kern_time.c

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    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  */
   35 
   36 #include <sys/cdefs.h>
   37 __FBSDID("$FreeBSD: releng/5.2/sys/kern/kern_time.c 121523 2003-10-26 02:19:00Z alfred $");
   38 
   39 #include "opt_mac.h"
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 #include <sys/lock.h>
   44 #include <sys/mutex.h>
   45 #include <sys/sysproto.h>
   46 #include <sys/resourcevar.h>
   47 #include <sys/signalvar.h>
   48 #include <sys/kernel.h>
   49 #include <sys/mac.h>
   50 #include <sys/sysent.h>
   51 #include <sys/proc.h>
   52 #include <sys/time.h>
   53 #include <sys/timetc.h>
   54 #include <sys/vnode.h>
   55 
   56 #include <vm/vm.h>
   57 #include <vm/vm_extern.h>
   58 
   59 int tz_minuteswest;
   60 int tz_dsttime;
   61 
   62 /*
   63  * Time of day and interval timer support.
   64  *
   65  * These routines provide the kernel entry points to get and set
   66  * the time-of-day and per-process interval timers.  Subroutines
   67  * here provide support for adding and subtracting timeval structures
   68  * and decrementing interval timers, optionally reloading the interval
   69  * timers when they expire.
   70  */
   71 
   72 static int      nanosleep1(struct thread *td, struct timespec *rqt,
   73                     struct timespec *rmt);
   74 static int      settime(struct thread *, struct timeval *);
   75 static void     timevalfix(struct timeval *);
   76 static void     no_lease_updatetime(int);
   77 
   78 static void 
   79 no_lease_updatetime(deltat)
   80         int deltat;
   81 {
   82 }
   83 
   84 void (*lease_updatetime)(int)  = no_lease_updatetime;
   85 
   86 static int
   87 settime(struct thread *td, struct timeval *tv)
   88 {
   89         struct timeval delta, tv1, tv2;
   90         static struct timeval maxtime, laststep;
   91         struct timespec ts;
   92         int s;
   93 
   94         s = splclock();
   95         microtime(&tv1);
   96         delta = *tv;
   97         timevalsub(&delta, &tv1);
   98 
   99         /*
  100          * If the system is secure, we do not allow the time to be 
  101          * set to a value earlier than 1 second less than the highest
  102          * time we have yet seen. The worst a miscreant can do in
  103          * this circumstance is "freeze" time. He couldn't go
  104          * back to the past.
  105          *
  106          * We similarly do not allow the clock to be stepped more
  107          * than one second, nor more than once per second. This allows
  108          * a miscreant to make the clock march double-time, but no worse.
  109          */
  110         if (securelevel_gt(td->td_ucred, 1) != 0) {
  111                 if (delta.tv_sec < 0 || delta.tv_usec < 0) {
  112                         /*
  113                          * Update maxtime to latest time we've seen.
  114                          */
  115                         if (tv1.tv_sec > maxtime.tv_sec)
  116                                 maxtime = tv1;
  117                         tv2 = *tv;
  118                         timevalsub(&tv2, &maxtime);
  119                         if (tv2.tv_sec < -1) {
  120                                 tv->tv_sec = maxtime.tv_sec - 1;
  121                                 printf("Time adjustment clamped to -1 second\n");
  122                         }
  123                 } else {
  124                         if (tv1.tv_sec == laststep.tv_sec) {
  125                                 splx(s);
  126                                 return (EPERM);
  127                         }
  128                         if (delta.tv_sec > 1) {
  129                                 tv->tv_sec = tv1.tv_sec + 1;
  130                                 printf("Time adjustment clamped to +1 second\n");
  131                         }
  132                         laststep = *tv;
  133                 }
  134         }
  135 
  136         ts.tv_sec = tv->tv_sec;
  137         ts.tv_nsec = tv->tv_usec * 1000;
  138         mtx_lock(&Giant);
