/*
   * linux/kernel/irq/manage.c
   *

   * Copyright (C) 1992, 1998-2006 Linus Torvalds, Ingo Molnar
   * Copyright (C) 2005-2006 Thomas Gleixner

   *
   * This file contains driver APIs to the irq subsystem.
   */
  
  #include <linux/irq.h>

  #include <linux/kthread.h>

  #include <linux/module.h>
  #include <linux/random.h>
  #include <linux/interrupt.h>

  #include <linux/slab.h>

  #include <linux/sched.h>

  
  #include "internals.h"

  #ifdef CONFIG_IRQ_FORCED_THREADING
  __read_mostly bool force_irqthreads;
  
  static int __init setup_forced_irqthreads(char *arg)
  {
  	force_irqthreads = true;
  	return 0;
  }
  early_param("threadirqs", setup_forced_irqthreads);
  #endif

  /**
   *	synchronize_irq - wait for pending IRQ handlers (on other CPUs)

   *	@irq: interrupt number to wait for

   *
   *	This function waits for any pending IRQ handlers for this interrupt
   *	to complete before returning. If you use this function while
   *	holding a resource the IRQ handler may need you will deadlock.
   *
   *	This function may be called - with care - from IRQ context.
   */
  void synchronize_irq(unsigned int irq)
  {

  	struct irq_desc *desc = irq_to_desc(irq);

  	bool inprogress;

  	if (!desc)

  		return;

  	do {
  		unsigned long flags;
  
  		/*
  		 * Wait until we're out of the critical section.  This might
  		 * give the wrong answer due to the lack of memory barriers.
  		 */

  		while (irqd_irq_inprogress(&desc->irq_data))

  			cpu_relax();
  
  		/* Ok, that indicated we're done: double-check carefully. */

  		raw_spin_lock_irqsave(&desc->lock, flags);

  		inprogress = irqd_irq_inprogress(&desc->irq_data);

  		raw_spin_unlock_irqrestore(&desc->lock, flags);

  
  		/* Oops, that failed? */

  	} while (inprogress);

  
  	/*
  	 * We made sure that no hardirq handler is running. Now verify
  	 * that no threaded handlers are active.
  	 */
  	wait_event(desc->wait_for_threads, !atomic_read(&desc->threads_active));

  }

  EXPORT_SYMBOL(synchronize_irq);

  #ifdef CONFIG_SMP
  cpumask_var_t irq_default_affinity;

  /**
   *	irq_can_set_affinity - Check if the affinity of a given irq can be set
   *	@irq:		Interrupt to check
   *
   */
  int irq_can_set_affinity(unsigned int irq)
  {

  	struct irq_desc *desc = irq_to_desc(irq);

  	if (!desc || !irqd_can_balance(&desc->irq_data) ||
  	    !desc->irq_data.chip || !desc->irq_data.chip->irq_set_affinity)

  		return 0;
  
  	return 1;
  }

  /**
   *	irq_set_thread_affinity - Notify irq threads to adjust affinity
   *	@desc:		irq descriptor which has affitnity changed
   *
   *	We just set IRQTF_AFFINITY and delegate the affinity setting
   *	to the interrupt thread itself. We can not call
   *	set_cpus_allowed_ptr() here as we hold desc->lock and this
   *	code can be called from hard interrupt context.
   */
  void irq_set_thread_affinity(struct irq_desc *desc)

  {
  	struct irqaction *action = desc->action;
  
  	while (action) {
  		if (action->thread)

  			set_bit(IRQTF_AFFINITY, &action->thread_flags);

  		action = action->next;
  	}
  }

  #ifdef CONFIG_GENERIC_PENDING_IRQ

  static inline bool irq_can_move_pcntxt(struct irq_data *data)

  {

  	return irqd_can_move_in_process_context(data);

  }

  static inline bool irq_move_pending(struct irq_data *data)

  {

  	return irqd_is_setaffinity_pending(data);

  }
  static inline void
  irq_copy_pending(struct irq_desc *desc, const struct cpumask *mask)
  {
  	cpumask_copy(desc->pending_mask, mask);
  }
  static inline void
  irq_get_pending(struct cpumask *mask, struct irq_desc *desc)
  {
  	cpumask_copy(mask, desc->pending_mask);
  }
  #else

  static inline bool irq_can_move_pcntxt(struct irq_data *data) { return true; }

  static inline bool irq_move_pending(struct irq_data *data) { return false; }

  static inline void
  irq_copy_pending(struct irq_desc *desc, const struct cpumask *mask) { }
  static inline void
  irq_get_pending(struct cpumask *mask, struct irq_desc *desc) { }
  #endif

  int __irq_set_affinity_locked(struct irq_data *data, const struct cpumask *mask)

  {

  	struct irq_chip *chip = irq_data_get_irq_chip(data);
  	struct irq_desc *desc = irq_data_to_desc(data);

  	int ret = 0;

  	if (!chip || !chip->irq_set_affinity)

  		return -EINVAL;

  	if (irq_can_move_pcntxt(data)) {

  		ret = chip->irq_set_affinity(data, mask, false);

  		switch (ret) {
  		case IRQ_SET_MASK_OK:

  			cpumask_copy(data->affinity, mask);

  		case IRQ_SET_MASK_OK_NOCOPY:

  			irq_set_thread_affinity(desc);

  			ret = 0;

  		}

  	} else {

  		irqd_set_move_pending(data);

  		irq_copy_pending(desc, mask);

  	}

  	if (desc->affinity_notify) {
  		kref_get(&desc->affinity_notify->kref);
  		schedule_work(&desc->affinity_notify->work);
  	}

  	irqd_set(data, IRQD_AFFINITY_SET);
  
  	return ret;
  }
  
  /**
   *	irq_set_affinity - Set the irq affinity of a given irq
   *	@irq:		Interrupt to set affinity

   *	@mask:		cpumask

   *
   */
  int irq_set_affinity(unsigned int irq, const struct cpumask *mask)
  {
  	struct irq_desc *desc = irq_to_desc(irq);
  	unsigned long flags;
  	int ret;
  
  	if (!desc)
  		return -EINVAL;
  
  	raw_spin_lock_irqsave(&desc->lock, flags);
  	ret =  __irq_set_affinity_locked(irq_desc_get_irq_data(desc), mask);

  	raw_spin_unlock_irqrestore(&desc->lock, flags);

  	return ret;

  }

  int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
  {

  	unsigned long flags;

