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1 jermar 1
/*
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 * Copyright (C) 2001-2004 Jakub Jermar
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 * All rights reserved.
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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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 *
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 * - 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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 * - 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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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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1264 jermar 29
/**
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 * @file    clock.c
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 * @brief   High-level clock interrupt handler.
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 *
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 * This file contains the clock() function which is the source
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 * of preemption. It is also responsible for executing expired
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 * timeouts.
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 */
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1 jermar 38
#include <time/clock.h>
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#include <time/timeout.h>
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#include <arch/types.h>
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#include <config.h>
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#include <synch/spinlock.h>
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#include <synch/waitq.h>
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#include <func.h>
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#include <proc/scheduler.h>
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#include <cpu.h>
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#include <arch.h>
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#include <adt/list.h>
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#include <atomic.h>
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#include <proc/thread.h>
1 jermar 51
 
107 decky 52
/** Clock routine
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 *
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 * Clock routine executed from clock interrupt handler
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 * (assuming interrupts_disable()'d). Runs expired timeouts
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 * and preemptive scheduling.
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 *
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 */
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void clock(void)
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{
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    link_t *l;
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    timeout_t *h;
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    timeout_handler_t f;
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    void *arg;
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    /*
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     * To avoid lock ordering problems,
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     * run all expired timeouts as you visit them.
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     */
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    spinlock_lock(&CPU->timeoutlock);
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    while ((l = CPU->timeout_active_head.next) != &CPU->timeout_active_head) {
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        h = list_get_instance(l, timeout_t, link);
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        spinlock_lock(&h->lock);
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        if (h->ticks-- != 0) {
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            spinlock_unlock(&h->lock);
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            break;
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        }
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        list_remove(l);
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        f = h->handler;
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        arg = h->arg;
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        timeout_reinitialize(h);
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        spinlock_unlock(&h->lock); 
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        spinlock_unlock(&CPU->timeoutlock);
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        f(arg);
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        spinlock_lock(&CPU->timeoutlock);
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    }
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    spinlock_unlock(&CPU->timeoutlock);
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    /*
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     * Do CPU usage accounting and find out whether to preempt THREAD.
1 jermar 93
     */
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15 jermar 95
    if (THREAD) {
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        __u64 ticks;
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        spinlock_lock(&CPU->lock);
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        CPU->needs_relink++;
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        spinlock_unlock(&CPU->lock);   
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        spinlock_lock(&THREAD->lock);
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        if ((ticks = THREAD->ticks))
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            THREAD->ticks--;
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        spinlock_unlock(&THREAD->lock);
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        if (!ticks && !PREEMPTION_DISABLED) {
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            scheduler();
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        }
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    }
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}