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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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/** @addtogroup time
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 * @{
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 */
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/**
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 * @file
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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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#include <time/clock.h>
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#include <time/timeout.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>
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#include <sysinfo/sysinfo.h>
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#include <arch/barrier.h>
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#include <mm/frame.h>
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#include <ddi/ddi.h>
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/* Pointer to variable with uptime */
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uptime_t *uptime;
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/** Physical memory area of the real time clock */
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static parea_t clock_parea;
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/* Variable holding fragment of second, so that we would update
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 * seconds correctly
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 */
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static unative_t secfrag = 0;
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/** Initialize realtime clock counter
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 *
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 * The applications (and sometimes kernel) need to access accurate
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 * information about realtime data. We allocate 1 page with these
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 * data and update it periodically.
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 */
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void clock_counter_init(void)
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{
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    void *faddr;
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    faddr = frame_alloc(ONE_FRAME, FRAME_ATOMIC);
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    if (!faddr)
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        panic("Cannot allocate page for clock");
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    uptime = (uptime_t *) PA2KA(faddr);
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    uptime->seconds1 = 0;
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    uptime->seconds2 = 0;
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    uptime->useconds = 0;
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    clock_parea.pbase = (uintptr_t) faddr;
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    clock_parea.vbase = (uintptr_t) uptime;
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    clock_parea.frames = 1;
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    clock_parea.cacheable = true;
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    ddi_parea_register(&clock_parea);
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    /*
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     * Prepare information for the userspace so that it can successfully
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     * physmem_map() the clock_parea.
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     */
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    sysinfo_set_item_val("clock.cacheable", NULL, (unative_t) true);
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    sysinfo_set_item_val("clock.faddr", NULL, (unative_t) faddr);
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}
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/** Update public counters
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 *
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 * Update it only on first processor
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 * TODO: Do we really need so many write barriers?
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 */
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static void clock_update_counters(void)
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{
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    if (CPU->id == 0) {
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        secfrag += 1000000 / HZ;
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        if (secfrag >= 1000000) {
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            secfrag -= 1000000;
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            uptime->seconds1++;
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            write_barrier();
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            uptime->useconds = secfrag;
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            write_barrier();
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            uptime->seconds2 = uptime->seconds1;
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        } else
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            uptime->useconds += 1000000 / HZ;
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    }
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}
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/** 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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    count_t missed_clock_ticks = CPU->missed_clock_ticks;
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    int i;
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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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    for (i = 0; i <= missed_clock_ticks; i++) {
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        clock_update_counters();
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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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    CPU->missed_clock_ticks = 0;
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    /*
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     * Do CPU usage accounting and find out whether to preempt THREAD.
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     */
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    if (THREAD) {
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        uint64_t ticks;
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        spinlock_lock(&CPU->lock);
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        CPU->needs_relink += 1 + missed_clock_ticks;
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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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            if (ticks >= 1 + missed_clock_ticks)
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                THREAD->ticks -= 1 + missed_clock_ticks;
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            else
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                THREAD->ticks = 0;
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        }
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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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}
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/** @}
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 */