kernel/time/tick-common.c - maze/linux - Git at Google

 /*
  * linux/kernel/time/tick-common.c
  *
  * This file contains the base functions to manage periodic tick
  * related events.
  *
  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
  *
  * This code is licenced under the GPL version 2. For details see
  * kernel-base/COPYING.
  */
 #include <linux/cpu.h>
 #include <linux/err.h>
 #include <linux/hrtimer.h>
 #include <linux/interrupt.h>
 #include <linux/percpu.h>
 #include <linux/profile.h>
 #include <linux/sched.h>
 #include <linux/tick.h>

 #include <asm/irq_regs.h>

 #include "tick-internal.h"

 /*
  * Tick devices
  */
 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
 /*
  * Tick next event: keeps track of the tick time
  */
 ktime_t tick_next_period;
 ktime_t tick_period;
 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
 DEFINE_SPINLOCK(tick_device_lock);

 /*
  * Debugging: see timer_list.c
  */
 struct tick_device *tick_get_device(int cpu)
 {
 	return &per_cpu(tick_cpu_device, cpu);
 }

 /**
  * tick_is_oneshot_available - check for a oneshot capable event device
  */
 int tick_is_oneshot_available(void)
 {
 	struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;

 	return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
 }

 /*
  * Periodic tick
  */
 static void tick_periodic(int cpu)
 {
 	if (tick_do_timer_cpu == cpu) {
 		write_seqlock(&xtime_lock);

 		/* Keep track of the next tick event */
 		tick_next_period = ktime_add(tick_next_period, tick_period);

 		do_timer(1);
 		write_sequnlock(&xtime_lock);
 	}

 	update_process_times(user_mode(get_irq_regs()));
 	profile_tick(CPU_PROFILING);
 }

 /*
  * Event handler for periodic ticks
  */
 void tick_handle_periodic(struct clock_event_device *dev)
 {
 	int cpu = smp_processor_id();
 	ktime_t next;

 	tick_periodic(cpu);

 	if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
 		return;
 	/*
 	 * Setup the next period for devices, which do not have
 	 * periodic mode:
 	 */
 	next = ktime_add(dev->next_event, tick_period);
 	for (;;) {
 		if (!clockevents_program_event(dev, next, ktime_get()))
 			return;
 		tick_periodic(cpu);
 		next = ktime_add(next, tick_period);
 	}
 }

 /*
  * Setup the device for a periodic tick
  */
 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
 {
 	tick_set_periodic_handler(dev, broadcast);

 	/* Broadcast setup ? */
 	if (!tick_device_is_functional(dev))
 		return;

 	if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
 	    !tick_broadcast_oneshot_active()) {
 		clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
 	} else {
 		unsigned long seq;
 		ktime_t next;

 		do {
 			seq = read_seqbegin(&xtime_lock);
 			next = tick_next_period;
 		} while (read_seqretry(&xtime_lock, seq));

 		clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);

 		for (;;) {
 			if (!clockevents_program_event(dev, next, ktime_get()))
 				return;
 			next = ktime_add(next, tick_period);
 		}
 	}
 }

 /*
  * Setup the tick device
  */
 static void tick_setup_device(struct tick_device *td,
 			      struct clock_event_device *newdev, int cpu,
 			      const struct cpumask *cpumask)
 {
 	ktime_t next_event;
 	void (*handler)(struct clock_event_device *) = NULL;

 	/*
 	 * First device setup ?
 	 */
 	if (!td->evtdev) {
 		/*
 		 * If no cpu took the do_timer update, assign it to
 		 * this cpu:
 		 */
 		if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
 			tick_do_timer_cpu = cpu;
 			tick_next_period = ktime_get();
 			tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
 		}

 		/*
 		 * Startup in periodic mode first.
 		 */
 		td->mode = TICKDEV_MODE_PERIODIC;
 	} else {
 		handler = td->evtdev->event_handler;
 		next_event = td->evtdev->next_event;
 		td->evtdev->event_handler = clockevents_handle_noop;
 	}

 	td->evtdev = newdev;

