[unix-history] / sys / kern / kern_time.c

/*
 * Copyright (c) 1982, 1986, 1989 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	7.15 (Berkeley) 3/17/91
 */

#include "param.h"
#include "resourcevar.h"
#include "kernel.h"
#include "proc.h"

#include "machine/cpu.h"

/* 
 * 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.
 */

/* ARGSUSED */
gettimeofday(p, uap, retval)
	struct proc *p;
	register struct args {
		struct	timeval *tp;
		struct	timezone *tzp;
	} *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);
}

/* ARGSUSED */
settimeofday(p, uap, retval)
	struct proc *p;
	struct args {
		struct	timeval *tv;
		struct	timezone *tzp;
	} *uap;
	int *retval;
{
	struct timeval atv;
	struct timezone atz;
	int error, s;

	if (error = suser(p->p_ucred, &p->p_acflag))
		return (error);
	if (uap->tv) {
		if (error = copyin((caddr_t)uap->tv, (caddr_t)&atv,
		    sizeof (struct timeval)))
			return (error);
		/* WHAT DO WE DO ABOUT PENDING REAL-TIME TIMEOUTS??? */
		boottime.tv_sec += atv.tv_sec - time.tv_sec;
		s = splhigh(); time = atv; splx(s);
		resettodr();
	}
	if (uap->tzp && (error = copyin((caddr_t)uap->tzp, (caddr_t)&atz,
	    sizeof (atz))) == 0)
		tz = atz;
	return (error);
}

extern	int tickadj;			/* "standard" clock skew, us./tick */
int	tickdelta;			/* current clock skew, us. per tick */
long	timedelta;			/* unapplied time correction, us. */
long	bigadj = 1000000;		/* use 10x skew above bigadj us. */

/* ARGSUSED */
adjtime(p, uap, retval)
	struct proc *p;
	register struct args {
		struct timeval *delta;
		struct timeval *olddelta;
	} *uap;
	int *retval;
{
	struct timeval atv, oatv;
	register long ndelta;
	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);
	ndelta = atv.tv_sec * 1000000 + atv.tv_usec;
	if (timedelta == 0)
		if (ndelta > bigadj)
			tickdelta = 10 * tickadj;
		else
			tickdelta = tickadj;
	if (ndelta % tickdelta)
		ndelta = ndelta / tickadj * tickadj;

	s = splclock();
	if (uap->olddelta) {
		oatv.tv_sec = timedelta / 1000000;
		oatv.tv_usec = timedelta % 1000000;
	}
	timedelta = ndelta;
	splx(s);

	if (uap->olddelta)
		(void) copyout((caddr_t)&oatv, (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.
 */
/* ARGSUSED */
getitimer(p, uap, retval)
	struct proc *p;
	register struct args {
		u_int	which;
		struct	itimerval *itv;
	} *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, &time);
	} else
		aitv = p->p_stats->p_timer[uap->which];
	splx(s);
	return (copyout((caddr_t)&aitv, (caddr_t)uap->itv,
	    sizeof (struct itimerval)));
}

/* ARGSUSED */
setitimer(p, uap, retval)
	struct proc *p;
	register struct args {
		u_int	which;
		struct	itimerval *itv, *oitv;
	} *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, 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, &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.
 */
realitexpire(p)
	register struct proc *p;
{
	int s;

	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));
			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.)
 */
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
 * reducint 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.
 */
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.
 */
timevaladd(t1, t2)
	struct timeval *t1, *t2;
{

