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Fix monotonic interval timers.

/*	$NetBSD: subr_time.c,v 1.9 2011/12/18 22:30:25 christos Exp $	*/

/*
 * 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. 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_clock.c	8.5 (Berkeley) 1/21/94
 *	@(#)kern_time.c 8.4 (Berkeley) 5/26/95
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_time.c,v 1.9 2011/12/18 22:30:25 christos Exp $");

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/timex.h>
#include <sys/time.h>
#include <sys/timetc.h>
#include <sys/intr.h>

/*
 * Compute number of hz until specified time.  Used to compute second
 * argument to callout_reset() from an absolute time.
 */
int
tvhzto(const struct timeval *tvp)
{
	struct timeval now, tv;

	tv = *tvp;	/* Don't modify original tvp. */
	getmicrotime(&now);
	timersub(&tv, &now, &tv);
	return tvtohz(&tv);
}

/*
 * Compute number of ticks in the specified amount of time.
 */
int
tvtohz(const struct timeval *tv)
{
	unsigned long ticks;
	long sec, usec;

	/*
	 * If the number of usecs in the whole seconds part of the time
	 * difference fits in a long, then the total number of usecs will
	 * fit in an unsigned long.  Compute the total and convert it to
	 * ticks, rounding up and adding 1 to allow for the current tick
	 * to expire.  Rounding also depends on unsigned long arithmetic
	 * to avoid overflow.
	 *
	 * Otherwise, if the number of ticks in the whole seconds part of
	 * the time difference fits in a long, then convert the parts to
	 * ticks separately and add, using similar rounding methods and
	 * overflow avoidance.  This method would work in the previous
	 * case, but it is slightly slower and assumes that hz is integral.
	 *
	 * Otherwise, round the time difference down to the maximum
	 * representable value.
	 *
	 * If ints are 32-bit, then the maximum value for any timeout in
	 * 10ms ticks is 248 days.
	 */
	sec = tv->tv_sec;
	usec = tv->tv_usec;

	KASSERT(usec >= 0 && usec < 1000000);

	/* catch overflows in conversion time_t->int */
	if (tv->tv_sec > INT_MAX)
		return INT_MAX;
	if (tv->tv_sec < 0)
		return 0;

	if (sec < 0 || (sec == 0 && usec == 0)) {
		/*
		 * Would expire now or in the past.  Return 0 ticks.
		 * This is different from the legacy tvhzto() interface,
		 * and callers need to check for it.
		 */
		ticks = 0;
	} else if (sec <= (LONG_MAX / 1000000))
		ticks = (((sec * 1000000) + (unsigned long)usec + (tick - 1))
		    / tick) + 1;
	else if (sec <= (LONG_MAX / hz))
		ticks = (sec * hz) +
		    (((unsigned long)usec + (tick - 1)) / tick) + 1;
	else
		ticks = LONG_MAX;

	if (ticks > INT_MAX)
		ticks = INT_MAX;

	return ((int)ticks);
}

int
tshzto(const struct timespec *tsp)
{
	struct timespec now, ts;

	ts = *tsp;	/* Don't modify original tsp. */
	getnanotime(&now);
	timespecsub(&ts, &now, &ts);
	return tstohz(&ts);
}

int
tshztoup(const struct timespec *tsp)
{
	struct timespec now, ts;

	ts = *tsp;	/* Don't modify original tsp. */
	getnanouptime(&now);
	timespecsub(&ts, &now, &ts);
	return tstohz(&ts);
}

/*
 * Compute number of ticks in the specified amount of time.
 */
int
tstohz(const struct timespec *ts)
{
	struct timeval tv;

	/*
	 * usec has great enough resolution for hz, so convert to a
	 * timeval and use tvtohz() above.
	 */
	TIMESPEC_TO_TIMEVAL(&tv, ts);
	return tvtohz(&tv);
}

/*
 * 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(struct timeval *tv)
{

	if (tv->tv_sec < 0 || 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);
}

int
itimespecfix(struct timespec *ts)
{

	if (ts->tv_sec < 0 || ts->tv_nsec < 0 || ts->tv_nsec >= 1000000000)
		return (EINVAL);
	if (ts->tv_sec == 0 && ts->tv_nsec != 0 && ts->tv_nsec < tick * 1000)
		ts->tv_nsec = tick * 1000;
	return (0);
}

int
inittimeleft(struct timespec *ts, struct timespec *sleepts)
{

	if (itimespecfix(ts)) {
		return -1;
	}
	getnanouptime(sleepts);
	return 0;
}

int
gettimeleft(struct timespec *ts, struct timespec *sleepts)
{
	struct timespec sleptts;

	/*
	 * Reduce ts by elapsed time based on monotonic time scale.
	 */
	getnanouptime(&sleptts);
	timespecadd(ts, sleepts, ts);
	timespecsub(ts, &sleptts, ts);
	*sleepts = sleptts;

	return tstohz(ts);
}

/*
 * Calculate delta and convert from struct timespec to the ticks.
 */
int
abstimeout2timo(struct timespec *ts, int *timo)
{
	struct timespec tsd;
	int error;

	getnanotime(&tsd);
	timespecsub(ts, &tsd, &tsd);
	if (tsd.tv_sec < 0 || (tsd.tv_sec == 0 && tsd.tv_nsec <= 0)) {
		return ETIMEDOUT;
	}
	error = itimespecfix(&tsd);
	if (error) {
		return error;
	}
	*timo = tstohz(&tsd);
	KASSERT(*timo != 0);

	return 0;
}