  	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);

  
  	if (!desc)
  		return -EINVAL;

  	desc->affinity_hint = m;

  	irq_put_desc_unlock(desc, flags);

  	return 0;
  }
  EXPORT_SYMBOL_GPL(irq_set_affinity_hint);

  static void irq_affinity_notify(struct work_struct *work)
  {
  	struct irq_affinity_notify *notify =
  		container_of(work, struct irq_affinity_notify, work);
  	struct irq_desc *desc = irq_to_desc(notify->irq);
  	cpumask_var_t cpumask;
  	unsigned long flags;

  	if (!desc || !alloc_cpumask_var(&cpumask, GFP_KERNEL))

  		goto out;
  
  	raw_spin_lock_irqsave(&desc->lock, flags);

  	if (irq_move_pending(&desc->irq_data))

  		irq_get_pending(cpumask, desc);

  	else

  		cpumask_copy(cpumask, desc->irq_data.affinity);

  	raw_spin_unlock_irqrestore(&desc->lock, flags);
  
  	notify->notify(notify, cpumask);
  
  	free_cpumask_var(cpumask);
  out:
  	kref_put(&notify->kref, notify->release);
  }
  
  /**
   *	irq_set_affinity_notifier - control notification of IRQ affinity changes
   *	@irq:		Interrupt for which to enable/disable notification
   *	@notify:	Context for notification, or %NULL to disable
   *			notification.  Function pointers must be initialised;
   *			the other fields will be initialised by this function.
   *
   *	Must be called in process context.  Notification may only be enabled
   *	after the IRQ is allocated and must be disabled before the IRQ is
   *	freed using free_irq().
   */
  int
  irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
  {
  	struct irq_desc *desc = irq_to_desc(irq);
  	struct irq_affinity_notify *old_notify;
  	unsigned long flags;
  
  	/* The release function is promised process context */
  	might_sleep();
  
  	if (!desc)
  		return -EINVAL;
  
  	/* Complete initialisation of *notify */
  	if (notify) {
  		notify->irq = irq;
  		kref_init(&notify->kref);
  		INIT_WORK(&notify->work, irq_affinity_notify);
  	}
  
  	raw_spin_lock_irqsave(&desc->lock, flags);
  	old_notify = desc->affinity_notify;
  	desc->affinity_notify = notify;
  	raw_spin_unlock_irqrestore(&desc->lock, flags);
  
  	if (old_notify)
  		kref_put(&old_notify->kref, old_notify->release);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(irq_set_affinity_notifier);

  #ifndef CONFIG_AUTO_IRQ_AFFINITY
  /*
   * Generic version of the affinity autoselector.
   */

  static int
  setup_affinity(unsigned int irq, struct irq_desc *desc, struct cpumask *mask)

  {

  	struct irq_chip *chip = irq_desc_get_chip(desc);

  	struct cpumask *set = irq_default_affinity;

  	int ret;

  	/* Excludes PER_CPU and NO_BALANCE interrupts */

  	if (!irq_can_set_affinity(irq))
  		return 0;

  	/*
  	 * Preserve an userspace affinity setup, but make sure that
  	 * one of the targets is online.
  	 */

  	if (irqd_has_set(&desc->irq_data, IRQD_AFFINITY_SET)) {

  		if (cpumask_intersects(desc->irq_data.affinity,
  				       cpu_online_mask))
  			set = desc->irq_data.affinity;

  		else

  			irqd_clear(&desc->irq_data, IRQD_AFFINITY_SET);

  	}

  	cpumask_and(mask, cpu_online_mask, set);
  	ret = chip->irq_set_affinity(&desc->irq_data, mask, false);
  	switch (ret) {
  	case IRQ_SET_MASK_OK:
  		cpumask_copy(desc->irq_data.affinity, mask);
  	case IRQ_SET_MASK_OK_NOCOPY:
  		irq_set_thread_affinity(desc);
  	}

  	return 0;
  }

  #else

  static inline int
  setup_affinity(unsigned int irq, struct irq_desc *d, struct cpumask *mask)

  {
  	return irq_select_affinity(irq);
  }

  #endif

  /*
   * Called when affinity is set via /proc/irq
   */

  int irq_select_affinity_usr(unsigned int irq, struct cpumask *mask)

  {
  	struct irq_desc *desc = irq_to_desc(irq);
  	unsigned long flags;
  	int ret;

  	raw_spin_lock_irqsave(&desc->lock, flags);

  	ret = setup_affinity(irq, desc, mask);

  	raw_spin_unlock_irqrestore(&desc->lock, flags);

  	return ret;
  }
  
  #else

  static inline int
  setup_affinity(unsigned int irq, struct irq_desc *desc, struct cpumask *mask)

  {
  	return 0;
  }

  #endif

  void __disable_irq(struct irq_desc *desc, unsigned int irq, bool suspend)
  {
  	if (suspend) {

  		if (!desc->action || (desc->action->flags & IRQF_NO_SUSPEND))

  			return;

  		desc->istate |= IRQS_SUSPENDED;

  	}

  	if (!desc->depth++)

  		irq_disable(desc);

  }

  static int __disable_irq_nosync(unsigned int irq)
  {
  	unsigned long flags;

  	struct irq_desc *desc = irq_get_desc_buslock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);

  
  	if (!desc)
  		return -EINVAL;
  	__disable_irq(desc, irq, false);
  	irq_put_desc_busunlock(desc, flags);
  	return 0;
  }

  /**
   *	disable_irq_nosync - disable an irq without waiting
   *	@irq: Interrupt to disable
   *
   *	Disable the selected interrupt line.  Disables and Enables are
   *	nested.
   *	Unlike disable_irq(), this function does not ensure existing
   *	instances of the IRQ handler have completed before returning.
   *
   *	This function may be called from IRQ context.
   */
  void disable_irq_nosync(unsigned int irq)
  {

  	__disable_irq_nosync(irq);

  }

  EXPORT_SYMBOL(disable_irq_nosync);
  
  /**
   *	disable_irq - disable an irq and wait for completion
   *	@irq: Interrupt to disable
   *
   *	Disable the selected interrupt line.  Enables and Disables are
   *	nested.
   *	This function waits for any pending IRQ handlers for this interrupt
   *	to complete before returning. If you use this function while
   *	holding a resource the IRQ handler may need you will deadlock.
   *
   *	This function may be called - with care - from IRQ context.
   */
  void disable_irq(unsigned int irq)
  {

  	if (!__disable_irq_nosync(irq))

  		synchronize_irq(irq);
  }

  EXPORT_SYMBOL(disable_irq);

  void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume)