 	/*
 	 * When the device is not per cpu, pin the interrupt to the
 	 * current cpu:
 	 */
 	if (!cpumask_equal(newdev->cpumask, cpumask))
 		irq_set_affinity(newdev->irq, cpumask);

 	/*
 	 * When global broadcasting is active, check if the current
 	 * device is registered as a placeholder for broadcast mode.
 	 * This allows us to handle this x86 misfeature in a generic
 	 * way.
 	 */
 	if (tick_device_uses_broadcast(newdev, cpu))
 		return;

 	if (td->mode == TICKDEV_MODE_PERIODIC)
 		tick_setup_periodic(newdev, 0);
 	else
 		tick_setup_oneshot(newdev, handler, next_event);
 }

 /*
  * Check, if the new registered device should be used.
  */
 static int tick_check_new_device(struct clock_event_device *newdev)
 {
 	struct clock_event_device *curdev;
 	struct tick_device *td;
 	int cpu, ret = NOTIFY_OK;
 	unsigned long flags;

 	spin_lock_irqsave(&tick_device_lock, flags);

 	cpu = smp_processor_id();
 	if (!cpumask_test_cpu(cpu, newdev->cpumask))
 		goto out_bc;

 	td = &per_cpu(tick_cpu_device, cpu);
 	curdev = td->evtdev;

 	/* cpu local device ? */
 	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {

 		/*
 		 * If the cpu affinity of the device interrupt can not
 		 * be set, ignore it.
 		 */
 		if (!irq_can_set_affinity(newdev->irq))
 			goto out_bc;

 		/*
 		 * If we have a cpu local device already, do not replace it
 		 * by a non cpu local device
 		 */
 		if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
 			goto out_bc;
 	}

 	/*
 	 * If we have an active device, then check the rating and the oneshot
 	 * feature.
 	 */
 	if (curdev) {
 		/*
 		 * Prefer one shot capable devices !
 		 */
 		if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
 		    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
 			goto out_bc;
 		/*
 		 * Check the rating
 		 */
 		if (curdev->rating >= newdev->rating)
 			goto out_bc;
 	}

 	/*
 	 * Replace the eventually existing device by the new
 	 * device. If the current device is the broadcast device, do
 	 * not give it back to the clockevents layer !
 	 */
 	if (tick_is_broadcast_device(curdev)) {
 		clockevents_shutdown(curdev);
 		curdev = NULL;
 	}
 	clockevents_exchange_device(curdev, newdev);
 	tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
 	if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
 		tick_oneshot_notify();

 	spin_unlock_irqrestore(&tick_device_lock, flags);
 	return NOTIFY_STOP;

 out_bc:
 	/*
 	 * Can the new device be used as a broadcast device ?
 	 */
 	if (tick_check_broadcast_device(newdev))
 		ret = NOTIFY_STOP;

 	spin_unlock_irqrestore(&tick_device_lock, flags);

 	return ret;
 }

 /*
  * Transfer the do_timer job away from a dying cpu.
  *
  * Called with interrupts disabled.
  */
 static void tick_handover_do_timer(int *cpup)
 {
 	if (*cpup == tick_do_timer_cpu) {
 		int cpu = cpumask_first(cpu_online_mask);

 		tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
 			TICK_DO_TIMER_NONE;
 	}
 }

 /*
  * Shutdown an event device on a given cpu:
  *
  * This is called on a life CPU, when a CPU is dead. So we cannot
  * access the hardware device itself.
  * We just set the mode and remove it from the lists.
  */
 static void tick_shutdown(unsigned int *cpup)
 {
 	struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
 	struct clock_event_device *dev = td->evtdev;
 	unsigned long flags;

 	spin_lock_irqsave(&tick_device_lock, flags);
 	td->mode = TICKDEV_MODE_PERIODIC;
 	if (dev) {
 		/*
 		 * Prevent that the clock events layer tries to call
 		 * the set mode function!
 		 */
 		dev->mode = CLOCK_EVT_MODE_UNUSED;
 		clockevents_exchange_device(dev, NULL);
 		td->evtdev = NULL;
 	}
 	spin_unlock_irqrestore(&tick_device_lock, flags);
 }

