timeout.c

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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.
 */

#include <time/timeout.h>
#include <typedefs.h>
#include <arch/types.h>
#include <config.h>
#include <panic.h>
#include <synch/spinlock.h>
#include <func.h>
#include <cpu.h>
#include <arch/asm.h>
#include <arch.h>


void timeout_init(void)
{
        spinlock_initialize(&CPU->timeoutlock, "timeout_lock");
        list_initialize(&CPU->timeout_active_head);
}


void timeout_reinitialize(timeout_t *t)
{
        t->cpu = NULL;
        t->ticks = 0;
        t->handler = NULL;
        t->arg = NULL;
        link_initialize(&t->link);
}


void timeout_initialize(timeout_t *t)
{
        spinlock_initialize(&t->lock, "timeout_t_lock");
        timeout_reinitialize(t);
}


void timeout_register(timeout_t *t, __u64 time, timeout_handler_t f, void *arg)
{
        timeout_t *hlp = NULL;
        link_t *l, *m;
        ipl_t ipl;
        __u64 sum;

        ipl = interrupts_disable();
        spinlock_lock(&CPU->timeoutlock);
        spinlock_lock(&t->lock);

        if (t->cpu)
                panic("t->cpu != 0");

        t->cpu = CPU;
        t->ticks = us2ticks(time);
        
        t->handler = f;
        t->arg = arg;

        /*
         * Insert t into the active timeouts list according to t->ticks.
         */
        sum = 0;
        l = CPU->timeout_active_head.next;
        while (l != &CPU->timeout_active_head) {
                hlp = list_get_instance(l, timeout_t, link);
                spinlock_lock(&hlp->lock);
                if (t->ticks < sum + hlp->ticks) {
                        spinlock_unlock(&hlp->lock);
                        break;
                }
                sum += hlp->ticks;
                spinlock_unlock(&hlp->lock);
                l = l->next;
        }

        m = l->prev;
        list_prepend(&t->link, m); /* avoid using l->prev */

        /*
         * Adjust t->ticks according to ticks accumulated in h's predecessors.
         */
        t->ticks -= sum;

        /*
         * Decrease ticks of t's immediate succesor by t->ticks.
         */
        if (l != &CPU->timeout_active_head) {
                spinlock_lock(&hlp->lock);
                hlp->ticks -= t->ticks;
                spinlock_unlock(&hlp->lock);
        }

        spinlock_unlock(&t->lock);
        spinlock_unlock(&CPU->timeoutlock);
        interrupts_restore(ipl);
}


bool timeout_unregister(timeout_t *t)
{
        timeout_t *hlp;
        link_t *l;
        ipl_t ipl;

grab_locks:
        ipl = interrupts_disable();
        spinlock_lock(&t->lock);
        if (!t->cpu) {
                spinlock_unlock(&t->lock);
                interrupts_restore(ipl);
                return false;
        }
        if (!spinlock_trylock(&t->cpu->timeoutlock)) {
                spinlock_unlock(&t->lock);
                interrupts_restore(ipl);                
                goto grab_locks;
        }
        
        /*
         * Now we know for sure that t hasn't been activated yet
         * and is lurking in t->cpu->timeout_active_head queue.
         */

        l = t->link.next;
        if (l != &t->cpu->timeout_active_head) {
                hlp = list_get_instance(l, timeout_t, link);
                spinlock_lock(&hlp->lock);
                hlp->ticks += t->ticks;
                spinlock_unlock(&hlp->lock);
        }
        
        list_remove(&t->link);
        spinlock_unlock(&t->cpu->timeoutlock);

        timeout_reinitialize(t);
        spinlock_unlock(&t->lock);

        interrupts_restore(ipl);
        return true;
}

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