  {

  	if (resume) {

  		if (!(desc->istate & IRQS_SUSPENDED)) {

  			if (!desc->action)
  				return;
  			if (!(desc->action->flags & IRQF_FORCE_RESUME))
  				return;
  			/* Pretend that it got disabled ! */
  			desc->depth++;
  		}

  		desc->istate &= ~IRQS_SUSPENDED;

  	}

  	switch (desc->depth) {
  	case 0:

   err_out:

  		WARN(1, KERN_WARNING "Unbalanced enable for IRQ %d
  ", irq);

  		break;
  	case 1: {

  		if (desc->istate & IRQS_SUSPENDED)

  			goto err_out;

  		/* Prevent probing on this irq: */

  		irq_settings_set_noprobe(desc);

  		irq_enable(desc);

  		check_irq_resend(desc, irq);
  		/* fall-through */
  	}
  	default:
  		desc->depth--;
  	}
  }

  /**
   *	enable_irq - enable handling of an irq
   *	@irq: Interrupt to enable
   *
   *	Undoes the effect of one call to disable_irq().  If this
   *	matches the last disable, processing of interrupts on this
   *	IRQ line is re-enabled.
   *

   *	This function may be called from IRQ context only when

   *	desc->irq_data.chip->bus_lock and desc->chip->bus_sync_unlock are NULL !

   */
  void enable_irq(unsigned int irq)
  {

  	unsigned long flags;

  	struct irq_desc *desc = irq_get_desc_buslock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);

  	if (!desc)

  		return;

  	if (WARN(!desc->irq_data.chip,
  		 KERN_ERR "enable_irq before setup/request_irq: irq %u
  ", irq))

  		goto out;

  	__enable_irq(desc, irq, false);

  out:
  	irq_put_desc_busunlock(desc, flags);

  }

  EXPORT_SYMBOL(enable_irq);

  static int set_irq_wake_real(unsigned int irq, unsigned int on)

  {

  	struct irq_desc *desc = irq_to_desc(irq);

  	int ret = -ENXIO;

  	if (irq_desc_get_chip(desc)->flags &  IRQCHIP_SKIP_SET_WAKE)
  		return 0;

  	if (desc->irq_data.chip->irq_set_wake)
  		ret = desc->irq_data.chip->irq_set_wake(&desc->irq_data, on);

  
  	return ret;
  }

  /**

   *	irq_set_irq_wake - control irq power management wakeup

   *	@irq:	interrupt to control
   *	@on:	enable/disable power management wakeup
   *

   *	Enable/disable power management wakeup mode, which is
   *	disabled by default.  Enables and disables must match,
   *	just as they match for non-wakeup mode support.
   *
   *	Wakeup mode lets this IRQ wake the system from sleep
   *	states like "suspend to RAM".

   */

  int irq_set_irq_wake(unsigned int irq, unsigned int on)

  {

  	unsigned long flags;

  	struct irq_desc *desc = irq_get_desc_buslock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);

  	int ret = 0;

  	if (!desc)
  		return -EINVAL;

  	/* wakeup-capable irqs can be shared between drivers that
  	 * don't need to have the same sleep mode behaviors.
  	 */

  	if (on) {

  		if (desc->wake_depth++ == 0) {
  			ret = set_irq_wake_real(irq, on);
  			if (ret)
  				desc->wake_depth = 0;
  			else

  				irqd_set(&desc->irq_data, IRQD_WAKEUP_STATE);

  		}

  	} else {
  		if (desc->wake_depth == 0) {

  			WARN(1, "Unbalanced IRQ %d wake disable
  ", irq);

  		} else if (--desc->wake_depth == 0) {
  			ret = set_irq_wake_real(irq, on);
  			if (ret)
  				desc->wake_depth = 1;
  			else

  				irqd_clear(&desc->irq_data, IRQD_WAKEUP_STATE);

  		}

  	}

  	irq_put_desc_busunlock(desc, flags);

  	return ret;
  }

  EXPORT_SYMBOL(irq_set_irq_wake);

  /*
   * Internal function that tells the architecture code whether a
   * particular irq has been exclusively allocated or is available
   * for driver use.
   */
  int can_request_irq(unsigned int irq, unsigned long irqflags)
  {

  	unsigned long flags;

  	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);

  	int canrequest = 0;

  	if (!desc)
  		return 0;

  	if (irq_settings_can_request(desc)) {
  		if (desc->action)
  			if (irqflags & desc->action->flags & IRQF_SHARED)
  				canrequest =1;
  	}
  	irq_put_desc_unlock(desc, flags);
  	return canrequest;

  }

  int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,

  		      unsigned long flags)

  {

  	struct irq_chip *chip = desc->irq_data.chip;

  	int ret, unmask = 0;

  	if (!chip || !chip->irq_set_type) {

  		/*
  		 * IRQF_TRIGGER_* but the PIC does not support multiple
  		 * flow-types?
  		 */

  		pr_debug("No set_type function for IRQ %d (%s)
  ", irq,

  				chip ? (chip->name ? : "unknown") : "unknown");
  		return 0;
  	}

  	flags &= IRQ_TYPE_SENSE_MASK;

  
  	if (chip->flags & IRQCHIP_SET_TYPE_MASKED) {

  		if (!irqd_irq_masked(&desc->irq_data))

  			mask_irq(desc);

  		if (!irqd_irq_disabled(&desc->irq_data))

  			unmask = 1;
  	}

  	/* caller masked out all except trigger mode flags */

  	ret = chip->irq_set_type(&desc->irq_data, flags);

  	switch (ret) {
  	case IRQ_SET_MASK_OK:
  		irqd_clear(&desc->irq_data, IRQD_TRIGGER_MASK);
  		irqd_set(&desc->irq_data, flags);
  
  	case IRQ_SET_MASK_OK_NOCOPY:
  		flags = irqd_get_trigger_type(&desc->irq_data);
  		irq_settings_set_trigger_mask(desc, flags);
  		irqd_clear(&desc->irq_data, IRQD_LEVEL);
  		irq_settings_clr_level(desc);
  		if (flags & IRQ_TYPE_LEVEL_MASK) {
  			irq_settings_set_level(desc);
  			irqd_set(&desc->irq_data, IRQD_LEVEL);
  		}

  		ret = 0;

  		break;

  	default:
  		pr_err("setting trigger mode %lu for irq %u failed (%pF)
  ",
  		       flags, irq, chip->irq_set_type);

  	}

  	if (unmask)
  		unmask_irq(desc);

  	return ret;
  }

  /*
   * Default primary interrupt handler for threaded interrupts. Is
   * assigned as primary handler when request_threaded_irq is called
   * with handler == NULL. Useful for oneshot interrupts.
   */
  static irqreturn_t irq_default_primary_handler(int irq, void *dev_id)
  {
  	return IRQ_WAKE_THREAD;
  }

