// SPDX-License-Identifier: GPL-2.0

  /*

   * This file contains functions which emulate a local clock-event
   * device via a broadcast event source.
   *
   * 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

   */
  #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/smp.h>

  #include <linux/module.h>

  
  #include "tick-internal.h"
  
  /*
   * Broadcast support for broken x86 hardware, where the local apic
   * timer stops in C3 state.
   */

  static struct tick_device tick_broadcast_device;

  static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;
  static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
  static cpumask_var_t tmpmask __cpumask_var_read_mostly;

  static int tick_broadcast_forced;

  static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);

  #ifdef CONFIG_TICK_ONESHOT

  static void tick_broadcast_setup_oneshot(struct clock_event_device *bc);

  static void tick_broadcast_clear_oneshot(int cpu);

  static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);

  # ifdef CONFIG_HOTPLUG_CPU

  static void tick_broadcast_oneshot_offline(unsigned int cpu);

  # endif

  #else

  static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { BUG(); }

  static inline void tick_broadcast_clear_oneshot(int cpu) { }

  static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }

  # ifdef CONFIG_HOTPLUG_CPU

  static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }

  # endif

  #endif

  /*

   * Debugging: see timer_list.c
   */
  struct tick_device *tick_get_broadcast_device(void)
  {
  	return &tick_broadcast_device;
  }

  struct cpumask *tick_get_broadcast_mask(void)

  {

  	return tick_broadcast_mask;

  }
  
  /*

   * Start the device in periodic mode
   */
  static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  {

  	if (bc)

  		tick_setup_periodic(bc, 1);
  }
  
  /*
   * Check, if the device can be utilized as broadcast device:
   */

  static bool tick_check_broadcast_device(struct clock_event_device *curdev,
  					struct clock_event_device *newdev)
  {
  	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||

  	    (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||

  	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
  		return false;
  
  	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
  	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
  		return false;
  
  	return !curdev || newdev->rating > curdev->rating;
  }
  
  /*
   * Conditionally install/replace broadcast device
   */

  void tick_install_broadcast_device(struct clock_event_device *dev)

  {

  	struct clock_event_device *cur = tick_broadcast_device.evtdev;

  	if (!tick_check_broadcast_device(cur, dev))

  		return;

  	if (!try_module_get(dev->owner))
  		return;

  	clockevents_exchange_device(cur, dev);

  	if (cur)
  		cur->event_handler = clockevents_handle_noop;

  	tick_broadcast_device.evtdev = dev;

  	if (!cpumask_empty(tick_broadcast_mask))

  		tick_broadcast_start_periodic(dev);

  	/*
  	 * Inform all cpus about this. We might be in a situation
  	 * where we did not switch to oneshot mode because the per cpu
  	 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
  	 * of a oneshot capable broadcast device. Without that
  	 * notification the systems stays stuck in periodic mode
  	 * forever.
  	 */
  	if (dev->features & CLOCK_EVT_FEAT_ONESHOT)
  		tick_clock_notify();

  }
  
  /*
   * Check, if the device is the broadcast device
   */
  int tick_is_broadcast_device(struct clock_event_device *dev)
  {
  	return (dev && tick_broadcast_device.evtdev == dev);
  }

  int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
  {
  	int ret = -ENODEV;
  
  	if (tick_is_broadcast_device(dev)) {
  		raw_spin_lock(&tick_broadcast_lock);
  		ret = __clockevents_update_freq(dev, freq);
  		raw_spin_unlock(&tick_broadcast_lock);
  	}
  	return ret;
  }

  static void err_broadcast(const struct cpumask *mask)
  {
  	pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.
  ");
  }

  static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
  {
  	if (!dev->broadcast)
  		dev->broadcast = tick_broadcast;
  	if (!dev->broadcast) {
  		pr_warn_once("%s depends on broadcast, but no broadcast function available
  ",
  			     dev->name);
  		dev->broadcast = err_broadcast;
  	}
  }

  /*
   * Check, if the device is disfunctional and a place holder, which
   * needs to be handled by the broadcast device.
   */
  int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
  {

  	struct clock_event_device *bc = tick_broadcast_device.evtdev;

  	unsigned long flags;

  	int ret = 0;