 static void tick_suspend(void)
 {
 	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 	unsigned long flags;

 	spin_lock_irqsave(&tick_device_lock, flags);
 	clockevents_shutdown(td->evtdev);
 	spin_unlock_irqrestore(&tick_device_lock, flags);
 }

 static void tick_resume(void)
 {
 	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 	unsigned long flags;
 	int broadcast = tick_resume_broadcast();

 	spin_lock_irqsave(&tick_device_lock, flags);
 	clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);

 	if (!broadcast) {
 		if (td->mode == TICKDEV_MODE_PERIODIC)
 			tick_setup_periodic(td->evtdev, 0);
 		else
 			tick_resume_oneshot();
 	}
 	spin_unlock_irqrestore(&tick_device_lock, flags);
 }

 /*
  * Notification about clock event devices
  */
 static int tick_notify(struct notifier_block *nb, unsigned long reason,
 			       void *dev)
 {
 	switch (reason) {

 	case CLOCK_EVT_NOTIFY_ADD:
 		return tick_check_new_device(dev);

 	case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 	case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 	case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 		tick_broadcast_on_off(reason, dev);
 		break;

 	case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
 	case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
 		tick_broadcast_oneshot_control(reason);
 		break;

 	case CLOCK_EVT_NOTIFY_CPU_DYING:
 		tick_handover_do_timer(dev);
 		break;

 	case CLOCK_EVT_NOTIFY_CPU_DEAD:
 		tick_shutdown_broadcast_oneshot(dev);
 		tick_shutdown_broadcast(dev);
 		tick_shutdown(dev);
 		break;

 	case CLOCK_EVT_NOTIFY_SUSPEND:
 		tick_suspend();
 		tick_suspend_broadcast();
 		break;

 	case CLOCK_EVT_NOTIFY_RESUME:
 		tick_resume();
 		break;

 	default:
 		break;
 	}

 	return NOTIFY_OK;
 }

 static struct notifier_block tick_notifier = {
 	.notifier_call = tick_notify,
 };

 /**
  * tick_init - initialize the tick control
  *
  * Register the notifier with the clockevents framework
  */
 void __init tick_init(void)
 {
 	clockevents_register_notifier(&tick_notifier);
 }
	/*
	* linux/kernel/time/tick-common.c
	*
	* This file contains the base functions to manage periodic tick
	* related events.
	*
	* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
	* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
	* Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
	*
	* This code is licenced under the GPL version 2. For details see
	* kernel-base/COPYING.
	*/
	#include <linux/cpu.h>
	#include <linux/err.h>
	#include <linux/hrtimer.h>
	#include <linux/interrupt.h>
	#include <linux/percpu.h>
	#include <linux/profile.h>
	#include <linux/sched.h>
	#include <linux/tick.h>

	#include <asm/irq_regs.h>

	#include "tick-internal.h"

	/*
	* Tick devices
	*/
	DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
	/*
	* Tick next event: keeps track of the tick time
	*/
	ktime_t tick_next_period;
	ktime_t tick_period;
	int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
	DEFINE_SPINLOCK(tick_device_lock);

	/*
	* Debugging: see timer_list.c
	*/
	struct tick_device *tick_get_device(int cpu)
	{
	return &per_cpu(tick_cpu_device, cpu);
	}

	/**
	* tick_is_oneshot_available - check for a oneshot capable event device
	*/
	int tick_is_oneshot_available(void)
	{
	struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;

	return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
	}

	/*
	* Periodic tick
	*/
	static void tick_periodic(int cpu)
	{
	if (tick_do_timer_cpu == cpu) {
	write_seqlock(&xtime_lock);

	/* Keep track of the next tick event */
	tick_next_period = ktime_add(tick_next_period, tick_period);

	do_timer(1);
	write_sequnlock(&xtime_lock);
	}

	update_process_times(user_mode(get_irq_regs()));
	profile_tick(CPU_PROFILING);
	}

