kern_clock.c

ReactOS是一些高手根据Windows XP的内核编写出的类XP。内核实现机理和API函数调用几乎相同。甚至可以兼容XP的程序。喜欢研究系统内核的人可以看一看。

/*
 * Copyright (c) 1997-1998 University of Utah and the Flux Group.
 * All rights reserved.
 *
 * This file is part of the Flux OSKit.  The OSKit is free software, also known
 * as "open source;" you can redistribute it and/or modify it under the terms
 * of the GNU General Public License (GPL), version 2, as published by the Free
 * Software Foundation (FSF).  To explore alternate licensing terms, contact
 * the University of Utah at [e-mail] or [phone].
 *
 * The OSKit is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GPL for more details.  You should have
 * received a copy of the GPL along with the OSKit; see the file COPYING.  If
 * not, write to the FSF, 59 Temple Place #330, Boston, MA 02111-1307, USA.
 */
/*
 * I am having no mercy with this file.
 * I ripped out everything I didn't need
 */
/*-
 * Copyright (c) 1982, 1986, 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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	8.5 (Berkeley) 1/21/94
 * $\Id: kern_clock.c,v 1.26 1996/07/30 16:59:22 bde Exp $
 */

/* Portions of this software are covered by the following: */
/******************************************************************************
 *                                                                            *
 * Copyright (c) David L. Mills 1993, 1994                                    *
 *                                                                            *
 * Permission to use, copy, modify, and distribute this software and its      *
 * documentation for any purpose and without fee is hereby granted, provided  *
 * that the above copyright notice appears in all copies and that both the    *
 * copyright notice and this permission notice appear in supporting           *
 * documentation, and that the name University of Delaware not be used in     *
 * advertising or publicity pertaining to distribution of the software        *
 * without specific, written prior permission.  The University of Delaware    *
 * makes no representations about the suitability this software for any       *
 * purpose.  It is provided "as is" without express or implied warranty.      *
 *                                                                            *
 *****************************************************************************/

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/kernel.h>
#include <sys/proc.h>

/* Exported to machdep.c. */
struct callout *callfree, *callout;

struct callout calltodo;

long tk_cancc;
long tk_nin;
long tk_nout;
long tk_rawcc;

/*
 * Clock handling routines.
 *
 * This code is written to operate with two timers that run independently of
 * each other.  The main clock, running hz times per second, is used to keep
 * track of real time.  The second timer handles kernel and user profiling,
 * and does resource use estimation.  If the second timer is programmable,
 * it is randomized to avoid aliasing between the two clocks.  For example,
 * the randomization prevents an adversary from always giving up the cpu
 * just before its quantum expires.  Otherwise, it would never accumulate
 * cpu ticks.  The mean frequency of the second timer is stathz.
 *
 * If no second timer exists, stathz will be zero; in this case we drive
 * profiling and statistics off the main clock.  This WILL NOT be accurate;
 * do not do it unless absolutely necessary.
 *
 * The statistics clock may (or may not) be run at a higher rate while
 * profiling.  This profile clock runs at profhz.  We require that profhz
 * be an integral multiple of stathz.
 *
 * If the statistics clock is running fast, it must be divided by the ratio
 * profhz/stathz for statistics.  (For profiling, every tick counts.)
 */

/*
 * TODO:
 *	allocate more timeout table slots when table overflows.
 */

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

int	ticks;
volatile struct	timeval kern_time;
volatile struct	timeval mono_time;

/*
 * Software (low priority) clock interrupt.
 * Run periodic events from timeout queue.
 */
/*ARGSUSED*/
void
softclock()
{
	register struct callout *c;
	register void *arg;
	register void (*func) __P((void *));
	register int s;

	s = splhigh();
	while ((c = calltodo.c_next) != NULL && c->c_time <= 0) {
		func = c->c_func;
		arg = c->c_arg;
		calltodo.c_next = c->c_next;
		c->c_next = callfree;
		callfree = c;
		splx(s);
		(*func)(arg);
		(void) splhigh();
	}
	splx(s);
}

/*
 * timeout --
 *	Execute a function after a specified length of time.
 *
 * untimeout --
 *	Cancel previous timeout function call.
 *
 *	See AT&T BCI Driver Reference Manual for specification.  This
 *	implementation differs from that one in that no identification
 *	value is returned from timeout, rather, the original arguments
 *	to timeout are used to identify entries for untimeout.
 */
void
timeout(ftn, arg, ticks)
	timeout_t ftn;
	void *arg;
	register int ticks;
{
	register struct callout *new, *p, *t;
	register int s;

	if (ticks <= 0)
		ticks = 1;

	/* Lock out the clock. */
	s = splhigh();

	/* Fill in the next free callout structure. */
	if (callfree == NULL)
		panic("timeout table full");
	new = callfree;
	callfree = new->c_next;
	new->c_arg = arg;
	new->c_func = ftn;

	/*
	 * The time for each event is stored as a difference from the time
	 * of the previous event on the queue.  Walk the queue, correcting
	 * the ticks argument for queue entries passed.  Correct the ticks
	 * value for the queue entry immediately after the insertion point
	 * as well.  Watch out for negative c_time values; these represent
	 * overdue events.
	 */
	for (p = &calltodo;
	    (t = p->c_next) != NULL && ticks > t->c_time; p = t)
		if (t->c_time > 0)
			ticks -= t->c_time;
	new->c_time = ticks;
	if (t != NULL)
		t->c_time -= ticks;

	/* Insert the new entry into the queue. */
	p->c_next = new;
	new->c_next = t;
	splx(s);
}

void
untimeout(ftn, arg)
	timeout_t ftn;
	void *arg;
{
	register struct callout *p, *t;
	register int s;

	s = splhigh();
	for (p = &calltodo; (t = p->c_next) != NULL; p = t)
		if (t->c_func == ftn && t->c_arg == arg) {
			/* Increment next entry's tick count. */
			if (t->c_next && t->c_time > 0)
				t->c_next->c_time += t->c_time;

			/* Move entry from callout queue to callfree queue. */
			p->c_next = t->c_next;
			t->c_next = callfree;
			callfree = t;
			break;
		}
	splx(s);
}

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

	/*
	 * 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 have 32 bits, then the maximum value for any timeout in
	 * 10ms ticks is 248 days.
	 */
	s = splclock();
	sec = tv->tv_sec - kern_time.tv_sec;
	usec = tv->tv_usec - kern_time.tv_usec;
	splx(s);
	if (usec < 0) {
		sec--;
		usec += 1000000;
	}
	if (sec < 0) {
#ifdef DIAGNOSTIC
		printf("hzto: negative time difference %ld sec %ld usec\n",
		       sec, usec);
#endif
		ticks = 1;
	} 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 (ticks);
}