  	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

  
  	/*
  	 * Devices might be registered with both periodic and oneshot
  	 * mode disabled. This signals, that the device needs to be
  	 * operated from the broadcast device and is a placeholder for
  	 * the cpu local device.
  	 */
  	if (!tick_device_is_functional(dev)) {
  		dev->event_handler = tick_handle_periodic;

  		tick_device_setup_broadcast_func(dev);

  		cpumask_set_cpu(cpu, tick_broadcast_mask);

  		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
  			tick_broadcast_start_periodic(bc);
  		else
  			tick_broadcast_setup_oneshot(bc);

  		ret = 1;

  	} else {
  		/*

  		 * Clear the broadcast bit for this cpu if the
  		 * device is not power state affected.

  		 */

  		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))

  			cpumask_clear_cpu(cpu, tick_broadcast_mask);

  		else

  			tick_device_setup_broadcast_func(dev);

  
  		/*
  		 * Clear the broadcast bit if the CPU is not in
  		 * periodic broadcast on state.
  		 */
  		if (!cpumask_test_cpu(cpu, tick_broadcast_on))
  			cpumask_clear_cpu(cpu, tick_broadcast_mask);
  
  		switch (tick_broadcast_device.mode) {
  		case TICKDEV_MODE_ONESHOT:
  			/*
  			 * If the system is in oneshot mode we can
  			 * unconditionally clear the oneshot mask bit,
  			 * because the CPU is running and therefore
  			 * not in an idle state which causes the power
  			 * state affected device to stop. Let the
  			 * caller initialize the device.
  			 */
  			tick_broadcast_clear_oneshot(cpu);
  			ret = 0;
  			break;
  
  		case TICKDEV_MODE_PERIODIC:
  			/*
  			 * If the system is in periodic mode, check
  			 * whether the broadcast device can be
  			 * switched off now.
  			 */
  			if (cpumask_empty(tick_broadcast_mask) && bc)
  				clockevents_shutdown(bc);
  			/*
  			 * If we kept the cpu in the broadcast mask,
  			 * tell the caller to leave the per cpu device
  			 * in shutdown state. The periodic interrupt

  			 * is delivered by the broadcast device, if
  			 * the broadcast device exists and is not
  			 * hrtimer based.

  			 */

  			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
  				ret = cpumask_test_cpu(cpu, tick_broadcast_mask);

  			break;
  		default:

  			break;

  		}
  	}

  	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);

  	return ret;
  }

  #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
  int tick_receive_broadcast(void)
  {
  	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
  	struct clock_event_device *evt = td->evtdev;
  
  	if (!evt)
  		return -ENODEV;
  
  	if (!evt->event_handler)
  		return -EINVAL;
  
  	evt->event_handler(evt);
  	return 0;
  }
  #endif

  /*

   * Broadcast the event to the cpus, which are set in the mask (mangled).

   */

  static bool tick_do_broadcast(struct cpumask *mask)

  {

  	int cpu = smp_processor_id();

  	struct tick_device *td;

  	bool local = false;

  
  	/*
  	 * Check, if the current cpu is in the mask
  	 */

  	if (cpumask_test_cpu(cpu, mask)) {

  		struct clock_event_device *bc = tick_broadcast_device.evtdev;

  		cpumask_clear_cpu(cpu, mask);

  		/*
  		 * We only run the local handler, if the broadcast
  		 * device is not hrtimer based. Otherwise we run into
  		 * a hrtimer recursion.
  		 *
  		 * local timer_interrupt()
  		 *   local_handler()
  		 *     expire_hrtimers()
  		 *       bc_handler()
  		 *         local_handler()
  		 *	     expire_hrtimers()
  		 */
  		local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);

  	}

  	if (!cpumask_empty(mask)) {

  		/*
  		 * It might be necessary to actually check whether the devices
  		 * have different broadcast functions. For now, just use the
  		 * one of the first device. This works as long as we have this
  		 * misfeature only on x86 (lapic)
  		 */

  		td = &per_cpu(tick_cpu_device, cpumask_first(mask));
  		td->evtdev->broadcast(mask);

