source: mainline/generic/src/time/clock.c@ d6e5cbc

/*
 * 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>
#include <sysinfo/sysinfo.h>
#include <arch/barrier.h>

/* Pointers to public variables with time */
struct ptime {
        __native seconds;
        __native useconds;
        __native useconds2;
};
struct ptime *public_time;
/* Variable holding fragment of second, so that we would update
 * seconds correctly
 */
static __native secfrag = 0;

/** Initialize realtime clock counter
 *
 * The applications (and sometimes kernel) need to access accurate
 * information about realtime data. We allocate 1 page with these 
 * data and update it periodically.
 *
 * 
 */
void clock_counter_init(void)
{
        void *faddr;

        faddr = (void *)PFN2ADDR(frame_alloc(0, FRAME_ATOMIC));
        if (!faddr)
                panic("Cannot allocate page for clock");
        
        public_time = (struct ptime *)PA2KA(faddr);

        /* TODO: We would need some arch dependent settings here */
        public_time->seconds = 0;
        public_time->useconds = 0; 

        sysinfo_set_item_val("clock.faddr", NULL, (__native)faddr);
}


/** Update public counters
 *
 * Update it only on first processor
 * TODO: Do we really need so many write barriers? 
 */
static void clock_update_counters(void)
{
        if (CPU->id == 0) {
                secfrag += 1000000/HZ;
                if (secfrag >= 1000000) {
                        public_time->useconds = 0;
                        write_barrier();
                        public_time->seconds++;
                        secfrag = 0;
                } else
                        public_time->useconds += 1000000/HZ;
                write_barrier();
                public_time->useconds2 = public_time->useconds;
                write_barrier();
        }
}

/** 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;
        int i;

        /*
         * To avoid lock ordering problems,
         * run all expired timeouts as you visit them.
         */
        for (i = 0; i <= CPU->missed_clock_ticks; i++) {
                clock_update_counters();
                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);
        }
        CPU->missed_clock_ticks = 0;

        /*
         * 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();
                }
        }

}