  139         tc_setclock(&ts);
  140         (void) splsoftclock();
  141         lease_updatetime(delta.tv_sec);
  142         splx(s);
  143         resettodr();
  144         mtx_unlock(&Giant);
  145         return (0);
  146 }
  147 
  148 #ifndef _SYS_SYSPROTO_H_
  149 struct clock_gettime_args {
  150         clockid_t clock_id;
  151         struct  timespec *tp;
  152 };
  153 #endif
  154 
  155 /*
  156  * MPSAFE
  157  */
  158 /* ARGSUSED */
  159 int
  160 clock_gettime(struct thread *td, struct clock_gettime_args *uap)
  161 {
  162         struct timespec ats;
  163 
  164         if (uap->clock_id == CLOCK_REALTIME)
  165                 nanotime(&ats);
  166         else if (uap->clock_id == CLOCK_MONOTONIC)
  167                 nanouptime(&ats);
  168         else
  169                 return (EINVAL);
  170         return (copyout(&ats, uap->tp, sizeof(ats)));
  171 }
  172 
  173 #ifndef _SYS_SYSPROTO_H_
  174 struct clock_settime_args {
  175         clockid_t clock_id;
  176         const struct    timespec *tp;
  177 };
  178 #endif
  179 
  180 /*
  181  * MPSAFE
  182  */
  183 /* ARGSUSED */
  184 int
  185 clock_settime(struct thread *td, struct clock_settime_args *uap)
  186 {
  187         struct timeval atv;
  188         struct timespec ats;
  189         int error;
  190 
  191 #ifdef MAC
  192         error = mac_check_system_settime(td->td_ucred);
  193         if (error)
  194                 return (error);
  195 #endif
  196         if ((error = suser(td)) != 0)
  197                 return (error);
  198         if (uap->clock_id != CLOCK_REALTIME)
  199                 return (EINVAL);
  200         if ((error = copyin(uap->tp, &ats, sizeof(ats))) != 0)
  201                 return (error);
  202         if (ats.tv_nsec < 0 || ats.tv_nsec >= 1000000000)
  203                 return (EINVAL);
  204         /* XXX Don't convert nsec->usec and back */
  205         TIMESPEC_TO_TIMEVAL(&atv, &ats);
  206         error = settime(td, &atv);
  207         return (error);
  208 }
  209 
  210 #ifndef _SYS_SYSPROTO_H_
  211 struct clock_getres_args {
  212         clockid_t clock_id;
  213         struct  timespec *tp;
  214 };
  215 #endif
  216 
  217 int
  218 clock_getres(struct thread *td, struct clock_getres_args *uap)
  219 {
  220         struct timespec ts;
  221         int error;
  222 
  223         if (uap->clock_id != CLOCK_REALTIME)
  224                 return (EINVAL);
  225         error = 0;
  226         if (uap->tp) {
  227                 ts.tv_sec = 0;
  228                 /*
  229                  * Round up the result of the division cheaply by adding 1.
  230                  * Rounding up is especially important if rounding down
  231                  * would give 0.  Perfect rounding is unimportant.
  232                  */
  233                 ts.tv_nsec = 1000000000 / tc_getfrequency() + 1;
  234                 error = copyout(&ts, uap->tp, sizeof(ts));
  235         }
  236         return (error);
  237 }
  238 
  239 static int nanowait;
  240 
  241 static int
  242 nanosleep1(struct thread *td, struct timespec *rqt, struct timespec *rmt)
  243 {
  244         struct timespec ts, ts2, ts3;
  245         struct timeval tv;
  246         int error;
  247 
  248         if (rqt->tv_nsec < 0 || rqt->tv_nsec >= 1000000000)
  249                 return (EINVAL);
  250         if (rqt->tv_sec < 0 || (rqt->tv_sec == 0 && rqt->tv_nsec == 0))
  251                 return (0);
  252         getnanouptime(&ts);
  253         timespecadd(&ts, rqt);
  254         TIMESPEC_TO_TIMEVAL(&tv, rqt);
  255         for (;;) {
  256                 error = tsleep(&nanowait, PWAIT | PCATCH, "nanslp",
  257                     tvtohz(&tv));
  258                 getnanouptime(&ts2);
  259                 if (error != EWOULDBLOCK) {
  260                         if (error == ERESTART)
  261                                 error = EINTR;
  262                         if (rmt != NULL) {
  263                                 timespecsub(&ts, &ts2);