	/*
	* Event handler for periodic ticks
	*/
	void tick_handle_periodic(struct clock_event_device *dev)
	{
	int cpu = smp_processor_id();
	ktime_t next;

	tick_periodic(cpu);

	if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
	return;
	/*
	* Setup the next period for devices, which do not have
	* periodic mode:
	*/
	next = ktime_add(dev->next_event, tick_period);
	for (;;) {
	if (!clockevents_program_event(dev, next, ktime_get()))
	return;
	tick_periodic(cpu);
	next = ktime_add(next, tick_period);
	}
	}

	/*
	* Setup the device for a periodic tick
	*/
	void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
	{
	tick_set_periodic_handler(dev, broadcast);

	/* Broadcast setup ? */
	if (!tick_device_is_functional(dev))
	return;

	if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
	!tick_broadcast_oneshot_active()) {
	clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
	} else {
	unsigned long seq;
	ktime_t next;

	do {
	seq = read_seqbegin(&xtime_lock);
	next = tick_next_period;
	} while (read_seqretry(&xtime_lock, seq));

	clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);

	for (;;) {
	if (!clockevents_program_event(dev, next, ktime_get()))
	return;
	next = ktime_add(next, tick_period);
	}
	}
	}

	/*
	* Setup the tick device
	*/
	static void tick_setup_device(struct tick_device *td,
	struct clock_event_device *newdev, int cpu,
	const struct cpumask *cpumask)
	{
	ktime_t next_event;
	void (handler)(struct clock_event_device ) = NULL;

	/*
	* First device setup ?
	*/
	if (!td->evtdev) {
	/*
	* If no cpu took the do_timer update, assign it to
	* this cpu:
	*/
	if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
	tick_do_timer_cpu = cpu;
	tick_next_period = ktime_get();
	tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
	}

	/*
	* Startup in periodic mode first.
	*/
	td->mode = TICKDEV_MODE_PERIODIC;
	} else {
	handler = td->evtdev->event_handler;
	next_event = td->evtdev->next_event;
	td->evtdev->event_handler = clockevents_handle_noop;
	}

	td->evtdev = newdev;

	/*
	* When the device is not per cpu, pin the interrupt to the
	* current cpu:
	*/
	if (!cpumask_equal(newdev->cpumask, cpumask))
	irq_set_affinity(newdev->irq, cpumask);

	/*
	* When global broadcasting is active, check if the current
	* device is registered as a placeholder for broadcast mode.
	* This allows us to handle this x86 misfeature in a generic
	* way.
	*/
	if (tick_device_uses_broadcast(newdev, cpu))
	return;

	if (td->mode == TICKDEV_MODE_PERIODIC)
	tick_setup_periodic(newdev, 0);
	else
	tick_setup_oneshot(newdev, handler, next_event);
	}

	/*
	* Check, if the new registered device should be used.
	*/
	static int tick_check_new_device(struct clock_event_device *newdev)
	{
	struct clock_event_device *curdev;
	struct tick_device *td;
	int cpu, ret = NOTIFY_OK;
	unsigned long flags;

	spin_lock_irqsave(&tick_device_lock, flags);

	cpu = smp_processor_id();
	if (!cpumask_test_cpu(cpu, newdev->cpumask))
	goto out_bc;

	td = &per_cpu(tick_cpu_device, cpu);
	curdev = td->evtdev;

	/* cpu local device ? */
	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {

	/*
	* If the cpu affinity of the device interrupt can not
	* be set, ignore it.
	*/
	if (!irq_can_set_affinity(newdev->irq))
	goto out_bc;

	/*
	* If we have a cpu local device already, do not replace it
	* by a non cpu local device
	*/
	if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
	goto out_bc;
	}

	/*
	* If we have an active device, then check the rating and the oneshot
	* feature.
	*/
	if (curdev) {
	/*
	* Prefer one shot capable devices !
	*/
	if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
	!(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
	goto out_bc;
	/*
	* Check the rating
	*/
	if (curdev->rating >= newdev->rating)
	goto out_bc;
	}