	t1->tv_sec += t2->tv_sec;
	t1->tv_usec += t2->tv_usec;
	timevalfix(t1);
}

timevalsub(t1, t2)
	struct timeval *t1, *t2;
{

	t1->tv_sec -= t2->tv_sec;
	t1->tv_usec -= t2->tv_usec;
	timevalfix(t1);
}

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;
	}
}
Commit	Line	Data
15637ed4 RG	1	/*
	2	* Copyright (c) 1982, 1986, 1989 Regents of the University of California.
	3	* 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 7.15 (Berkeley) 3/17/91
	34	*/
	35
	36	#include "param.h"
	37	#include "resourcevar.h"
	38	#include "kernel.h"
	39	#include "proc.h"
	40
	41	#include "machine/cpu.h"
	42
	43	/*
	44	* Time of day and interval timer support.
	45	*
	46	* These routines provide the kernel entry points to get and set
	47	* the time-of-day and per-process interval timers. Subroutines
	48	* here provide support for adding and subtracting timeval structures
	49	* and decrementing interval timers, optionally reloading the interval
	50	* timers when they expire.
	51	*/
	52
	53	/* ARGSUSED */
	54	gettimeofday(p, uap, retval)
	55	struct proc *p;
	56	register struct args {
	57	struct timeval *tp;
	58	struct timezone *tzp;
	59	} *uap;
	60	int *retval;
	61	{
	62	struct timeval atv;
	63	int error = 0;
	64
65	if (uap->tp) {
66	microtime(&atv);
67	if (error = copyout((caddr_t)&atv, (caddr_t)uap->tp,
68	sizeof (atv)))
69	return (error);
70	}
71	if (uap->tzp)
72	error = copyout((caddr_t)&tz, (caddr_t)uap->tzp,
73	sizeof (tz));
74	return (error);
75	}
76
77	/* ARGSUSED */
78	settimeofday(p, uap, retval)
79	struct proc *p;
80	struct args {
81	struct timeval *tv;
82	struct timezone *tzp;
83	} *uap;
84	int *retval;
85	{
86	struct timeval atv;
87	struct timezone atz;
88	int error, s;
89
90	if (error = suser(p->p_ucred, &p->p_acflag))
91	return (error);
92	if (uap->tv) {
93	if (error = copyin((caddr_t)uap->tv, (caddr_t)&atv,
94	sizeof (struct timeval)))
95	return (error);
96	/* WHAT DO WE DO ABOUT PENDING REAL-TIME TIMEOUTS??? */
97	boottime.tv_sec += atv.tv_sec - time.tv_sec;
98	s = splhigh(); time = atv; splx(s);
99	resettodr();
100	}
101	if (uap->tzp && (error = copyin((caddr_t)uap->tzp, (caddr_t)&atz,
102	sizeof (atz))) == 0)
103	tz = atz;
104	return (error);
105	}
106
107	extern int tickadj; /* "standard" clock skew, us./tick */
108	int tickdelta; /* current clock skew, us. per tick */
109	long timedelta; /* unapplied time correction, us. */
110	long bigadj = 1000000; /* use 10x skew above bigadj us. */
111
112	/* ARGSUSED */
113	adjtime(p, uap, retval)
114	struct proc *p;
115	register struct args {
116	struct timeval *delta;
117	struct timeval *olddelta;
118	} *uap;
119	int *retval;
120	{
121	struct timeval atv, oatv;
122	register long ndelta;
123	int s, error;
124
125	if (error = suser(p->p_ucred, &p->p_acflag))
126	return (error);
127	if (error =
128	copyin((caddr_t)uap->delta, (caddr_t)&atv, sizeof (struct timeval)))
129	return (error);
130	ndelta = atv.tv_sec * 1000000 + atv.tv_usec;
131	if (timedelta == 0)
132	if (ndelta > bigadj)
133	tickdelta = 10 * tickadj;
134	else
135	tickdelta = tickadj;
136	if (ndelta % tickdelta)
137	ndelta = ndelta / tickadj * tickadj;
138
139	s = splclock();
140	if (uap->olddelta) {
141	oatv.tv_sec = timedelta / 1000000;
142	oatv.tv_usec = timedelta % 1000000;
143	}
144	timedelta = ndelta;
145	splx(s);
146
147	if (uap->olddelta)