  264                                 if (ts.tv_sec < 0)
  265                                         timespecclear(&ts);
  266                                 *rmt = ts;
  267                         }
  268                         return (error);
  269                 }
  270                 if (timespeccmp(&ts2, &ts, >=))
  271                         return (0);
  272                 ts3 = ts;
  273                 timespecsub(&ts3, &ts2);
  274                 TIMESPEC_TO_TIMEVAL(&tv, &ts3);
  275         }
  276 }
  277 
  278 #ifndef _SYS_SYSPROTO_H_
  279 struct nanosleep_args {
  280         struct  timespec *rqtp;
  281         struct  timespec *rmtp;
  282 };
  283 #endif
  284 
  285 /* 
  286  * MPSAFE
  287  */
  288 /* ARGSUSED */
  289 int
  290 nanosleep(struct thread *td, struct nanosleep_args *uap)
  291 {
  292         struct timespec rmt, rqt;
  293         int error;
  294 
  295         error = copyin(uap->rqtp, &rqt, sizeof(rqt));
  296         if (error)
  297                 return (error);
  298 
  299         if (uap->rmtp &&
  300             !useracc((caddr_t)uap->rmtp, sizeof(rmt), VM_PROT_WRITE))
  301                         return (EFAULT);
  302         error = nanosleep1(td, &rqt, &rmt);
  303         if (error && uap->rmtp) {
  304                 int error2;
  305 
  306                 error2 = copyout(&rmt, uap->rmtp, sizeof(rmt));
  307                 if (error2)
  308                         error = error2;
  309         }
  310         return (error);
  311 }
  312 
  313 #ifndef _SYS_SYSPROTO_H_
  314 struct gettimeofday_args {
  315         struct  timeval *tp;
  316         struct  timezone *tzp;
  317 };
  318 #endif
  319 /*
  320  * MPSAFE
  321  */
  322 /* ARGSUSED */
  323 int
  324 gettimeofday(struct thread *td, struct gettimeofday_args *uap)
  325 {
  326         struct timeval atv;
  327         struct timezone rtz;
  328         int error = 0;
  329 
  330         if (uap->tp) {
  331                 microtime(&atv);
  332                 error = copyout(&atv, uap->tp, sizeof (atv));
  333         }
  334         if (error == 0 && uap->tzp != NULL) {
  335                 rtz.tz_minuteswest = tz_minuteswest;
  336                 rtz.tz_dsttime = tz_dsttime;
  337                 error = copyout(&rtz, uap->tzp, sizeof (rtz));
  338         }
  339         return (error);
  340 }
  341 
  342 #ifndef _SYS_SYSPROTO_H_
  343 struct settimeofday_args {
  344         struct  timeval *tv;
  345         struct  timezone *tzp;
  346 };
  347 #endif
  348 /*
  349  * MPSAFE
  350  */
  351 /* ARGSUSED */
  352 int
  353 settimeofday(struct thread *td, struct settimeofday_args *uap)
  354 {
  355         struct timeval atv;
  356         struct timezone atz;
  357         int error = 0;
  358 
  359 #ifdef MAC
  360         error = mac_check_system_settime(td->td_ucred);
  361         if (error)
  362                 return (error);
  363 #endif
  364         if ((error = suser(td)))
  365                 return (error);
  366         /* Verify all parameters before changing time. */
  367         if (uap->tv) {
  368                 if ((error = copyin(uap->tv, &atv, sizeof(atv))))
  369                         return (error);
  370                 if (atv.tv_usec < 0 || atv.tv_usec >= 1000000)
  371                         return (EINVAL);
  372         }
  373         if (uap->tzp &&
  374             (error = copyin(uap->tzp, &atz, sizeof(atz))))
  375                 return (error);
  376         
  377         if (uap->tv && (error = settime(td, &atv)))
  378                 return (error);
  379         if (uap->tzp) {
  380                 tz_minuteswest = atz.tz_minuteswest;
  381                 tz_dsttime = atz.tz_dsttime;
  382         }
  383         return (error);
  384 }
  385 /*
  386  * Get value of an interval timer.  The process virtual and
  387  * profiling virtual time timers are kept in the p_stats area, since
  388  * they can be swapped out.  These are kept internally in the
  389  * way they are specified externally: in time until they expire.