	/*
	* Replace the eventually existing device by the new
	* device. If the current device is the broadcast device, do
	* not give it back to the clockevents layer !
	*/
	if (tick_is_broadcast_device(curdev)) {
	clockevents_shutdown(curdev);
	curdev = NULL;
	}
	clockevents_exchange_device(curdev, newdev);
	tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
	if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
	tick_oneshot_notify();

	spin_unlock_irqrestore(&tick_device_lock, flags);
	return NOTIFY_STOP;

	out_bc:
	/*
	* Can the new device be used as a broadcast device ?
	*/
	if (tick_check_broadcast_device(newdev))
	ret = NOTIFY_STOP;

	spin_unlock_irqrestore(&tick_device_lock, flags);

	return ret;
	}

	/*
	* Transfer the do_timer job away from a dying cpu.
	*
	* Called with interrupts disabled.
	*/
	static void tick_handover_do_timer(int *cpup)
	{
	if (*cpup == tick_do_timer_cpu) {
	int cpu = cpumask_first(cpu_online_mask);

	tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
	TICK_DO_TIMER_NONE;
	}
	}

	/*
	* Shutdown an event device on a given cpu:
	*
	* This is called on a life CPU, when a CPU is dead. So we cannot
	* access the hardware device itself.
	* We just set the mode and remove it from the lists.
	*/
	static void tick_shutdown(unsigned int *cpup)
	{
	struct tick_device td = &per_cpu(tick_cpu_device, cpup);
	struct clock_event_device *dev = td->evtdev;
	unsigned long flags;

	spin_lock_irqsave(&tick_device_lock, flags);
	td->mode = TICKDEV_MODE_PERIODIC;
	if (dev) {
	/*
	* Prevent that the clock events layer tries to call
	* the set mode function!
	*/
	dev->mode = CLOCK_EVT_MODE_UNUSED;
	clockevents_exchange_device(dev, NULL);
	td->evtdev = NULL;
	}
	spin_unlock_irqrestore(&tick_device_lock, flags);
	}

	static void tick_suspend(void)
	{
	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
	unsigned long flags;

	spin_lock_irqsave(&tick_device_lock, flags);
	clockevents_shutdown(td->evtdev);
	spin_unlock_irqrestore(&tick_device_lock, flags);
	}

	static void tick_resume(void)
	{
	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
	unsigned long flags;
	int broadcast = tick_resume_broadcast();

	spin_lock_irqsave(&tick_device_lock, flags);
	clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);

	if (!broadcast) {
	if (td->mode == TICKDEV_MODE_PERIODIC)
	tick_setup_periodic(td->evtdev, 0);
	else
	tick_resume_oneshot();
	}
	spin_unlock_irqrestore(&tick_device_lock, flags);
	}

	/*
	* Notification about clock event devices
	*/
	static int tick_notify(struct notifier_block *nb, unsigned long reason,
	void *dev)
	{
	switch (reason) {

	case CLOCK_EVT_NOTIFY_ADD:
	return tick_check_new_device(dev);

	case CLOCK_EVT_NOTIFY_BROADCAST_ON:
	case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
	case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
	tick_broadcast_on_off(reason, dev);
	break;

	case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
	case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
	tick_broadcast_oneshot_control(reason);
	break;

	case CLOCK_EVT_NOTIFY_CPU_DYING:
	tick_handover_do_timer(dev);
	break;

	case CLOCK_EVT_NOTIFY_CPU_DEAD:
	tick_shutdown_broadcast_oneshot(dev);
	tick_shutdown_broadcast(dev);
	tick_shutdown(dev);
	break;

	case CLOCK_EVT_NOTIFY_SUSPEND:
	tick_suspend();
	tick_suspend_broadcast();
	break;

	case CLOCK_EVT_NOTIFY_RESUME:
	tick_resume();
	break;

	default:
	break;
	}

	return NOTIFY_OK;
	}

	static struct notifier_block tick_notifier = {
	.notifier_call = tick_notify,
	};

	/**
	* tick_init - initialize the tick control
	*
	* Register the notifier with the clockevents framework
	*/
	void __init tick_init(void)
	{
	clockevents_register_notifier(&tick_notifier);
	}