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

     /*
      * Copyright (c) 1982, 1986, 1989, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)kern_time.c 8.1 (Berkeley) 6/10/93
     * $FreeBSD: src/sys/kern/kern_time.c,v 1.18.2.3 1999/09/05 08:15:07 peter Exp $
     */
    
    #include <sys/param.h>
    #include <sys/sysproto.h>
    #include <sys/resourcevar.h>
    #include <sys/signalvar.h>
    #include <sys/kernel.h>
    #include <sys/systm.h>
    #include <sys/proc.h>
    #include <sys/vnode.h>
    
    struct timezone tz;
    
    /*
     * Time of day and interval timer support.
     *
     * These routines provide the kernel entry points to get and set
     * the time-of-day and per-process interval timers.  Subroutines
     * here provide support for adding and subtracting timeval structures
     * and decrementing interval timers, optionally reloading the interval
     * timers when they expire.
     */
    
    static void     timevalfix __P((struct timeval *));
    
    #ifndef _SYS_SYSPROTO_H_
    struct gettimeofday_args {
            struct  timeval *tp;
            struct  timezone *tzp;
    };
    #endif
    /* ARGSUSED */
    int
    gettimeofday(p, uap, retval)
            struct proc *p;
            register struct gettimeofday_args *uap;
            int *retval;
    {
            struct timeval atv;
            int error = 0;
    
            if (uap->tp) {
                    microtime(&atv);
                    if ((error = copyout((caddr_t)&atv, (caddr_t)uap->tp,
                        sizeof (atv))))
                            return (error);
            }
            if (uap->tzp)
                    error = copyout((caddr_t)&tz, (caddr_t)uap->tzp,
                        sizeof (tz));
            return (error);
    }
    
    #ifndef _SYS_SYSPROTO_H_
    struct settimeofday_args {
            struct  timeval *tv;
            struct  timezone *tzp;
    };
    #endif
    /* ARGSUSED */
    int
    settimeofday(p, uap, retval)
            struct proc *p;
            struct settimeofday_args *uap;
            int *retval;
   {
           struct timeval atv, delta;
           struct timezone atz;
           int error, s;
   
           if ((error = suser(p->p_ucred, &p->p_acflag)))
                   return (error);
           /* Verify all parameters before changing time. */
           if (uap->tv &&
               (error = copyin((caddr_t)uap->tv, (caddr_t)&atv, sizeof(atv))))
                   return (error);
           if (atv.tv_usec < 0 || atv.tv_usec >= 1000000)
                   return (EINVAL);
           if (uap->tzp &&
               (error = copyin((caddr_t)uap->tzp, (caddr_t)&atz, sizeof(atz))))
                   return (error);
           if (uap->tv) {
                   s = splclock();
                   /*
                    * Calculate delta directly to minimize clock interrupt
                    * latency.  Fix it after the ipl has been lowered.
                    */
                   delta.tv_sec = atv.tv_sec - time.tv_sec;
                   delta.tv_usec = atv.tv_usec - time.tv_usec;
                   time = atv;
                   /*
                    * XXX should arrange for microtime() to agree with atv if
                    * it is called now.  As it is, it may add up to about
                    * `tick' unwanted usec.
                    * Another problem is that clock interrupts may occur at
                    * other than multiples of `tick'.  It's not worth fixing
                    * this here, since the problem is also caused by tick
                    * adjustments.
                    */
                   (void) splsoftclock();
                   timevalfix(&delta);
                   timevaladd(&boottime, &delta);
                   timevaladd(&runtime, &delta);
                   /* re-use 'p' */
                   for (p = allproc.lh_first; p != 0; p = p->p_list.le_next)
                           if (timerisset(&p->p_realtimer.it_value))
                                   timevaladd(&p->p_realtimer.it_value, &delta);
                   LEASE_UPDATETIME(delta.tv_sec);
                   splx(s);
                   resettodr();
           }
           if (uap->tzp)
                   tz = atz;
           return (0);
   }
   
   extern  int tickadj;                    /* "standard" clock skew, us./tick */
   int     tickdelta;                      /* current clock skew, us. per tick */
   long    timedelta;                      /* unapplied time correction, us. */
   static long     bigadj = 1000000;       /* use 10x skew above bigadj us. */
   
   #ifndef _SYS_SYSPROTO_H_
   struct adjtime_args {
           struct timeval *delta;
           struct timeval *olddelta;
   };
   #endif
   /* ARGSUSED */
   int
   adjtime(p, uap, retval)
           struct proc *p;
           register struct adjtime_args *uap;
           int *retval;
   {
           struct timeval atv;
           register long ndelta, ntickdelta, odelta;
           int s, error;
   
           if ((error = suser(p->p_ucred, &p->p_acflag)))
                   return (error);
           if ((error =
               copyin((caddr_t)uap->delta, (caddr_t)&atv, sizeof(struct timeval))))
                   return (error);
   
