122 lines
3.4 KiB
C
122 lines
3.4 KiB
C
/*
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* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
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* The President and Fellows of Harvard College.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <types.h>
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#include <lib.h>
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#include <cpu.h>
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#include <wchan.h>
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#include <clock.h>
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#include <thread.h>
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#include <current.h>
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/*
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* Time handling.
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*
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* This is pretty primitive. A real kernel will typically have some
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* kind of support for scheduling callbacks to happen at specific
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* points in the future, usually with more resolution than one second.
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*
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* A real kernel also has to maintain the time of day; in OS/161 we
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* skimp on that because we have a known-good hardware clock.
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*/
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/*
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* Timing constants. These should be tuned along with any work done on
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* the scheduler.
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*/
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#define SCHEDULE_HARDCLOCKS 4 /* Reschedule every 4 hardclocks. */
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#define MIGRATE_HARDCLOCKS 16 /* Migrate every 16 hardclocks. */
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/*
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* Once a second, everything waiting on lbolt is awakened by CPU 0.
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*/
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static struct wchan *lbolt;
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static struct spinlock lbolt_lock;
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/*
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* Setup.
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*/
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void
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hardclock_bootstrap(void)
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{
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spinlock_init(&lbolt_lock);
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lbolt = wchan_create("lbolt");
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if (lbolt == NULL) {
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panic("Couldn't create lbolt\n");
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}
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}
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/*
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* This is called once per second, on one processor, by the timer
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* code.
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*/
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void
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timerclock(void)
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{
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/* Just broadcast on lbolt */
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spinlock_acquire(&lbolt_lock);
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wchan_wakeall(lbolt, &lbolt_lock);
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spinlock_release(&lbolt_lock);
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}
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/*
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* This is called HZ times a second (on each processor) by the timer
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* code.
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*/
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void
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hardclock(void)
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{
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/*
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* Collect statistics here as desired.
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*/
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curcpu->c_hardclocks++;
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if ((curcpu->c_hardclocks % MIGRATE_HARDCLOCKS) == 0) {
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thread_consider_migration();
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}
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if ((curcpu->c_hardclocks % SCHEDULE_HARDCLOCKS) == 0) {
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schedule();
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}
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thread_yield();
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}
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/*
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* Suspend execution for n seconds.
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*/
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void
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clocksleep(int num_secs)
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{
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spinlock_acquire(&lbolt_lock);
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while (num_secs > 0) {
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wchan_sleep(lbolt, &lbolt_lock);
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num_secs--;
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}
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spinlock_release(&lbolt_lock);
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}
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