  	}

  	return local;

  }
  
  /*
   * Periodic broadcast:
   * - invoke the broadcast handlers
   */

  static bool tick_do_periodic_broadcast(void)

  {

  	cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);

  	return tick_do_broadcast(tmpmask);

  }
  
  /*
   * Event handler for periodic broadcast ticks
   */
  static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
  {

  	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
  	bool bc_local;

  	raw_spin_lock(&tick_broadcast_lock);

  
  	/* Handle spurious interrupts gracefully */
  	if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
  		raw_spin_unlock(&tick_broadcast_lock);
  		return;
  	}

  	bc_local = tick_do_periodic_broadcast();

  	if (clockevent_state_oneshot(dev)) {

  		ktime_t next = ktime_add(dev->next_event, tick_period);

  		clockevents_program_event(dev, next, true);
  	}
  	raw_spin_unlock(&tick_broadcast_lock);

  
  	/*

  	 * We run the handler of the local cpu after dropping
  	 * tick_broadcast_lock because the handler might deadlock when
  	 * trying to switch to oneshot mode.

  	 */

  	if (bc_local)
  		td->evtdev->event_handler(td->evtdev);

  }

  /**
   * tick_broadcast_control - Enable/disable or force broadcast mode
   * @mode:	The selected broadcast mode
   *
   * Called when the system enters a state where affected tick devices
   * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.

   */

  void tick_broadcast_control(enum tick_broadcast_mode mode)

  {
  	struct clock_event_device *bc, *dev;
  	struct tick_device *td;

  	int cpu, bc_stopped;

  	unsigned long flags;

  	/* Protects also the local clockevent device. */
  	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

  	td = this_cpu_ptr(&tick_cpu_device);

  	dev = td->evtdev;

  
  	/*

  	 * Is the device not affected by the powerstate ?

  	 */

  	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))

  		goto out;

  	if (!tick_device_is_functional(dev))

  		goto out;

  	cpu = smp_processor_id();
  	bc = tick_broadcast_device.evtdev;

  	bc_stopped = cpumask_empty(tick_broadcast_mask);

  	switch (mode) {
  	case TICK_BROADCAST_FORCE:
  		tick_broadcast_forced = 1;

  		/* fall through */

  	case TICK_BROADCAST_ON:

  		cpumask_set_cpu(cpu, tick_broadcast_on);

  		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {

  			/*
  			 * Only shutdown the cpu local device, if:
  			 *
  			 * - the broadcast device exists
  			 * - the broadcast device is not a hrtimer based one
  			 * - the broadcast device is in periodic mode to
  			 *   avoid a hickup during switch to oneshot mode
  			 */
  			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
  			    tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)

  				clockevents_shutdown(dev);

  		}

  		break;

  
  	case TICK_BROADCAST_OFF:
  		if (tick_broadcast_forced)

  			break;
  		cpumask_clear_cpu(cpu, tick_broadcast_on);

  		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {

  			if (tick_broadcast_device.mode ==
  			    TICKDEV_MODE_PERIODIC)

  				tick_setup_periodic(dev, 0);
  		}

  		break;

  	}

  	if (bc) {
  		if (cpumask_empty(tick_broadcast_mask)) {
  			if (!bc_stopped)
  				clockevents_shutdown(bc);
  		} else if (bc_stopped) {
  			if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
  				tick_broadcast_start_periodic(bc);
  			else
  				tick_broadcast_setup_oneshot(bc);
  		}

  	}

  out:
  	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);

  }

  EXPORT_SYMBOL_GPL(tick_broadcast_control);

  
  /*
   * Set the periodic handler depending on broadcast on/off
   */
  void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
  {
  	if (!broadcast)
  		dev->event_handler = tick_handle_periodic;
  	else
  		dev->event_handler = tick_handle_periodic_broadcast;
  }

  #ifdef CONFIG_HOTPLUG_CPU

  static void tick_shutdown_broadcast(void)

  {

  	struct clock_event_device *bc = tick_broadcast_device.evtdev;