148	(void) copyout((caddr_t)&oatv, (caddr_t)uap->olddelta,
149	sizeof (struct timeval));
150	return (0);
151	}
152
153	/*
154	* Get value of an interval timer. The process virtual and
155	* profiling virtual time timers are kept in the p_stats area, since
156	* they can be swapped out. These are kept internally in the
157	* way they are specified externally: in time until they expire.
158	*
159	* The real time interval timer is kept in the process table slot
160	* for the process, and its value (it_value) is kept as an
161	* absolute time rather than as a delta, so that it is easy to keep
162	* periodic real-time signals from drifting.
163	*
164	* Virtual time timers are processed in the hardclock() routine of
165	* kern_clock.c. The real time timer is processed by a timeout
166	* routine, called from the softclock() routine. Since a callout
167	* may be delayed in real time due to interrupt processing in the system,
168	* it is possible for the real time timeout routine (realitexpire, given below),
169	* to be delayed in real time past when it is supposed to occur. It
170	* does not suffice, therefore, to reload the real timer .it_value from the
171	* real time timers .it_interval. Rather, we compute the next time in
172	* absolute time the timer should go off.
173	*/
174	/* ARGSUSED */
175	getitimer(p, uap, retval)
176	struct proc *p;
177	register struct args {
178	u_int which;
179	struct itimerval *itv;
180	} *uap;
181	int *retval;
182	{
183	struct itimerval aitv;
184	int s;
185
186	if (uap->which > ITIMER_PROF)
187	return (EINVAL);
188	s = splclock();
189	if (uap->which == ITIMER_REAL) {
190	/*
191	* Convert from absoulte to relative time in .it_value
192	* part of real time timer. If time for real time timer
193	* has passed return 0, else return difference between
194	* current time and time for the timer to go off.
195	*/
196	aitv = p->p_realtimer;
197	if (timerisset(&aitv.it_value))
198	if (timercmp(&aitv.it_value, &time, <))
199	timerclear(&aitv.it_value);
200	else
201	timevalsub(&aitv.it_value, &time);
202	} else
203	aitv = p->p_stats->p_timer[uap->which];
204	splx(s);
205	return (copyout((caddr_t)&aitv, (caddr_t)uap->itv,
206	sizeof (struct itimerval)));
207	}
208
209	/* ARGSUSED */
210	setitimer(p, uap, retval)
211	struct proc *p;
212	register struct args {
213	u_int which;
214	struct itimerval itv, oitv;
215	} *uap;
216	int *retval;
217	{
218	struct itimerval aitv;
219	register struct itimerval *itvp;
220	int s, error;
221
222	if (uap->which > ITIMER_PROF)
223	return (EINVAL);
224	itvp = uap->itv;
225	if (itvp && (error = copyin((caddr_t)itvp, (caddr_t)&aitv,
226	sizeof(struct itimerval))))
227	return (error);
228	if ((uap->itv = uap->oitv) && (error = getitimer(p, uap, retval)))
229	return (error);
230	if (itvp == 0)
231	return (0);
232	if (itimerfix(&aitv.it_value) \|\| itimerfix(&aitv.it_interval))
233	return (EINVAL);
234	s = splclock();
235	if (uap->which == ITIMER_REAL) {
236	untimeout(realitexpire, (caddr_t)p);
237	if (timerisset(&aitv.it_value)) {
238	timevaladd(&aitv.it_value, &time);
239	timeout(realitexpire, (caddr_t)p, hzto(&aitv.it_value));
240	}
241	p->p_realtimer = aitv;
242	} else
243	p->p_stats->p_timer[uap->which] = aitv;
244	splx(s);
245	return (0);
246	}
247
248	/*
249	* Real interval timer expired:
250	* send process whose timer expired an alarm signal.
