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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.

 */

/** @addtogroup time

 * @{

 */

/**

 * @file

 * @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 <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>

#include <mm/frame.h>

#include <ddi/ddi.h>

/* Pointer to variable with uptime */

uptime_t *uptime;

/** Physical memory area of the real time clock */

static parea_t clock_parea;

/* Variable holding fragment of second, so that we would update

 * seconds correctly

 */

static unative_t 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 = frame_alloc(ONE_FRAME, FRAME_ATOMIC);

	if (!faddr)

		panic("Cannot allocate page for clock");

	uptime = (uptime_t *) PA2KA(faddr);

	uptime->seconds1 = 0;

	uptime->seconds2 = 0;

	uptime->useconds = 0; 

	clock_parea.pbase = (uintptr_t) faddr;

	clock_parea.vbase = (uintptr_t) uptime;

	clock_parea.frames = 1;

	clock_parea.cacheable = true;

	ddi_parea_register(&clock_parea);

	/*

	 * Prepare information for the userspace so that it can successfully

	 * physmem_map() the clock_parea.

	 */

	sysinfo_set_item_val("clock.cacheable", NULL, (unative_t) true);

	sysinfo_set_item_val("clock.faddr", NULL, (unative_t) 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) {

			secfrag -= 1000000;

			uptime->seconds1++;

			write_barrier();

			uptime->useconds = secfrag;

			write_barrier();

			uptime->seconds2 = uptime->seconds1;

		} else

			uptime->useconds += 1000000 / HZ;

	}

}

/** 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;

	count_t missed_clock_ticks = CPU->missed_clock_ticks;

	unsigned int i;

	/*

	 * To avoid lock ordering problems,

	 * run all expired timeouts as you visit them.

	 */

	for (i = 0; i <= 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) {

		uint64_t ticks;

		spinlock_lock(&CPU->lock);

		CPU->needs_relink += 1 + missed_clock_ticks;

		spinlock_unlock(&CPU->lock);	

		spinlock_lock(&THREAD->lock);

		if ((ticks = THREAD->ticks)) {

			if (ticks >= 1 + missed_clock_ticks)

				THREAD->ticks -= 1 + missed_clock_ticks;

			else

				THREAD->ticks = 0;

		}

		spinlock_unlock(&THREAD->lock);

		if (!ticks && !PREEMPTION_DISABLED) {

#ifdef CONFIG_UDEBUG

			istate_t *istate;

#endif

			scheduler();

#ifdef CONFIG_UDEBUG

			/*

			 * Give udebug chance to stop the thread

			 * before it begins executing userspace code.

			 */

			istate = THREAD->udebug.uspace_state;

			if (istate && istate_from_uspace(istate))

				udebug_before_thread_runs();

#endif

		}

	}

}

/** @}

 */