  
  	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {

  		if (bc && cpumask_empty(tick_broadcast_mask))

  			clockevents_shutdown(bc);

  	}

  }

  /*
   * Remove a CPU from broadcasting
   */
  void tick_broadcast_offline(unsigned int cpu)
  {
  	raw_spin_lock(&tick_broadcast_lock);
  	cpumask_clear_cpu(cpu, tick_broadcast_mask);
  	cpumask_clear_cpu(cpu, tick_broadcast_on);
  	tick_broadcast_oneshot_offline(cpu);
  	tick_shutdown_broadcast();
  	raw_spin_unlock(&tick_broadcast_lock);

  }

  #endif

  void tick_suspend_broadcast(void)
  {
  	struct clock_event_device *bc;
  	unsigned long flags;

  	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

  
  	bc = tick_broadcast_device.evtdev;

  	if (bc)

  		clockevents_shutdown(bc);

  	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);

  }

  /*
   * This is called from tick_resume_local() on a resuming CPU. That's
   * called from the core resume function, tick_unfreeze() and the magic XEN
   * resume hackery.
   *
   * In none of these cases the broadcast device mode can change and the
   * bit of the resuming CPU in the broadcast mask is safe as well.
   */
  bool tick_resume_check_broadcast(void)
  {
  	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
  		return false;
  	else
  		return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
  }
  
  void tick_resume_broadcast(void)

  {
  	struct clock_event_device *bc;
  	unsigned long flags;

  	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

  
  	bc = tick_broadcast_device.evtdev;

  	if (bc) {

  		clockevents_tick_resume(bc);

  		switch (tick_broadcast_device.mode) {
  		case TICKDEV_MODE_PERIODIC:

  			if (!cpumask_empty(tick_broadcast_mask))

  				tick_broadcast_start_periodic(bc);

  			break;
  		case TICKDEV_MODE_ONESHOT:

  			if (!cpumask_empty(tick_broadcast_mask))

  				tick_resume_broadcast_oneshot(bc);

  			break;
  		}

  	}

  	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);

  }

  #ifdef CONFIG_TICK_ONESHOT

  static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
  static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
  static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;

  /*

   * Exposed for debugging: see timer_list.c

   */

  struct cpumask *tick_get_broadcast_oneshot_mask(void)

  {

  	return tick_broadcast_oneshot_mask;

  }

  /*

   * Called before going idle with interrupts disabled. Checks whether a
   * broadcast event from the other core is about to happen. We detected
   * that in tick_broadcast_oneshot_control(). The callsite can use this
   * to avoid a deep idle transition as we are about to get the
   * broadcast IPI right away.
   */
  int tick_check_broadcast_expired(void)
  {
  	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
  }
  
  /*

   * Set broadcast interrupt affinity
   */
  static void tick_broadcast_set_affinity(struct clock_event_device *bc,
  					const struct cpumask *cpumask)
  {
  	if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
  		return;
  
  	if (cpumask_equal(bc->cpumask, cpumask))
  		return;
  
  	bc->cpumask = cpumask;
  	irq_set_affinity(bc->irq, bc->cpumask);
  }

  static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
  				     ktime_t expires)

  {

  	if (!clockevent_state_oneshot(bc))

  		clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);

  	clockevents_program_event(bc, expires, 1);
  	tick_broadcast_set_affinity(bc, cpumask_of(cpu));

  }

  static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)

  {

  	clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);

  }

  /*

   * Called from irq_enter() when idle was interrupted to reenable the
   * per cpu device.
   */

  void tick_check_oneshot_broadcast_this_cpu(void)

  {

  	if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {

  		struct tick_device *td = this_cpu_ptr(&tick_cpu_device);

  		/*
  		 * We might be in the middle of switching over from
  		 * periodic to oneshot. If the CPU has not yet
  		 * switched over, leave the device alone.
  		 */
  		if (td->mode == TICKDEV_MODE_ONESHOT) {

  			clockevents_switch_state(td->evtdev,

  					      CLOCK_EVT_STATE_ONESHOT);