           /*
            * Compute the total correction and the rate at which to apply it.
            * Round the adjustment down to a whole multiple of the per-tick
            * delta, so that after some number of incremental changes in
            * hardclock(), tickdelta will become zero, lest the correction
            * overshoot and start taking us away from the desired final time.
            */
           ndelta = atv.tv_sec * 1000000 + atv.tv_usec;
           if (ndelta > bigadj || ndelta < -bigadj)
                   ntickdelta = 10 * tickadj;
           else
                   ntickdelta = tickadj;
           if (ndelta % ntickdelta)
                   ndelta = ndelta / ntickdelta * ntickdelta;
   
           /*
            * To make hardclock()'s job easier, make the per-tick delta negative
            * if we want time to run slower; then hardclock can simply compute
            * tick + tickdelta, and subtract tickdelta from timedelta.
            */
           if (ndelta < 0)
                   ntickdelta = -ntickdelta;
           s = splclock();
           odelta = timedelta;
           timedelta = ndelta;
           tickdelta = ntickdelta;
           splx(s);
   
           if (uap->olddelta) {
                   atv.tv_sec = odelta / 1000000;
                   atv.tv_usec = odelta % 1000000;
                   (void) copyout((caddr_t)&atv, (caddr_t)uap->olddelta,
                       sizeof(struct timeval));
           }
           return (0);
   }
   
   /*
    * Get value of an interval timer.  The process virtual and
    * profiling virtual time timers are kept in the p_stats area, since
    * they can be swapped out.  These are kept internally in the
    * way they are specified externally: in time until they expire.
    *
    * The real time interval timer is kept in the process table slot
    * for the process, and its value (it_value) is kept as an
    * absolute time rather than as a delta, so that it is easy to keep
    * periodic real-time signals from drifting.
    *
    * Virtual time timers are processed in the hardclock() routine of
    * kern_clock.c.  The real time timer is processed by a timeout
    * routine, called from the softclock() routine.  Since a callout
    * may be delayed in real time due to interrupt processing in the system,
    * it is possible for the real time timeout routine (realitexpire, given below),
    * to be delayed in real time past when it is supposed to occur.  It
    * does not suffice, therefore, to reload the real timer .it_value from the
    * real time timers .it_interval.  Rather, we compute the next time in
    * absolute time the timer should go off.
    */
   #ifndef _SYS_SYSPROTO_H_
   struct getitimer_args {
           u_int   which;
           struct  itimerval *itv;
   };
   #endif
   /* ARGSUSED */
   int
   getitimer(p, uap, retval)
           struct proc *p;
           register struct getitimer_args *uap;
           int *retval;
   {
           struct itimerval aitv;
           int s;
   
           if (uap->which > ITIMER_PROF)
                   return (EINVAL);
           s = splclock();
           if (uap->which == ITIMER_REAL) {
                   /*
                    * Convert from absoulte to relative time in .it_value
                    * part of real time timer.  If time for real time timer
                    * has passed return 0, else return difference between
                    * current time and time for the timer to go off.
                    */
                   aitv = p->p_realtimer;
                   if (timerisset(&aitv.it_value))
                           if (timercmp(&aitv.it_value, &time, <))
                                   timerclear(&aitv.it_value);
                           else
                                   timevalsub(&aitv.it_value,
                                       (struct timeval *)&time);
           } else
                   aitv = p->p_stats->p_timer[uap->which];
           splx(s);
           return (copyout((caddr_t)&aitv, (caddr_t)uap->itv,
               sizeof (struct itimerval)));
   }
   
   #ifndef _SYS_SYSPROTO_H_
   struct setitimer_args {
           u_int   which;
           struct  itimerval *itv, *oitv;
   };
   #endif
   /* ARGSUSED */
   int
   setitimer(p, uap, retval)
           struct proc *p;
           register struct setitimer_args *uap;
           int *retval;
   {
           struct itimerval aitv;
           register struct itimerval *itvp;
           int s, error;
   
           if (uap->which > ITIMER_PROF)
                   return (EINVAL);
           itvp = uap->itv;
           if (itvp && (error = copyin((caddr_t)itvp, (caddr_t)&aitv,
               sizeof(struct itimerval))))
                   return (error);
           if ((uap->itv = uap->oitv) &&
               (error = getitimer(p, (struct getitimer_args *)uap, retval)))
                   return (error);
           if (itvp == 0)
                   return (0);
           if (itimerfix(&aitv.it_value) || itimerfix(&aitv.it_interval))
                   return (EINVAL);
           s = splclock();
           if (uap->which == ITIMER_REAL) {
                   untimeout(realitexpire, (caddr_t)p);
                   if (timerisset(&aitv.it_value)) {
                           timevaladd(&aitv.it_value, (struct timeval *)&time);
                           timeout(realitexpire, (caddr_t)p, hzto(&aitv.it_value));
                   }
                   p->p_realtimer = aitv;
           } else
                   p->p_stats->p_timer[uap->which] = aitv;
           splx(s);
           return (0);
   }
   