  390  *
  391  * The real time interval timer is kept in the process table slot
  392  * for the process, and its value (it_value) is kept as an
  393  * absolute time rather than as a delta, so that it is easy to keep
  394  * periodic real-time signals from drifting.
  395  *
  396  * Virtual time timers are processed in the hardclock() routine of
  397  * kern_clock.c.  The real time timer is processed by a timeout
  398  * routine, called from the softclock() routine.  Since a callout
  399  * may be delayed in real time due to interrupt processing in the system,
  400  * it is possible for the real time timeout routine (realitexpire, given below),
  401  * to be delayed in real time past when it is supposed to occur.  It
  402  * does not suffice, therefore, to reload the real timer .it_value from the
  403  * real time timers .it_interval.  Rather, we compute the next time in
  404  * absolute time the timer should go off.
  405  */
  406 #ifndef _SYS_SYSPROTO_H_
  407 struct getitimer_args {
  408         u_int   which;
  409         struct  itimerval *itv;
  410 };
  411 #endif
  412 /*
  413  * MPSAFE
  414  */
  415 int
  416 getitimer(struct thread *td, struct getitimer_args *uap)
  417 {
  418         struct proc *p = td->td_proc;
  419         struct timeval ctv;
  420         struct itimerval aitv;
  421 
  422         if (uap->which > ITIMER_PROF)
  423                 return (EINVAL);
  424 
  425         if (uap->which == ITIMER_REAL) {
  426                 /*
  427                  * Convert from absolute to relative time in .it_value
  428                  * part of real time timer.  If time for real time timer
  429                  * has passed return 0, else return difference between
  430                  * current time and time for the timer to go off.
  431                  */
  432                 PROC_LOCK(p);
  433                 aitv = p->p_realtimer;
  434                 PROC_UNLOCK(p);
  435                 if (timevalisset(&aitv.it_value)) {
  436                         getmicrouptime(&ctv);
  437                         if (timevalcmp(&aitv.it_value, &ctv, <))
  438                                 timevalclear(&aitv.it_value);
  439                         else
  440                                 timevalsub(&aitv.it_value, &ctv);
  441                 }
  442         } else {
  443                 mtx_lock_spin(&sched_lock);
  444                 aitv = p->p_stats->p_timer[uap->which];
  445                 mtx_unlock_spin(&sched_lock);
  446         }
  447         return (copyout(&aitv, uap->itv, sizeof (struct itimerval)));
  448 }
  449 
  450 #ifndef _SYS_SYSPROTO_H_
  451 struct setitimer_args {
  452         u_int   which;
  453         struct  itimerval *itv, *oitv;
  454 };
  455 #endif
  456 /*
  457  * MPSAFE
  458  */
  459 int
  460 setitimer(struct thread *td, struct setitimer_args *uap)
  461 {
  462         struct proc *p = td->td_proc;
  463         struct itimerval aitv, oitv;
  464         struct timeval ctv;
  465         int error;
  466 
  467         if (uap->itv == NULL) {
  468                 uap->itv = uap->oitv;
  469                 return (getitimer(td, (struct getitimer_args *)uap));
  470         }
  471 
  472         if (uap->which > ITIMER_PROF)
  473                 return (EINVAL);
  474         if ((error = copyin(uap->itv, &aitv, sizeof(struct itimerval))))
  475                 return (error);
  476         if (itimerfix(&aitv.it_value))
  477                 return (EINVAL);
  478         if (!timevalisset(&aitv.it_value))
  479                 timevalclear(&aitv.it_interval);
  480         else if (itimerfix(&aitv.it_interval))
  481                 return (EINVAL);
  482 
  483         if (uap->which == ITIMER_REAL) {
  484                 PROC_LOCK(p);
  485                 if (timevalisset(&p->p_realtimer.it_value))
  486                         callout_stop(&p->p_itcallout);
  487                 getmicrouptime(&ctv);
  488                 if (timevalisset(&aitv.it_value)) {
  489                         callout_reset(&p->p_itcallout, tvtohz(&aitv.it_value),
  490                             realitexpire, p);
  491                         timevaladd(&aitv.it_value, &ctv);
  492                 }
  493                 oitv = p->p_realtimer;
  494                 p->p_realtimer = aitv;
  495                 PROC_UNLOCK(p);
  496                 if (timevalisset(&oitv.it_value)) {
  497                         if (timevalcmp(&oitv.it_value, &ctv, <))
  498                                 timevalclear(&oitv.it_value);
  499                         else
  500                                 timevalsub(&oitv.it_value, &ctv);
  501                 }
  502         } else {
  503                 mtx_lock_spin(&sched_lock);
  504                 oitv = p->p_stats->p_timer[uap->which];
  505                 p->p_stats->p_timer[uap->which] = aitv;
  506                 mtx_unlock_spin(&sched_lock);
  507         }
  508         if (uap->oitv == NULL)
  509                 return (0);
  510         return (copyout(&oitv, uap->oitv, sizeof(struct itimerval)));
  511 }
  512 
  513 /*
  514  * Real interval timer expired:
  515  * send process whose timer expired an alarm signal.