  		}

  	}
  }
  
  /*

   * Handle oneshot mode broadcasting
   */
  static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
  {
  	struct tick_device *td;

  	ktime_t now, next_event;

  	int cpu, next_cpu = 0;

  	bool bc_local;

  	raw_spin_lock(&tick_broadcast_lock);

  	dev->next_event = KTIME_MAX;
  	next_event = KTIME_MAX;

  	cpumask_clear(tmpmask);

  	now = ktime_get();
  	/* Find all expired events */

  	for_each_cpu(cpu, tick_broadcast_oneshot_mask) {

  		/*
  		 * Required for !SMP because for_each_cpu() reports
  		 * unconditionally CPU0 as set on UP kernels.
  		 */
  		if (!IS_ENABLED(CONFIG_SMP) &&
  		    cpumask_empty(tick_broadcast_oneshot_mask))
  			break;

  		td = &per_cpu(tick_cpu_device, cpu);

  		if (td->evtdev->next_event <= now) {

  			cpumask_set_cpu(cpu, tmpmask);

  			/*
  			 * Mark the remote cpu in the pending mask, so
  			 * it can avoid reprogramming the cpu local
  			 * timer in tick_broadcast_oneshot_control().
  			 */
  			cpumask_set_cpu(cpu, tick_broadcast_pending_mask);

  		} else if (td->evtdev->next_event < next_event) {
  			next_event = td->evtdev->next_event;

  			next_cpu = cpu;
  		}

  	}

  	/*
  	 * Remove the current cpu from the pending mask. The event is
  	 * delivered immediately in tick_do_broadcast() !
  	 */
  	cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);

  	/* Take care of enforced broadcast requests */
  	cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
  	cpumask_clear(tick_broadcast_force_mask);

  	/*

  	 * Sanity check. Catch the case where we try to broadcast to
  	 * offline cpus.
  	 */
  	if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
  		cpumask_and(tmpmask, tmpmask, cpu_online_mask);
  
  	/*

  	 * Wakeup the cpus which have an expired event.

  	 */

  	bc_local = tick_do_broadcast(tmpmask);

  
  	/*
  	 * Two reasons for reprogram:
  	 *
  	 * - The global event did not expire any CPU local
  	 * events. This happens in dyntick mode, as the maximum PIT
  	 * delta is quite small.
  	 *
  	 * - There are pending events on sleeping CPUs which were not
  	 * in the event mask

  	 */

  	if (next_event != KTIME_MAX)

  		tick_broadcast_set_event(dev, next_cpu, next_event);

  	raw_spin_unlock(&tick_broadcast_lock);

  
  	if (bc_local) {
  		td = this_cpu_ptr(&tick_cpu_device);
  		td->evtdev->event_handler(td->evtdev);
  	}

  }

  static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
  {
  	if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
  		return 0;

  	if (bc->next_event == KTIME_MAX)

  		return 0;
  	return bc->bound_on == cpu ? -EBUSY : 0;
  }
  
  static void broadcast_shutdown_local(struct clock_event_device *bc,
  				     struct clock_event_device *dev)
  {
  	/*
  	 * For hrtimer based broadcasting we cannot shutdown the cpu
  	 * local device if our own event is the first one to expire or
  	 * if we own the broadcast timer.
  	 */
  	if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
  		if (broadcast_needs_cpu(bc, smp_processor_id()))
  			return;

  		if (dev->next_event < bc->next_event)

  			return;
  	}

  	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);

  }

  int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)

  {
  	struct clock_event_device *bc, *dev;

  	int cpu, ret = 0;

  	ktime_t now;

  	/*

  	 * If there is no broadcast device, tell the caller not to go
  	 * into deep idle.
  	 */
  	if (!tick_broadcast_device.evtdev)
  		return -EBUSY;

  	dev = this_cpu_ptr(&tick_cpu_device)->evtdev;

  	raw_spin_lock(&tick_broadcast_lock);

  	bc = tick_broadcast_device.evtdev;

  	cpu = smp_processor_id();

  	if (state == TICK_BROADCAST_ENTER) {

  		/*

  		 * If the current CPU owns the hrtimer broadcast
  		 * mechanism, it cannot go deep idle and we do not add
  		 * the CPU to the broadcast mask. We don't have to go
  		 * through the EXIT path as the local timer is not
  		 * shutdown.
  		 */
  		ret = broadcast_needs_cpu(bc, cpu);
  		if (ret)
  			goto out;
  