  /*
   * Primary handler for nested threaded interrupts. Should never be
   * called.
   */
  static irqreturn_t irq_nested_primary_handler(int irq, void *dev_id)
  {
  	WARN(1, "Primary handler called for nested irq %d
  ", irq);
  	return IRQ_NONE;
  }

  static int irq_wait_for_interrupt(struct irqaction *action)
  {

  	set_current_state(TASK_INTERRUPTIBLE);

  	while (!kthread_should_stop()) {

  
  		if (test_and_clear_bit(IRQTF_RUNTHREAD,
  				       &action->thread_flags)) {

  			__set_current_state(TASK_RUNNING);
  			return 0;

  		}
  		schedule();

  		set_current_state(TASK_INTERRUPTIBLE);

  	}

  	__set_current_state(TASK_RUNNING);

  	return -1;
  }

  /*
   * Oneshot interrupts keep the irq line masked until the threaded
   * handler finished. unmask if the interrupt has not been disabled and
   * is marked MASKED.
   */

  static void irq_finalize_oneshot(struct irq_desc *desc,
  				 struct irqaction *action, bool force)

  {

  	if (!(desc->istate & IRQS_ONESHOT))
  		return;

  again:

  	chip_bus_lock(desc);

  	raw_spin_lock_irq(&desc->lock);

  
  	/*
  	 * Implausible though it may be we need to protect us against
  	 * the following scenario:
  	 *
  	 * The thread is faster done than the hard interrupt handler
  	 * on the other CPU. If we unmask the irq line then the
  	 * interrupt can come in again and masks the line, leaves due

  	 * to IRQS_INPROGRESS and the irq line is masked forever.

  	 *
  	 * This also serializes the state of shared oneshot handlers
  	 * versus "desc->threads_onehsot |= action->thread_mask;" in
  	 * irq_wake_thread(). See the comment there which explains the
  	 * serialization.

  	 */

  	if (unlikely(irqd_irq_inprogress(&desc->irq_data))) {

  		raw_spin_unlock_irq(&desc->lock);

  		chip_bus_sync_unlock(desc);

  		cpu_relax();
  		goto again;
  	}

  	/*
  	 * Now check again, whether the thread should run. Otherwise
  	 * we would clear the threads_oneshot bit of this thread which
  	 * was just set.
  	 */
  	if (!force && test_bit(IRQTF_RUNTHREAD, &action->thread_flags))
  		goto out_unlock;
  
  	desc->threads_oneshot &= ~action->thread_mask;

  	if (!desc->threads_oneshot && !irqd_irq_disabled(&desc->irq_data) &&
  	    irqd_irq_masked(&desc->irq_data))
  		unmask_irq(desc);

  out_unlock:

  	raw_spin_unlock_irq(&desc->lock);

  	chip_bus_sync_unlock(desc);

  }

  #ifdef CONFIG_SMP

  /*

   * Check whether we need to chasnge the affinity of the interrupt thread.

   */
  static void
  irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action)
  {
  	cpumask_var_t mask;
  
  	if (!test_and_clear_bit(IRQTF_AFFINITY, &action->thread_flags))
  		return;
  
  	/*
  	 * In case we are out of memory we set IRQTF_AFFINITY again and
  	 * try again next time
  	 */
  	if (!alloc_cpumask_var(&mask, GFP_KERNEL)) {
  		set_bit(IRQTF_AFFINITY, &action->thread_flags);
  		return;
  	}

  	raw_spin_lock_irq(&desc->lock);

  	cpumask_copy(mask, desc->irq_data.affinity);

  	raw_spin_unlock_irq(&desc->lock);

  
  	set_cpus_allowed_ptr(current, mask);
  	free_cpumask_var(mask);
  }

  #else
  static inline void
  irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action) { }
  #endif

  
  /*

   * Interrupts which are not explicitely requested as threaded
   * interrupts rely on the implicit bh/preempt disable of the hard irq
   * context. So we need to disable bh here to avoid deadlocks and other
   * side effects.
   */

  static irqreturn_t

  irq_forced_thread_fn(struct irq_desc *desc, struct irqaction *action)
  {

  	irqreturn_t ret;

  	local_bh_disable();

  	ret = action->thread_fn(action->irq, action->dev_id);

  	irq_finalize_oneshot(desc, action, false);
  	local_bh_enable();

  	return ret;

  }
  
  /*
   * Interrupts explicitely requested as threaded interupts want to be
   * preemtible - many of them need to sleep and wait for slow busses to
   * complete.
   */

  static irqreturn_t irq_thread_fn(struct irq_desc *desc,
  		struct irqaction *action)

  {

  	irqreturn_t ret;
  
  	ret = action->thread_fn(action->irq, action->dev_id);

  	irq_finalize_oneshot(desc, action, false);

  	return ret;

  }
  
  /*

   * Interrupt handler thread
   */
  static int irq_thread(void *data)
  {

  	static const struct sched_param param = {

  		.sched_priority = MAX_USER_RT_PRIO/2,
  	};

  	struct irqaction *action = data;
  	struct irq_desc *desc = irq_to_desc(action->irq);

  	irqreturn_t (*handler_fn)(struct irq_desc *desc,
  			struct irqaction *action);

  	int wake;

  	if (force_irqthreads & test_bit(IRQTF_FORCED_THREAD,
  					&action->thread_flags))
  		handler_fn = irq_forced_thread_fn;
  	else
  		handler_fn = irq_thread_fn;

  	sched_setscheduler(current, SCHED_FIFO, &param);
  	current->irqaction = action;
  
  	while (!irq_wait_for_interrupt(action)) {

  		irq_thread_check_affinity(desc, action);

  		atomic_inc(&desc->threads_active);

  		raw_spin_lock_irq(&desc->lock);

  		if (unlikely(irqd_irq_disabled(&desc->irq_data))) {

  			/*
  			 * CHECKME: We might need a dedicated
  			 * IRQ_THREAD_PENDING flag here, which
  			 * retriggers the thread in check_irq_resend()

  			 * but AFAICT IRQS_PENDING should be fine as it

  			 * retriggers the interrupt itself --- tglx
  			 */

  			desc->istate |= IRQS_PENDING;

  			raw_spin_unlock_irq(&desc->lock);

  		} else {

  			irqreturn_t action_ret;

  			raw_spin_unlock_irq(&desc->lock);

  			action_ret = handler_fn(desc, action);
  			if (!noirqdebug)
  				note_interrupt(action->irq, desc, action_ret);

