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/*
 * Copyright (C) 2001-2004 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

/**
 * @file    clock.c
 * @brief   High-level clock interrupt handler.
 *
 * This file contains the clock() function which is the source
 * of preemption. It is also responsible for executing expired
 * timeouts.
 */
 
#include <time/clock.h>
#include <time/timeout.h>
#include <arch/types.h>
#include <config.h>
#include <synch/spinlock.h>
#include <synch/waitq.h>
#include <func.h>
#include <proc/scheduler.h>
#include <cpu.h>
#include <arch.h>
#include <adt/list.h>
#include <atomic.h>
#include <proc/thread.h>

/** Clock routine
 *
 * Clock routine executed from clock interrupt handler
 * (assuming interrupts_disable()'d). Runs expired timeouts
 * and preemptive scheduling.
 *
 */
void clock(void)
{
    link_t *l;
    timeout_t *h;
    timeout_handler_t f;
    void *arg;

    /*
     * To avoid lock ordering problems,
     * run all expired timeouts as you visit them.
     */
    spinlock_lock(&CPU->timeoutlock);
    while ((l = CPU->timeout_active_head.next) != &CPU->timeout_active_head) {
        h = list_get_instance(l, timeout_t, link);
        spinlock_lock(&h->lock);
        if (h->ticks-- != 0) {
            spinlock_unlock(&h->lock);
            break;
        }
        list_remove(l);
        f = h->handler;
        arg = h->arg;
        timeout_reinitialize(h);
        spinlock_unlock(&h->lock);  
        spinlock_unlock(&CPU->timeoutlock);

        f(arg);

        spinlock_lock(&CPU->timeoutlock);
    }
    spinlock_unlock(&CPU->timeoutlock);

    /*
     * Do CPU usage accounting and find out whether to preempt THREAD.
     */

    if (THREAD) {
        __u64 ticks;
        
        spinlock_lock(&CPU->lock);
        CPU->needs_relink++;
        spinlock_unlock(&CPU->lock);    
    
        spinlock_lock(&THREAD->lock);
        if ((ticks = THREAD->ticks))
            THREAD->ticks--;
        spinlock_unlock(&THREAD->lock);
        
        if (!ticks && !PREEMPTION_DISABLED) {
            scheduler();
        }
    }

}