kern_clock.c

很好的一个嵌入式linux平台下的bootloader

/* $Id: kern_clock.c,v 1.2 1996/01/16 14:21:19 chris Exp $ */
/*-
 * Copyright (c) 1982, 1986, 1991 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_clock.c	7.16 (Berkeley) 5/9/91
 */

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

/*
 * Clock handling routines.
 *
 */

/*
 * Bump a timeval by a small number of usec's.
 */
#define BUMPTIME(t, usec) { \
	register struct timeval *tp = (t); \
 \
	tp->tv_usec += (usec); \
	if (tp->tv_usec >= 1000000) { \
		tp->tv_usec -= 1000000; \
		tp->tv_sec++; \
	} \
}

/*
 * The hz hardware interval timer.
 * We update the events relating to real time.
 * If this timer is also being used to gather statistics,
 * we run through the statistics gathering routine as well.
 */
hardclock(ticks)
{
	register struct callout *p1;
	register struct proc *p;
	register int s;
	int needsoft = 0;

	/*
	 * Update real-time timeout queue.
	 * At front of queue are some number of events which are ``due''.
	 * The time to these is <= 0 and if negative represents the
	 * number of ticks which have passed since it was supposed to happen.
	 * The rest of the q elements (times > 0) are events yet to happen,
	 * where the time for each is given as a delta from the previous.
	 * Decrementing just the first of these serves to decrement the time
	 * to all events.
	 */
	p1 = calltodo.c_next;
	while (p1) {
		if ((p1->c_time -= ticks) > 0)
			break;
		needsoft = 1;
		if (p1->c_time == 0)
			break;
		p1 = p1->c_next;
	}

	if (p = curproc) {
	    struct pstats *pstats = p->p_stats;
	    if (timerisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value) &&
		itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL], ticks*tick) == 0)
	      psignal(p, SIGVTALRM);
	}

	BUMPTIME(&time, ticks * tick)
	if (needsoft)
	  setsoftclock();
}

/*
 * Software priority level clock interrupt.
 * Run periodic events from timeout queue.
 */
/*ARGSUSED*/
softclock()
{
	for (;;) {
		register struct callout *p1;
		register caddr_t arg;
		register int (*func)();
		register int a, s;

		s = splhigh();
		if ((p1 = calltodo.c_next) == 0 || p1->c_time > 0) {
			splx(s);
			break;
		}
		arg = p1->c_arg; func = p1->c_func; a = p1->c_time;
		calltodo.c_next = p1->c_next;
		p1->c_next = callfree;
		callfree = p1;
		splx(s);
		(*func)(arg, a);
	}
}

/*
 * Arrange that (*func)(arg) is called in t/hz seconds.
 */
timeout(func, arg, t)
	int (*func)();
	caddr_t arg;
	register int t;
{
	register struct callout *p1, *p2, *pnew;
	register int s = splhigh();

	if (t <= 0)
		t = 1;
	pnew = callfree;
	if (pnew == NULL)
		panic("timeout table overflow");
	callfree = pnew->c_next;
	pnew->c_arg = arg;
	pnew->c_func = func;
	for (p1 = &calltodo; (p2 = p1->c_next) && p2->c_time < t; p1 = p2)
		if (p2->c_time > 0)
			t -= p2->c_time;
	p1->c_next = pnew;
	pnew->c_next = p2;
	pnew->c_time = t;
	if (p2)
		p2->c_time -= t;
	splx(s);
}

/*
 * untimeout is called to remove a function timeout call
 * from the callout structure.
 */
untimeout(func, arg)
	int (*func)();
	caddr_t arg;
{
	register struct callout *p1, *p2;
	register int s;

	s = splhigh();
	for (p1 = &calltodo; (p2 = p1->c_next) != 0; p1 = p2) {
		if (p2->c_func == func && p2->c_arg == arg) {
			if (p2->c_next && p2->c_time > 0)
				p2->c_next->c_time += p2->c_time;
			p1->c_next = p2->c_next;
			p2->c_next = callfree;
			callfree = p2;
			break;
		}
	}
	splx(s);
}

/*
 * Compute number of hz until specified time.
 * Used to compute third argument to timeout() from an
 * absolute time.
 */
hzto(tv)
	struct timeval *tv;
{
	register long ticks;
	register long sec;
	int s = splhigh();

	/*
	 * If number of milliseconds will fit in 32 bit arithmetic,
	 * then compute number of milliseconds to time and scale to
	 * ticks.  Otherwise just compute number of hz in time, rounding
	 * times greater than representible to maximum value.
	 *
	 * Delta times less than 25 days can be computed ``exactly''.
	 * Maximum value for any timeout in 10ms ticks is 250 days.
	 */
	sec = tv->tv_sec - time.tv_sec;
	if (sec <= 0x7fffffff / 1000 - 1000)
		ticks = ((tv->tv_sec - time.tv_sec) * 1000 +
			(tv->tv_usec - time.tv_usec) / 1000) / (tick / 1000);
	else if (sec <= 0x7fffffff / hz)
		ticks = sec * hz;
	else
		ticks = 0x7fffffff;
	splx(s);
	return (ticks);
}