  		}
  
  		wake = atomic_dec_and_test(&desc->threads_active);
  
  		if (wake && waitqueue_active(&desc->wait_for_threads))
  			wake_up(&desc->wait_for_threads);
  	}

  	/* Prevent a stale desc->threads_oneshot */
  	irq_finalize_oneshot(desc, action, true);

  	/*
  	 * Clear irqaction. Otherwise exit_irq_thread() would make
  	 * fuzz about an active irq thread going into nirvana.
  	 */
  	current->irqaction = NULL;
  	return 0;
  }
  
  /*
   * Called from do_exit()
   */
  void exit_irq_thread(void)
  {
  	struct task_struct *tsk = current;

  	struct irq_desc *desc;

  
  	if (!tsk->irqaction)
  		return;
  
  	printk(KERN_ERR
  	       "exiting task \"%s\" (%d) is an active IRQ thread (irq %d)
  ",
  	       tsk->comm ? tsk->comm : "", tsk->pid, tsk->irqaction->irq);

  	desc = irq_to_desc(tsk->irqaction->irq);
  
  	/*
  	 * Prevent a stale desc->threads_oneshot. Must be called
  	 * before setting the IRQTF_DIED flag.
  	 */
  	irq_finalize_oneshot(desc, tsk->irqaction, true);

  	/*
  	 * Set the THREAD DIED flag to prevent further wakeups of the
  	 * soon to be gone threaded handler.
  	 */
  	set_bit(IRQTF_DIED, &tsk->irqaction->flags);
  }

  static void irq_setup_forced_threading(struct irqaction *new)
  {
  	if (!force_irqthreads)
  		return;
  	if (new->flags & (IRQF_NO_THREAD | IRQF_PERCPU | IRQF_ONESHOT))
  		return;
  
  	new->flags |= IRQF_ONESHOT;
  
  	if (!new->thread_fn) {
  		set_bit(IRQTF_FORCED_THREAD, &new->thread_flags);
  		new->thread_fn = new->handler;
  		new->handler = irq_default_primary_handler;
  	}
  }

  /*
   * Internal function to register an irqaction - typically used to
   * allocate special interrupts that are part of the architecture.
   */

  static int

  __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)

  {

  	struct irqaction *old, **old_ptr;

  	const char *old_name = NULL;

  	unsigned long flags, thread_mask = 0;

  	int ret, nested, shared = 0;
  	cpumask_var_t mask;

  	if (!desc)

  		return -EINVAL;

  	if (desc->irq_data.chip == &no_irq_chip)

  		return -ENOSYS;

  	if (!try_module_get(desc->owner))
  		return -ENODEV;

  	/*
  	 * Some drivers like serial.c use request_irq() heavily,
  	 * so we have to be careful not to interfere with a
  	 * running system.
  	 */

  	if (new->flags & IRQF_SAMPLE_RANDOM) {

  		/*
  		 * This function might sleep, we want to call it first,
  		 * outside of the atomic block.
  		 * Yes, this might clear the entropy pool if the wrong
  		 * driver is attempted to be loaded, without actually
  		 * installing a new handler, but is this really a problem,
  		 * only the sysadmin is able to do this.
  		 */
  		rand_initialize_irq(irq);
  	}
  
  	/*

  	 * Check whether the interrupt nests into another interrupt
  	 * thread.
  	 */

  	nested = irq_settings_is_nested_thread(desc);

  	if (nested) {

  		if (!new->thread_fn) {
  			ret = -EINVAL;
  			goto out_mput;
  		}

  		/*
  		 * Replace the primary handler which was provided from
  		 * the driver for non nested interrupt handling by the
  		 * dummy function which warns when called.
  		 */
  		new->handler = irq_nested_primary_handler;

  	} else {

  		if (irq_settings_can_thread(desc))
  			irq_setup_forced_threading(new);

  	}

  	/*

  	 * Create a handler thread when a thread function is supplied
  	 * and the interrupt does not nest into another interrupt
  	 * thread.

  	 */

  	if (new->thread_fn && !nested) {

  		struct task_struct *t;
  
  		t = kthread_create(irq_thread, new, "irq/%d-%s", irq,
  				   new->name);

  		if (IS_ERR(t)) {
  			ret = PTR_ERR(t);
  			goto out_mput;
  		}

  		/*
  		 * We keep the reference to the task struct even if
  		 * the thread dies to avoid that the interrupt code
  		 * references an already freed task_struct.
  		 */
  		get_task_struct(t);
  		new->thread = t;

  	}

  	if (!alloc_cpumask_var(&mask, GFP_KERNEL)) {
  		ret = -ENOMEM;
  		goto out_thread;
  	}

  	/*

  	 * The following block of code has to be executed atomically
  	 */

  	raw_spin_lock_irqsave(&desc->lock, flags);

  	old_ptr = &desc->action;
  	old = *old_ptr;

  	if (old) {

  		/*
  		 * Can't share interrupts unless both agree to and are
  		 * the same type (level, edge, polarity). So both flag

  		 * fields must have IRQF_SHARED set and the bits which

  		 * set the trigger type must match. Also all must
  		 * agree on ONESHOT.

  		 */

  		if (!((old->flags & new->flags) & IRQF_SHARED) ||

  		    ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK) ||
  		    ((old->flags ^ new->flags) & IRQF_ONESHOT)) {

  			old_name = old->name;

  			goto mismatch;

  		}

  		/* All handlers must agree on per-cpuness */

  		if ((old->flags & IRQF_PERCPU) !=
  		    (new->flags & IRQF_PERCPU))

  			goto mismatch;

  
  		/* add new interrupt at end of irq queue */
  		do {

  			thread_mask |= old->thread_mask;

  			old_ptr = &old->next;
  			old = *old_ptr;

  		} while (old);
  		shared = 1;
  	}

  	/*
  	 * Setup the thread mask for this irqaction. Unlikely to have
  	 * 32 resp 64 irqs sharing one line, but who knows.
  	 */
  	if (new->flags & IRQF_ONESHOT && thread_mask == ~0UL) {
  		ret = -EBUSY;
  		goto out_mask;
  	}
  	new->thread_mask = 1 << ffz(thread_mask);

  	if (!shared) {

  		init_waitqueue_head(&desc->wait_for_threads);

  		/* Setup the type (level, edge polarity) if configured: */

  		if (new->flags & IRQF_TRIGGER_MASK) {

  			ret = __irq_set_trigger(desc, irq,
  					new->flags & IRQF_TRIGGER_MASK);

  			if (ret)

  				goto out_mask;