  		/*

  		 * If the broadcast device is in periodic mode, we
  		 * return.
  		 */

  		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
  			/* If it is a hrtimer based broadcast, return busy */
  			if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
  				ret = -EBUSY;

  			goto out;

  		}

  		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {

  			WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));

  
  			/* Conditionally shut down the local timer. */

  			broadcast_shutdown_local(bc, dev);

  			/*
  			 * We only reprogram the broadcast timer if we
  			 * did not mark ourself in the force mask and
  			 * if the cpu local event is earlier than the
  			 * broadcast event. If the current CPU is in
  			 * the force mask, then we are going to be

  			 * woken by the IPI right away; we return
  			 * busy, so the CPU does not try to go deep
  			 * idle.

  			 */

  			if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
  				ret = -EBUSY;

  			} else if (dev->next_event < bc->next_event) {

  				tick_broadcast_set_event(bc, cpu, dev->next_event);

  				/*
  				 * In case of hrtimer broadcasts the
  				 * programming might have moved the
  				 * timer to this cpu. If yes, remove
  				 * us from the broadcast mask and
  				 * return busy.
  				 */
  				ret = broadcast_needs_cpu(bc, cpu);
  				if (ret) {
  					cpumask_clear_cpu(cpu,
  						tick_broadcast_oneshot_mask);
  				}

  			}

  		}
  	} else {

  		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {

  			clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);

  			/*
  			 * The cpu which was handling the broadcast
  			 * timer marked this cpu in the broadcast
  			 * pending mask and fired the broadcast
  			 * IPI. So we are going to handle the expired
  			 * event anyway via the broadcast IPI
  			 * handler. No need to reprogram the timer
  			 * with an already expired event.
  			 */
  			if (cpumask_test_and_clear_cpu(cpu,
  				       tick_broadcast_pending_mask))
  				goto out;

  			/*

  			 * Bail out if there is no next event.
  			 */

  			if (dev->next_event == KTIME_MAX)

  				goto out;
  			/*

  			 * If the pending bit is not set, then we are
  			 * either the CPU handling the broadcast
  			 * interrupt or we got woken by something else.
  			 *

  			 * We are no longer in the broadcast mask, so

  			 * if the cpu local expiry time is already
  			 * reached, we would reprogram the cpu local
  			 * timer with an already expired event.
  			 *
  			 * This can lead to a ping-pong when we return

  			 * to idle and therefore rearm the broadcast

  			 * timer before the cpu local timer was able
  			 * to fire. This happens because the forced
  			 * reprogramming makes sure that the event
  			 * will happen in the future and depending on
  			 * the min_delta setting this might be far
  			 * enough out that the ping-pong starts.
  			 *
  			 * If the cpu local next_event has expired
  			 * then we know that the broadcast timer
  			 * next_event has expired as well and
  			 * broadcast is about to be handled. So we
  			 * avoid reprogramming and enforce that the
  			 * broadcast handler, which did not run yet,
  			 * will invoke the cpu local handler.
  			 *
  			 * We cannot call the handler directly from
  			 * here, because we might be in a NOHZ phase
  			 * and we did not go through the irq_enter()
  			 * nohz fixups.
  			 */
  			now = ktime_get();

  			if (dev->next_event <= now) {

  				cpumask_set_cpu(cpu, tick_broadcast_force_mask);
  				goto out;
  			}
  			/*
  			 * We got woken by something else. Reprogram
  			 * the cpu local timer device.
  			 */

  			tick_program_event(dev->next_event, 1);

  		}
  	}

  out:

  	raw_spin_unlock(&tick_broadcast_lock);

  	return ret;

  }

  /*
   * Reset the one shot broadcast for a cpu
   *
   * Called with tick_broadcast_lock held
   */
  static void tick_broadcast_clear_oneshot(int cpu)
  {