   /*
    * Real interval timer expired:
    * send process whose timer expired an alarm signal.
    * If time is not set up to reload, then just return.
    * Else compute next time timer should go off which is > current time.
    * This is where delay in processing this timeout causes multiple
    * SIGALRM calls to be compressed into one.
    * hzto() always adds 1 to allow for the time until the next clock
    * interrupt being strictly less than 1 clock tick, but we don't want
    * that here since we want to appear to be in sync with the clock
    * interrupt even when we're delayed.
    */
   void
   realitexpire(arg)
           void *arg;
   {
           register struct proc *p;
           int s;
   
           p = (struct proc *)arg;
           psignal(p, SIGALRM);
           if (!timerisset(&p->p_realtimer.it_interval)) {
                   timerclear(&p->p_realtimer.it_value);
                   return;
           }
           for (;;) {
                   s = splclock();
                   timevaladd(&p->p_realtimer.it_value,
                       &p->p_realtimer.it_interval);
                   if (timercmp(&p->p_realtimer.it_value, &time, >)) {
                           timeout(realitexpire, (caddr_t)p,
                               hzto(&p->p_realtimer.it_value) - 1);
                           splx(s);
                           return;
                   }
                   splx(s);
           }
   }
   
   /*
    * Check that a proposed value to load into the .it_value or
    * .it_interval part of an interval timer is acceptable, and
    * fix it to have at least minimal value (i.e. if it is less
    * than the resolution of the clock, round it up.)
    */
   int
   itimerfix(tv)
           struct timeval *tv;
   {
   
           if (tv->tv_sec < 0 || tv->tv_sec > 100000000 ||
               tv->tv_usec < 0 || tv->tv_usec >= 1000000)
                   return (EINVAL);
           if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
                   tv->tv_usec = tick;
           return (0);
   }
   
   /*
    * Decrement an interval timer by a specified number
    * of microseconds, which must be less than a second,
    * i.e. < 1000000.  If the timer expires, then reload
    * it.  In this case, carry over (usec - old value) to
    * reduce the value reloaded into the timer so that
    * the timer does not drift.  This routine assumes
    * that it is called in a context where the timers
    * on which it is operating cannot change in value.
    */
   int
   itimerdecr(itp, usec)
           register struct itimerval *itp;
           int usec;
   {
   
           if (itp->it_value.tv_usec < usec) {
                   if (itp->it_value.tv_sec == 0) {
                           /* expired, and already in next interval */
                           usec -= itp->it_value.tv_usec;
                           goto expire;
                   }
                   itp->it_value.tv_usec += 1000000;
                   itp->it_value.tv_sec--;
           }
           itp->it_value.tv_usec -= usec;
           usec = 0;
           if (timerisset(&itp->it_value))
                   return (1);
           /* expired, exactly at end of interval */
   expire:
           if (timerisset(&itp->it_interval)) {
                   itp->it_value = itp->it_interval;
                   itp->it_value.tv_usec -= usec;
                   if (itp->it_value.tv_usec < 0) {
                           itp->it_value.tv_usec += 1000000;
                           itp->it_value.tv_sec--;
                   }
           } else
                   itp->it_value.tv_usec = 0;              /* sec is already 0 */
           return (0);
   }
   
   /*
    * Add and subtract routines for timevals.
    * N.B.: subtract routine doesn't deal with
    * results which are before the beginning,
    * it just gets very confused in this case.
    * Caveat emptor.
    */
   void
   timevaladd(t1, t2)
           struct timeval *t1, *t2;
   {
   
           t1->tv_sec += t2->tv_sec;
           t1->tv_usec += t2->tv_usec;
           timevalfix(t1);
   }
   
   void
   timevalsub(t1, t2)
           struct timeval *t1, *t2;
   {
   
           t1->tv_sec -= t2->tv_sec;
           t1->tv_usec -= t2->tv_usec;
           timevalfix(t1);
   }
   
   static void
   timevalfix(t1)
           struct timeval *t1;
   {
   
           if (t1->tv_usec < 0) {
                   t1->tv_sec--;
                   t1->tv_usec += 1000000;
           }
           if (t1->tv_usec >= 1000000) {
                   t1->tv_sec++;
                   t1->tv_usec -= 1000000;
           }
   }

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