  		}

  		desc->istate &= ~(IRQS_AUTODETECT | IRQS_SPURIOUS_DISABLED | \

  				  IRQS_ONESHOT | IRQS_WAITING);
  		irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);

  		if (new->flags & IRQF_PERCPU) {
  			irqd_set(&desc->irq_data, IRQD_PER_CPU);
  			irq_settings_set_per_cpu(desc);
  		}

  		if (new->flags & IRQF_ONESHOT)

  			desc->istate |= IRQS_ONESHOT;

  		if (irq_settings_can_autoenable(desc))

  			irq_startup(desc);
  		else

  			/* Undo nested disables: */
  			desc->depth = 1;

  		/* Exclude IRQ from balancing if requested */

  		if (new->flags & IRQF_NOBALANCING) {
  			irq_settings_set_no_balancing(desc);
  			irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
  		}

  		/* Set default affinity mask once everything is setup */

  		setup_affinity(irq, desc, mask);

  	} else if (new->flags & IRQF_TRIGGER_MASK) {
  		unsigned int nmsk = new->flags & IRQF_TRIGGER_MASK;
  		unsigned int omsk = irq_settings_get_trigger_mask(desc);
  
  		if (nmsk != omsk)
  			/* hope the handler works with current  trigger mode */
  			pr_warning("IRQ %d uses trigger mode %u; requested %u
  ",
  				   irq, nmsk, omsk);

  	}

  	new->irq = irq;

  	*old_ptr = new;

  	/* Reset broken irq detection when installing new handler */
  	desc->irq_count = 0;
  	desc->irqs_unhandled = 0;

  
  	/*
  	 * Check whether we disabled the irq via the spurious handler
  	 * before. Reenable it and give it another chance.
  	 */

  	if (shared && (desc->istate & IRQS_SPURIOUS_DISABLED)) {
  		desc->istate &= ~IRQS_SPURIOUS_DISABLED;

  		__enable_irq(desc, irq, false);

  	}

  	raw_spin_unlock_irqrestore(&desc->lock, flags);

  	/*
  	 * Strictly no need to wake it up, but hung_task complains
  	 * when no hard interrupt wakes the thread up.
  	 */
  	if (new->thread)
  		wake_up_process(new->thread);

  	register_irq_proc(irq, desc);

  	new->dir = NULL;
  	register_handler_proc(irq, new);

  	free_cpumask_var(mask);

  
  	return 0;

  
  mismatch:

  #ifdef CONFIG_DEBUG_SHIRQ

  	if (!(new->flags & IRQF_PROBE_SHARED)) {

  		printk(KERN_ERR "IRQ handler type mismatch for IRQ %d
  ", irq);

  		if (old_name)
  			printk(KERN_ERR "current handler: %s
  ", old_name);

  		dump_stack();
  	}

  #endif

  	ret = -EBUSY;

  out_mask:

  	raw_spin_unlock_irqrestore(&desc->lock, flags);

  	free_cpumask_var(mask);

  out_thread:

  	if (new->thread) {
  		struct task_struct *t = new->thread;
  
  		new->thread = NULL;
  		if (likely(!test_bit(IRQTF_DIED, &new->thread_flags)))
  			kthread_stop(t);
  		put_task_struct(t);
  	}

  out_mput:
  	module_put(desc->owner);

  	return ret;

  }
  
  /**

   *	setup_irq - setup an interrupt
   *	@irq: Interrupt line to setup
   *	@act: irqaction for the interrupt
   *
   * Used to statically setup interrupts in the early boot process.
   */
  int setup_irq(unsigned int irq, struct irqaction *act)
  {

  	int retval;

  	struct irq_desc *desc = irq_to_desc(irq);

  	if (WARN_ON(irq_settings_is_per_cpu_devid(desc)))
  		return -EINVAL;

  	chip_bus_lock(desc);
  	retval = __setup_irq(irq, desc, act);
  	chip_bus_sync_unlock(desc);
  
  	return retval;

  }

  EXPORT_SYMBOL_GPL(setup_irq);

  /*

   * Internal function to unregister an irqaction - used to free
   * regular and special interrupts that are part of the architecture.

   */

  static struct irqaction *__free_irq(unsigned int irq, void *dev_id)

  {

  	struct irq_desc *desc = irq_to_desc(irq);

  	struct irqaction *action, **action_ptr;

  	unsigned long flags;

  	WARN(in_interrupt(), "Trying to free IRQ %d from IRQ context!
  ", irq);

  	if (!desc)

  		return NULL;

  	raw_spin_lock_irqsave(&desc->lock, flags);

  
  	/*
  	 * There can be multiple actions per IRQ descriptor, find the right
  	 * one based on the dev_id:
  	 */

  	action_ptr = &desc->action;

  	for (;;) {

  		action = *action_ptr;

  		if (!action) {
  			WARN(1, "Trying to free already-free IRQ %d
  ", irq);

  			raw_spin_unlock_irqrestore(&desc->lock, flags);

  			return NULL;

  		}

  		if (action->dev_id == dev_id)
  			break;

  		action_ptr = &action->next;

  	}

  	/* Found it - now remove it from the list of entries: */

  	*action_ptr = action->next;

  
  	/* Currently used only by UML, might disappear one day: */

  #ifdef CONFIG_IRQ_RELEASE_METHOD

  	if (desc->irq_data.chip->release)
  		desc->irq_data.chip->release(irq, dev_id);

  #endif

  	/* If this was the last handler, shut down the IRQ line: */

  	if (!desc->action)
  		irq_shutdown(desc);

  #ifdef CONFIG_SMP
  	/* make sure affinity_hint is cleaned up */
  	if (WARN_ON_ONCE(desc->affinity_hint))
  		desc->affinity_hint = NULL;
  #endif

  	raw_spin_unlock_irqrestore(&desc->lock, flags);

  
  	unregister_handler_proc(irq, action);
  
  	/* Make sure it's not being used on another CPU: */
  	synchronize_irq(irq);

  #ifdef CONFIG_DEBUG_SHIRQ

  	/*
  	 * It's a shared IRQ -- the driver ought to be prepared for an IRQ
  	 * event to happen even now it's being freed, so let's make sure that
  	 * is so by doing an extra call to the handler ....
  	 *
  	 * ( We do this after actually deregistering it, to make sure that a
  	 *   'real' IRQ doesn't run in * parallel with our fake. )
  	 */
  	if (action->flags & IRQF_SHARED) {
  		local_irq_save(flags);
  		action->handler(irq, dev_id);
  		local_irq_restore(flags);