  	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);

  	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);

  }

  static void tick_broadcast_init_next_event(struct cpumask *mask,
  					   ktime_t expires)

  {
  	struct tick_device *td;
  	int cpu;

  	for_each_cpu(cpu, mask) {

  		td = &per_cpu(tick_cpu_device, cpu);
  		if (td->evtdev)
  			td->evtdev->next_event = expires;
  	}
  }

  /**

   * tick_broadcast_setup_oneshot - setup the broadcast device

   */

  static void tick_broadcast_setup_oneshot(struct clock_event_device *bc)

  {

  	int cpu = smp_processor_id();

  	if (!bc)
  		return;

  	/* Set it up only once ! */
  	if (bc->event_handler != tick_handle_oneshot_broadcast) {

  		int was_periodic = clockevent_state_periodic(bc);

  		bc->event_handler = tick_handle_oneshot_broadcast;

  		/*
  		 * We must be careful here. There might be other CPUs
  		 * waiting for periodic broadcast. We need to set the
  		 * oneshot_mask bits for those and program the
  		 * broadcast device to fire.
  		 */

  		cpumask_copy(tmpmask, tick_broadcast_mask);
  		cpumask_clear_cpu(cpu, tmpmask);
  		cpumask_or(tick_broadcast_oneshot_mask,
  			   tick_broadcast_oneshot_mask, tmpmask);

  		if (was_periodic && !cpumask_empty(tmpmask)) {

  			clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);

  			tick_broadcast_init_next_event(tmpmask,

  						       tick_next_period);

  			tick_broadcast_set_event(bc, cpu, tick_next_period);

  		} else

  			bc->next_event = KTIME_MAX;

  	} else {
  		/*
  		 * The first cpu which switches to oneshot mode sets
  		 * the bit for all other cpus which are in the general
  		 * (periodic) broadcast mask. So the bit is set and
  		 * would prevent the first broadcast enter after this
  		 * to program the bc device.
  		 */
  		tick_broadcast_clear_oneshot(cpu);

  	}

  }
  
  /*
   * Select oneshot operating mode for the broadcast device
   */
  void tick_broadcast_switch_to_oneshot(void)
  {
  	struct clock_event_device *bc;
  	unsigned long flags;

  	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

  
  	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;

  	bc = tick_broadcast_device.evtdev;
  	if (bc)
  		tick_broadcast_setup_oneshot(bc);

  	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);

  }

  #ifdef CONFIG_HOTPLUG_CPU
  void hotplug_cpu__broadcast_tick_pull(int deadcpu)
  {
  	struct clock_event_device *bc;
  	unsigned long flags;
  
  	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
  	bc = tick_broadcast_device.evtdev;
  
  	if (bc && broadcast_needs_cpu(bc, deadcpu)) {
  		/* This moves the broadcast assignment to this CPU: */
  		clockevents_program_event(bc, bc->next_event, 1);
  	}
  	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
  }

  
  /*

   * Remove a dying CPU from broadcasting

   */

  static void tick_broadcast_oneshot_offline(unsigned int cpu)

  {

  	/*

  	 * Clear the broadcast masks for the dead cpu, but do not stop
  	 * the broadcast device!

  	 */

  	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);

  	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
  	cpumask_clear_cpu(cpu, tick_broadcast_force_mask);

  }

  #endif

  /*
   * Check, whether the broadcast device is in one shot mode
   */
  int tick_broadcast_oneshot_active(void)
  {
  	return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
  }

  /*
   * Check whether the broadcast device supports oneshot.
   */
  bool tick_broadcast_oneshot_available(void)
  {
  	struct clock_event_device *bc = tick_broadcast_device.evtdev;
  
  	return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
  }

  #else
  int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
  {
  	struct clock_event_device *bc = tick_broadcast_device.evtdev;
  
  	if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
  		return -EBUSY;
  
  	return 0;
  }

  #endif

  
  void __init tick_broadcast_init(void)
  {

  	zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);

  	zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);

  	zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);

  #ifdef CONFIG_TICK_ONESHOT

  	zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
  	zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
  	zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);

  #endif
  }