval aitv; 522 int s; 523 524 if (uap->which > ITIMER_PROF) 525 return (EINVAL); 526 s = splclock(); 527 if (uap->which == ITIMER_REAL) { 528 /* 529 * Convert from absoulte to relative time in .it_value 530 * part of real time timer. If time for real time timer 531 * has passed return 0, else return difference between 532 * current time and time for the timer to go off. 533 */ 534 aitv = p->p_realtimer; 535 if (timerisset(&aitv.it_value)) 536 if (timercmp(&aitv.it_value, &time, <)) 537 timerclear(&aitv.it_value); 538 else 539 timevalsub(&aitv.it_value, &time); 540 } else 541 aitv = p->p_stats->p_timer[uap->which]; 542 splx(s); 543 return (copyout((caddr_t)&aitv, (caddr_t)uap->itv, 544 sizeof (struct itimerval))); 545} 546 547#ifndef _SYS_SYSPROTO_H_ 548struct setitimer_args { 549 u_int which; 550 struct itimerval *itv, *oitv; 551}; 552#endif 553/* ARGSUSED */ 554int 555setitimer(p, uap) 556 struct proc *p; 557 register struct setitimer_args *uap; 558{ 559 struct itimerval aitv; 560 register struct itimerval *itvp; 561 int s, error; 562 563 if (uap->which > ITIMER_PROF) 564 return (EINVAL); 565 itvp = uap->itv; 566 if (itvp && (error = copyin((caddr_t)itvp, (caddr_t)&aitv, 567 sizeof(struct itimerval)))) 568 return (error); 569 if ((uap->itv = uap->oitv) && 570 (error = getitimer(p, (struct getitimer_args *)uap))) 571 return (error); 572 if (itvp == 0) 573 return (0); 574 if (itimerfix(&aitv.it_value)) 575 return (EINVAL); 576 if (!timerisset(&aitv.it_value)) 577 timerclear(&aitv.it_interval); 578 else if (itimerfix(&aitv.it_interval)) 579 return (EINVAL); 580 s = splclock(); 581 if (uap->which == ITIMER_REAL) { 582 if (timerisset(&p->p_realtimer.it_value)) 583 untimeout(realitexpire, (caddr_t)p, p->p_ithandle); 584 if (timerisset(&aitv.it_value)) { 585 timevaladd(&aitv.it_value, &time); 586 p->p_ithandle = timeout(realitexpire, (caddr_t)p, 587 hzto(&aitv.it_value)); 588 } 589 p->p_realtimer = aitv; 590 } else 591 p->p_stats->p_timer[uap->which] = aitv; 592 splx(s); 593 return (0); 594} 595 596/* 597 * Real interval timer expired: 598 * send process whose timer expired an alarm signal. 599 * If time is not set up to reload, then just return. 600 * Else compute next time timer should go off which is > current time. 601 * This is where delay in processing this timeout causes multiple 602 * SIGALRM calls to be compressed into one. 603 * hzto() always adds 1 to allow for the time until the next clock 604 * interrupt being strictly less than 1 clock tick, but we don't want 605 * that here since we want to appear to be in sync with the clock 606 * interrupt even when we're delayed. 607 */ 608void 609realitexpire(arg) 610 void *arg; 611{ 612 register struct proc *p; 613 int s; 614 615 p = (struct proc *)arg; 616 psignal(p, SIGALRM); 617 if (!timerisset(&p->p_realtimer.it_interval)) { 618 timerclear(&p->p_realtimer.it_value); 619 return; 620 } 621 for (;;) { 622 s = splclock(); 623 timevaladd(&p->p_realtimer.it_value, 624 &p->p_realtimer.it_interval); 625 if (timercmp(&p->p_realtimer.it_value, &time, >)) { 626 p->p_ithandle = 627 timeout(realitexpire, (caddr_t)p, 628 hzto(&p->p_realtimer.it_value) - 1); 629 splx(s); 630 return; 631 } 632 splx(s); 633 } 634} 635 636/* 637 * Check that a proposed value to load into the .it_value or 638 * .it_interval part of an interval timer is acceptable, and 639 * fix it to have at least minimal value (i.e. if it is less 640 * than the resolution of the clock, round it up.) 641 */ 642int 643itimerfix(tv) 644 struct timeval *tv; 645{ 646 647 if (tv->tv_sec < 0 || tv->tv_sec > 100000000 || 648 tv->tv_usec < 0 || tv->tv_usec >= 1000000) 649 return (EINVAL); 650 if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick) 651 tv->tv_usec = tick; 652 return (0); 653} 654 655/* 656 * Decrement an interval timer by a specified number 657 * of microseconds, which must be less than a second, 658 * i.e. < 1000000. If the timer expires, then reload 659 * it. In this case, carry over (usec - old value) to 660 * reduce the value reloaded into the timer so that 661 * the timer does not drift. This routine assumes 662 * that it is called in a context where the timers 663 * on which it is operating cannot change in value. 664 */ 665int 666itimerdecr(itp, usec) 667 register struct itimerval *itp; 668 int usec; 669{ 670 671 if (itp->it_value.tv_usec < usec) { 672 if (itp->it_value.tv_sec == 0) { 673 /* expired, and already in next interval */ 674 usec -= itp->it_value.tv_usec; 675 goto expire; 676 } 677 itp->it_value.tv_usec += 1000000; 678 itp->it_value.tv_sec--; 679 } 680 itp->it_value.tv_usec -= usec; 681 usec = 0; 682 if (timerisset(&itp->it_value)) 683 return (1); 684 /* expired, exactly at end of interval */ 685expire: 686 if (timerisset(&itp->it_interval)) { 687 itp->it_value = itp->it_interval; 688 itp->it_value.tv_usec -= usec; 689 if (itp->it_value.tv_usec < 0) { 690 itp->it_value.tv_usec += 1000000; 691 itp->it_value.tv_sec--; 692 } 693 } else 694 itp->it_value.tv_usec = 0; /* sec is already 0 */ 695 return (0); 696} 697 698/* 699 * Add and subtract routines for timevals. 700 * N.B.: subtract routine doesn't deal with 701 * results which are before the beginning, 702 * it just gets very confused in this case. 703 * Caveat emptor. 704 */ 705void 706timevaladd(t1, t2) 707 struct timeval *t1, *t2; 708{ 709 710 t1->tv_sec += t2->tv_sec; 711 t1->tv_usec += t2->tv_usec; 712 timevalfix(t1); 713} 714 715void 716timevalsub(t1, t2) 717 struct timeval *t1, *t2; 718{ 719 720 t1->tv_sec -= t2->tv_sec; 721 t1->tv_usec -= t2->tv_usec; 722 timevalfix(t1); 723} 724 725static void 726timevalfix(t1) 727 struct timeval *t1; 728{ 729 730 if (t1->tv_usec < 0) { 731 t1->tv_sec--; 732 t1->tv_usec += 1000000; 733 } 734 if (t1->tv_usec >= 1000000) { 735 t1->tv_sec++; 736 t1->tv_usec -= 1000000; 737 } 738} 739