  	}

  #endif

  
  	if (action->thread) {
  		if (!test_bit(IRQTF_DIED, &action->thread_flags))
  			kthread_stop(action->thread);
  		put_task_struct(action->thread);
  	}

  	module_put(desc->owner);

  	return action;
  }
  
  /**

   *	remove_irq - free an interrupt
   *	@irq: Interrupt line to free
   *	@act: irqaction for the interrupt
   *
   * Used to remove interrupts statically setup by the early boot process.
   */
  void remove_irq(unsigned int irq, struct irqaction *act)
  {

  	struct irq_desc *desc = irq_to_desc(irq);
  
  	if (desc && !WARN_ON(irq_settings_is_per_cpu_devid(desc)))
  	    __free_irq(irq, act->dev_id);

  }

  EXPORT_SYMBOL_GPL(remove_irq);

  
  /**

   *	free_irq - free an interrupt allocated with request_irq
   *	@irq: Interrupt line to free
   *	@dev_id: Device identity to free
   *
   *	Remove an interrupt handler. The handler is removed and if the
   *	interrupt line is no longer in use by any driver it is disabled.
   *	On a shared IRQ the caller must ensure the interrupt is disabled
   *	on the card it drives before calling this function. The function
   *	does not return until any executing interrupts for this IRQ
   *	have completed.
   *
   *	This function must not be called from interrupt context.
   */
  void free_irq(unsigned int irq, void *dev_id)
  {

  	struct irq_desc *desc = irq_to_desc(irq);

  	if (!desc || WARN_ON(irq_settings_is_per_cpu_devid(desc)))

  		return;

  #ifdef CONFIG_SMP
  	if (WARN_ON(desc->affinity_notify))
  		desc->affinity_notify = NULL;
  #endif

  	chip_bus_lock(desc);

  	kfree(__free_irq(irq, dev_id));

  	chip_bus_sync_unlock(desc);

  }

  EXPORT_SYMBOL(free_irq);
  
  /**

   *	request_threaded_irq - allocate an interrupt line

   *	@irq: Interrupt line to allocate

   *	@handler: Function to be called when the IRQ occurs.
   *		  Primary handler for threaded interrupts

   *		  If NULL and thread_fn != NULL the default
   *		  primary handler is installed

   *	@thread_fn: Function called from the irq handler thread
   *		    If NULL, no irq thread is created

   *	@irqflags: Interrupt type flags
   *	@devname: An ascii name for the claiming device
   *	@dev_id: A cookie passed back to the handler function
   *
   *	This call allocates interrupt resources and enables the
   *	interrupt line and IRQ handling. From the point this
   *	call is made your handler function may be invoked. Since
   *	your handler function must clear any interrupt the board
   *	raises, you must take care both to initialise your hardware
   *	and to set up the interrupt handler in the right order.
   *

   *	If you want to set up a threaded irq handler for your device

   *	then you need to supply @handler and @thread_fn. @handler is

   *	still called in hard interrupt context and has to check
   *	whether the interrupt originates from the device. If yes it
   *	needs to disable the interrupt on the device and return

   *	IRQ_WAKE_THREAD which will wake up the handler thread and run

   *	@thread_fn. This split handler design is necessary to support
   *	shared interrupts.
   *

   *	Dev_id must be globally unique. Normally the address of the
   *	device data structure is used as the cookie. Since the handler
   *	receives this value it makes sense to use it.
   *
   *	If your interrupt is shared you must pass a non NULL dev_id
   *	as this is required when freeing the interrupt.
   *
   *	Flags:
   *

   *	IRQF_SHARED		Interrupt is shared

   *	IRQF_SAMPLE_RANDOM	The interrupt can be used for entropy

   *	IRQF_TRIGGER_*		Specify active edge(s) or level

   *
   */

  int request_threaded_irq(unsigned int irq, irq_handler_t handler,
  			 irq_handler_t thread_fn, unsigned long irqflags,
  			 const char *devname, void *dev_id)

  {

  	struct irqaction *action;

  	struct irq_desc *desc;

  	int retval;

  	/*

  	 * Sanity-check: shared interrupts must pass in a real dev-ID,
  	 * otherwise we'll have trouble later trying to figure out
  	 * which interrupt is which (messes up the interrupt freeing
  	 * logic etc).
  	 */

  	if ((irqflags & IRQF_SHARED) && !dev_id)

  		return -EINVAL;

  	desc = irq_to_desc(irq);

  	if (!desc)

  		return -EINVAL;

  	if (!irq_settings_can_request(desc) ||
  	    WARN_ON(irq_settings_is_per_cpu_devid(desc)))

  		return -EINVAL;

  
  	if (!handler) {
  		if (!thread_fn)
  			return -EINVAL;
  		handler = irq_default_primary_handler;
  	}

  	action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);

  	if (!action)
  		return -ENOMEM;
  
  	action->handler = handler;

  	action->thread_fn = thread_fn;

  	action->flags = irqflags;

  	action->name = devname;

  	action->dev_id = dev_id;

  	chip_bus_lock(desc);

  	retval = __setup_irq(irq, desc, action);

  	chip_bus_sync_unlock(desc);

  	if (retval)
  		kfree(action);

  #ifdef CONFIG_DEBUG_SHIRQ_FIXME

  	if (!retval && (irqflags & IRQF_SHARED)) {

  		/*
  		 * It's a shared IRQ -- the driver ought to be prepared for it
  		 * to happen immediately, so let's make sure....

  		 * We disable the irq to make sure that a 'real' IRQ doesn't
  		 * run in parallel with our fake.

  		 */

  		unsigned long flags;

  		disable_irq(irq);

  		local_irq_save(flags);

  		handler(irq, dev_id);

  		local_irq_restore(flags);

  		enable_irq(irq);

  	}
  #endif

  	return retval;
  }

  EXPORT_SYMBOL(request_threaded_irq);

  
  /**
   *	request_any_context_irq - allocate an interrupt line
   *	@irq: Interrupt line to allocate
   *	@handler: Function to be called when the IRQ occurs.
   *		  Threaded handler for threaded interrupts.
   *	@flags: Interrupt type flags
   *	@name: An ascii name for the claiming device
   *	@dev_id: A cookie passed back to the handler function
   *
   *	This call allocates interrupt resources and enables the
   *	interrupt line and IRQ handling. It selects either a
   *	hardirq or threaded handling method depending on the
   *	context.
   *
   *	On failure, it returns a negative value. On success,
   *	it returns either IRQC_IS_HARDIRQ or IRQC_IS_NESTED.
   */
  int request_any_context_irq(unsigned int irq, irq_handler_t handler,
  			    unsigned long flags, const char *name, void *dev_id)
  {
  	struct irq_desc *desc = irq_to_desc(irq);
  	int ret;
  
  	if (!desc)
  		return -EINVAL;

  	if (irq_settings_is_nested_thread(desc)) {

  		ret = request_threaded_irq(irq, NULL, handler,
  					   flags, name, dev_id);
  		return !ret ? IRQC_IS_NESTED : ret;
  	}
  
  	ret = request_irq(irq, handler, flags, name, dev_id);
  	return !ret ? IRQC_IS_HARDIRQ : ret;
  }
  EXPORT_SYMBOL_GPL(request_any_context_irq);

  void enable_percpu_irq(unsigned int irq, unsigned int type)