  516  * If time is not set up to reload, then just return.
  517  * Else compute next time timer should go off which is > current time.
  518  * This is where delay in processing this timeout causes multiple
  519  * SIGALRM calls to be compressed into one.
  520  * tvtohz() always adds 1 to allow for the time until the next clock
  521  * interrupt being strictly less than 1 clock tick, but we don't want
  522  * that here since we want to appear to be in sync with the clock
  523  * interrupt even when we're delayed.
  524  */
  525 void
  526 realitexpire(void *arg)
  527 {
  528         struct proc *p;
  529         struct timeval ctv, ntv;
  530 
  531         p = (struct proc *)arg;
  532         PROC_LOCK(p);
  533         psignal(p, SIGALRM);
  534         if (!timevalisset(&p->p_realtimer.it_interval)) {
  535                 timevalclear(&p->p_realtimer.it_value);
  536                 if (p->p_flag & P_WEXIT)
  537                         wakeup(&p->p_itcallout);
  538                 PROC_UNLOCK(p);
  539                 return;
  540         }
  541         for (;;) {
  542                 timevaladd(&p->p_realtimer.it_value,
  543                     &p->p_realtimer.it_interval);
  544                 getmicrouptime(&ctv);
  545                 if (timevalcmp(&p->p_realtimer.it_value, &ctv, >)) {
  546                         ntv = p->p_realtimer.it_value;
  547                         timevalsub(&ntv, &ctv);
  548                         callout_reset(&p->p_itcallout, tvtohz(&ntv) - 1,
  549                             realitexpire, p);
  550                         PROC_UNLOCK(p);
  551                         return;
  552                 }
  553         }
  554         /*NOTREACHED*/
  555 }
  556 
  557 /*
  558  * Check that a proposed value to load into the .it_value or
  559  * .it_interval part of an interval timer is acceptable, and
  560  * fix it to have at least minimal value (i.e. if it is less
  561  * than the resolution of the clock, round it up.)
  562  */
  563 int
  564 itimerfix(struct timeval *tv)
  565 {
  566 
  567         if (tv->tv_sec < 0 || tv->tv_sec > 100000000 ||
  568             tv->tv_usec < 0 || tv->tv_usec >= 1000000)
  569                 return (EINVAL);
  570         if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
  571                 tv->tv_usec = tick;
  572         return (0);
  573 }
  574 
  575 /*
  576  * Decrement an interval timer by a specified number
  577  * of microseconds, which must be less than a second,
  578  * i.e. < 1000000.  If the timer expires, then reload
  579  * it.  In this case, carry over (usec - old value) to
  580  * reduce the value reloaded into the timer so that
  581  * the timer does not drift.  This routine assumes
  582  * that it is called in a context where the timers
  583  * on which it is operating cannot change in value.