251	* If time is not set up to reload, then just return.
252	* Else compute next time timer should go off which is > current time.
253	* This is where delay in processing this timeout causes multiple
254	* SIGALRM calls to be compressed into one.
255	*/
256	realitexpire(p)
257	register struct proc *p;
258	{
259	int s;
260
261	psignal(p, SIGALRM);
262	if (!timerisset(&p->p_realtimer.it_interval)) {
263	timerclear(&p->p_realtimer.it_value);
264	return;
265	}
266	for (;;) {
267	s = splclock();
268	timevaladd(&p->p_realtimer.it_value,
269	&p->p_realtimer.it_interval);
270	if (timercmp(&p->p_realtimer.it_value, &time, >)) {
271	timeout(realitexpire, (caddr_t)p,
272	hzto(&p->p_realtimer.it_value));
273	splx(s);
274	return;
275	}
276	splx(s);
277	}
278	}
279
280	/*
281	* Check that a proposed value to load into the .it_value or
282	* .it_interval part of an interval timer is acceptable, and
283	* fix it to have at least minimal value (i.e. if it is less
284	* than the resolution of the clock, round it up.)
285	*/
286	itimerfix(tv)
287	struct timeval *tv;
288	{
289
290	if (tv->tv_sec < 0 \|\| tv->tv_sec > 100000000 \|\|
291	tv->tv_usec < 0 \|\| tv->tv_usec >= 1000000)
292	return (EINVAL);
293	if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
294	tv->tv_usec = tick;
295	return (0);
296	}
297
298	/*
299	* Decrement an interval timer by a specified number
300	* of microseconds, which must be less than a second,
301	* i.e. < 1000000. If the timer expires, then reload
302	* it. In this case, carry over (usec - old value) to
303	* reducint the value reloaded into the timer so that
304	* the timer does not drift. This routine assumes
305	* that it is called in a context where the timers
306	* on which it is operating cannot change in value.
307	*/
308	itimerdecr(itp, usec)
309	register struct itimerval *itp;
310	int usec;
311	{
312
313	if (itp->it_value.tv_usec < usec) {
314	if (itp->it_value.tv_sec == 0) {
315	/* expired, and already in next interval */
316	usec -= itp->it_value.tv_usec;
317	goto expire;
318	}
319	itp->it_value.tv_usec += 1000000;
320	itp->it_value.tv_sec--;
321	}
322	itp->it_value.tv_usec -= usec;
323	usec = 0;
324	if (timerisset(&itp->it_value))
325	return (1);
326	/* expired, exactly at end of interval */
327	expire:
328	if (timerisset(&itp->it_interval)) {
329	itp->it_value = itp->it_interval;
330	itp->it_value.tv_usec -= usec;
331	if (itp->it_value.tv_usec < 0) {
332	itp->it_value.tv_usec += 1000000;
333	itp->it_value.tv_sec--;
334	}
335	} else
336	itp->it_value.tv_usec = 0; /* sec is already 0 */
337	return (0);
338	}
339
340	/*
341	* Add and subtract routines for timevals.
342	* N.B.: subtract routine doesn't deal with
343	* results which are before the beginning,
344	* it just gets very confused in this case.
345	* Caveat emptor.
346	*/
347	timevaladd(t1, t2)
348	struct timeval t1, t2;
349	{
350
351	t1->tv_sec += t2->tv_sec;
352	t1->tv_usec += t2->tv_usec;
353	timevalfix(t1);
354	}
355
356	timevalsub(t1, t2)
357	struct timeval t1, t2;
358	{
359
360	t1->tv_sec -= t2->tv_sec;
361	t1->tv_usec -= t2->tv_usec;
362	timevalfix(t1);
363	}
364
365	timevalfix(t1)
366	struct timeval *t1;
367	{
368
369	if (t1->tv_usec < 0) {
370	t1->tv_sec--;
371	t1->tv_usec += 1000000;
372	}
373	if (t1->tv_usec >= 1000000) {
374	t1->tv_sec++;
375	t1->tv_usec -= 1000000;
376	}
377	}