  {
  	unsigned int cpu = smp_processor_id();
  	unsigned long flags;
  	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, IRQ_GET_DESC_CHECK_PERCPU);
  
  	if (!desc)
  		return;

  	type &= IRQ_TYPE_SENSE_MASK;
  	if (type != IRQ_TYPE_NONE) {
  		int ret;
  
  		ret = __irq_set_trigger(desc, irq, type);
  
  		if (ret) {

  			WARN(1, "failed to set type for IRQ%d
  ", irq);

  			goto out;
  		}
  	}

  	irq_percpu_enable(desc, cpu);

  out:

  	irq_put_desc_unlock(desc, flags);
  }
  
  void disable_percpu_irq(unsigned int irq)
  {
  	unsigned int cpu = smp_processor_id();
  	unsigned long flags;
  	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, IRQ_GET_DESC_CHECK_PERCPU);
  
  	if (!desc)
  		return;
  
  	irq_percpu_disable(desc, cpu);
  	irq_put_desc_unlock(desc, flags);
  }
  
  /*
   * Internal function to unregister a percpu irqaction.
   */
  static struct irqaction *__free_percpu_irq(unsigned int irq, void __percpu *dev_id)
  {
  	struct irq_desc *desc = irq_to_desc(irq);
  	struct irqaction *action;
  	unsigned long flags;
  
  	WARN(in_interrupt(), "Trying to free IRQ %d from IRQ context!
  ", irq);
  
  	if (!desc)
  		return NULL;
  
  	raw_spin_lock_irqsave(&desc->lock, flags);
  
  	action = desc->action;
  	if (!action || action->percpu_dev_id != dev_id) {
  		WARN(1, "Trying to free already-free IRQ %d
  ", irq);
  		goto bad;
  	}
  
  	if (!cpumask_empty(desc->percpu_enabled)) {
  		WARN(1, "percpu IRQ %d still enabled on CPU%d!
  ",
  		     irq, cpumask_first(desc->percpu_enabled));
  		goto bad;
  	}
  
  	/* Found it - now remove it from the list of entries: */
  	desc->action = NULL;
  
  	raw_spin_unlock_irqrestore(&desc->lock, flags);
  
  	unregister_handler_proc(irq, action);
  
  	module_put(desc->owner);
  	return action;
  
  bad:
  	raw_spin_unlock_irqrestore(&desc->lock, flags);
  	return NULL;
  }
  
  /**
   *	remove_percpu_irq - free a per-cpu interrupt
   *	@irq: Interrupt line to free
   *	@act: irqaction for the interrupt
   *
   * Used to remove interrupts statically setup by the early boot process.
   */
  void remove_percpu_irq(unsigned int irq, struct irqaction *act)
  {
  	struct irq_desc *desc = irq_to_desc(irq);
  
  	if (desc && irq_settings_is_per_cpu_devid(desc))
  	    __free_percpu_irq(irq, act->percpu_dev_id);
  }
  
  /**
   *	free_percpu_irq - free an interrupt allocated with request_percpu_irq
   *	@irq: Interrupt line to free
   *	@dev_id: Device identity to free
   *
   *	Remove a percpu interrupt handler. The handler is removed, but
   *	the interrupt line is not disabled. This must be done on each
   *	CPU before calling this function. The function does not return
   *	until any executing interrupts for this IRQ have completed.
   *
   *	This function must not be called from interrupt context.
   */
  void free_percpu_irq(unsigned int irq, void __percpu *dev_id)
  {
  	struct irq_desc *desc = irq_to_desc(irq);
  
  	if (!desc || !irq_settings_is_per_cpu_devid(desc))
  		return;
  
  	chip_bus_lock(desc);
  	kfree(__free_percpu_irq(irq, dev_id));
  	chip_bus_sync_unlock(desc);
  }
  
  /**
   *	setup_percpu_irq - setup a per-cpu interrupt
   *	@irq: Interrupt line to setup
   *	@act: irqaction for the interrupt
   *
   * Used to statically setup per-cpu interrupts in the early boot process.
   */
  int setup_percpu_irq(unsigned int irq, struct irqaction *act)
  {
  	struct irq_desc *desc = irq_to_desc(irq);
  	int retval;
  
  	if (!desc || !irq_settings_is_per_cpu_devid(desc))
  		return -EINVAL;
  	chip_bus_lock(desc);
  	retval = __setup_irq(irq, desc, act);
  	chip_bus_sync_unlock(desc);
  
  	return retval;
  }
  
  /**
   *	request_percpu_irq - allocate a percpu interrupt line
   *	@irq: Interrupt line to allocate
   *	@handler: Function to be called when the IRQ occurs.
   *	@devname: An ascii name for the claiming device
   *	@dev_id: A percpu cookie passed back to the handler function
   *
   *	This call allocates interrupt resources, but doesn't
   *	automatically enable the interrupt. It has to be done on each
   *	CPU using enable_percpu_irq().
   *
   *	Dev_id must be globally unique. It is a per-cpu variable, and
   *	the handler gets called with the interrupted CPU's instance of
   *	that variable.
   */
  int request_percpu_irq(unsigned int irq, irq_handler_t handler,
  		       const char *devname, void __percpu *dev_id)
  {
  	struct irqaction *action;
  	struct irq_desc *desc;
  	int retval;
  
  	if (!dev_id)
  		return -EINVAL;
  
  	desc = irq_to_desc(irq);
  	if (!desc || !irq_settings_can_request(desc) ||
  	    !irq_settings_is_per_cpu_devid(desc))
  		return -EINVAL;
  
  	action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
  	if (!action)
  		return -ENOMEM;
  
  	action->handler = handler;

  	action->flags = IRQF_PERCPU | IRQF_NO_SUSPEND;

  	action->name = devname;
  	action->percpu_dev_id = dev_id;
  
  	chip_bus_lock(desc);
  	retval = __setup_irq(irq, desc, action);
  	chip_bus_sync_unlock(desc);
  
  	if (retval)
  		kfree(action);
  
  	return retval;
  }