  584  */
  585 int
  586 itimerdecr(struct itimerval *itp, int usec)
  587 {
  588 
  589         if (itp->it_value.tv_usec < usec) {
  590                 if (itp->it_value.tv_sec == 0) {
  591                         /* expired, and already in next interval */
  592                         usec -= itp->it_value.tv_usec;
  593                         goto expire;
  594                 }
  595                 itp->it_value.tv_usec += 1000000;
  596                 itp->it_value.tv_sec--;
  597         }
  598         itp->it_value.tv_usec -= usec;
  599         usec = 0;
  600         if (timevalisset(&itp->it_value))
  601                 return (1);
  602         /* expired, exactly at end of interval */
  603 expire:
  604         if (timevalisset(&itp->it_interval)) {
  605                 itp->it_value = itp->it_interval;
  606                 itp->it_value.tv_usec -= usec;
  607                 if (itp->it_value.tv_usec < 0) {
  608                         itp->it_value.tv_usec += 1000000;
  609                         itp->it_value.tv_sec--;
  610                 }
  611         } else
  612                 itp->it_value.tv_usec = 0;              /* sec is already 0 */
  613         return (0);
  614 }
  615 
  616 /*
  617  * Add and subtract routines for timevals.
  618  * N.B.: subtract routine doesn't deal with
  619  * results which are before the beginning,
  620  * it just gets very confused in this case.
  621  * Caveat emptor.
  622  */
  623 void
  624 timevaladd(struct timeval *t1, const struct timeval *t2)
  625 {
  626 
  627         t1->tv_sec += t2->tv_sec;
  628         t1->tv_usec += t2->tv_usec;
  629         timevalfix(t1);
  630 }
  631 
  632 void
  633 timevalsub(struct timeval *t1, const struct timeval *t2)
  634 {
  635 
  636         t1->tv_sec -= t2->tv_sec;
  637         t1->tv_usec -= t2->tv_usec;
  638         timevalfix(t1);
  639 }
  640 
  641 static void
  642 timevalfix(struct timeval *t1)
  643 {
  644 
  645         if (t1->tv_usec < 0) {
  646                 t1->tv_sec--;
  647                 t1->tv_usec += 1000000;
  648         }
  649         if (t1->tv_usec >= 1000000) {
  650                 t1->tv_sec++;
  651                 t1->tv_usec -= 1000000;
  652         }
  653 }
  654 
  655 /*
  656  * ratecheck(): simple time-based rate-limit checking.
  657  */
  658 int
  659 ratecheck(struct timeval *lasttime, const struct timeval *mininterval)
  660 {
  661         struct timeval tv, delta;
  662         int rv = 0;
  663 
  664         getmicrouptime(&tv);            /* NB: 10ms precision */
  665         delta = tv;
  666         timevalsub(&delta, lasttime);
  667 
  668         /*
  669          * check for 0,0 is so that the message will be seen at least once,
  670          * even if interval is huge.
  671          */
  672         if (timevalcmp(&delta, mininterval, >=) ||
  673             (lasttime->tv_sec == 0 && lasttime->tv_usec == 0)) {
  674                 *lasttime = tv;
  675                 rv = 1;
  676         }
  677 
  678         return (rv);
  679 }
  680 
  681 /*
  682  * ppsratecheck(): packets (or events) per second limitation.
  683  *
  684  * Return 0 if the limit is to be enforced (e.g. the caller
  685  * should drop a packet because of the rate limitation).
  686  *
  687  * maxpps of 0 always causes zero to be returned.  maxpps of -1
  688  * always causes 1 to be returned; this effectively defeats rate
  689  * limiting.
  690  *
  691  * Note that we maintain the struct timeval for compatibility
  692  * with other bsd systems.  We reuse the storage and just monitor
  693  * clock ticks for minimal overhead.  
  694  */
  695 int
  696 ppsratecheck(struct timeval *lasttime, int *curpps, int maxpps)
  697 {
  698         int now;
  699 
  700         /*
  701          * Reset the last time and counter if this is the first call
  702          * or more than a second has passed since the last update of
  703          * lasttime.
  704          */
  705         now = ticks;
  706         if (lasttime->tv_sec == 0 || (u_int)(now - lasttime->tv_sec) >= hz) {
  707                 lasttime->tv_sec = now;
  708                 *curpps = 1;
  709                 return (maxpps != 0);
  710         } else {
  711                 (*curpps)++;            /* NB: ignore potential overflow */
  712                 return (maxpps < 0 || *curpps < maxpps);
  713         }
  714 }
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_time.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_time.c
