kernel/irq/spurious.c - arm/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * linux/kernel/irq/spurious.c
  *
  * Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
  *
  * This file contains spurious interrupt handling.
  */

 #include <linux/jiffies.h>
 #include <linux/irq.h>
 #include <linux/module.h>
 #include <linux/kallsyms.h>
 #include <linux/interrupt.h>
 #include <linux/moduleparam.h>
 #include <linux/timer.h>

 #include "internals.h"

 static int irqfixup __read_mostly;

 #define POLL_SPURIOUS_IRQ_INTERVAL (HZ/10)
 static void poll_spurious_irqs(unsigned long dummy);
 static DEFINE_TIMER(poll_spurious_irq_timer, poll_spurious_irqs, 0, 0);
 static int irq_poll_cpu;
 static atomic_t irq_poll_active;

 /*
  * We wait here for a poller to finish.
  *
  * If the poll runs on this CPU, then we yell loudly and return
  * false. That will leave the interrupt line disabled in the worst
  * case, but it should never happen.
  *
  * We wait until the poller is done and then recheck disabled and
  * action (about to be disabled). Only if it's still active, we return
  * true and let the handler run.
  */
 bool irq_wait_for_poll(struct irq_desc *desc)
 {
 	if (WARN_ONCE(irq_poll_cpu == smp_processor_id(),
 		      "irq poll in progress on cpu %d for irq %d\n",
 		      smp_processor_id(), desc->irq_data.irq))
 		return false;

 #ifdef CONFIG_SMP
 	do {
 		raw_spin_unlock(&desc->lock);
 		while (irqd_irq_inprogress(&desc->irq_data))
 			cpu_relax();
 		raw_spin_lock(&desc->lock);
 	} while (irqd_irq_inprogress(&desc->irq_data));
 	/* Might have been disabled in meantime */
 	return !irqd_irq_disabled(&desc->irq_data) && desc->action;
 #else
 	return false;
 #endif
 }


 /*
  * Recovery handler for misrouted interrupts.
  */
 static int try_one_irq(struct irq_desc *desc, bool force)
 {
 	irqreturn_t ret = IRQ_NONE;
 	struct irqaction *action;

 	raw_spin_lock(&desc->lock);

 	/*
 	 * PER_CPU, nested thread interrupts and interrupts explicitely
 	 * marked polled are excluded from polling.
 	 */
 	if (irq_settings_is_per_cpu(desc) ||
 	    irq_settings_is_nested_thread(desc) ||
 	    irq_settings_is_polled(desc))
 		goto out;

 	/*
 	 * Do not poll disabled interrupts unless the spurious
 	 * disabled poller asks explicitely.
 	 */
 	if (irqd_irq_disabled(&desc->irq_data) && !force)
 		goto out;

 	/*
 	 * All handlers must agree on IRQF_SHARED, so we test just the
 	 * first.
 	 */
 	action = desc->action;
 	if (!action || !(action->flags & IRQF_SHARED) ||
 	    (action->flags & __IRQF_TIMER))
 		goto out;

 	/* Already running on another processor */
 	if (irqd_irq_inprogress(&desc->irq_data)) {
 		/*
 		 * Already running: If it is shared get the other
 		 * CPU to go looking for our mystery interrupt too
 		 */
 		desc->istate |= IRQS_PENDING;
 		goto out;
 	}

 	/* Mark it poll in progress */
 	desc->istate |= IRQS_POLL_INPROGRESS;
 	do {
 		if (handle_irq_event(desc) == IRQ_HANDLED)
 			ret = IRQ_HANDLED;
 		/* Make sure that there is still a valid action */
 		action = desc->action;
 	} while ((desc->istate & IRQS_PENDING) && action);
 	desc->istate &= ~IRQS_POLL_INPROGRESS;
 out:
 	raw_spin_unlock(&desc->lock);
 	return ret == IRQ_HANDLED;
 }

 static int misrouted_irq(int irq)
 {
 	struct irq_desc *desc;
 	int i, ok = 0;

 	if (atomic_inc_return(&irq_poll_active) != 1)
 		goto out;

 	irq_poll_cpu = smp_processor_id();

 	for_each_irq_desc(i, desc) {
 		if (!i)
 			 continue;

 		if (i == irq)	/* Already tried */
 			continue;

 		if (try_one_irq(desc, false))
 			ok = 1;
 	}
 out:
 	atomic_dec(&irq_poll_active);
 	/* So the caller can adjust the irq error counts */
 	return ok;
 }

 static void poll_spurious_irqs(unsigned long dummy)
 {
 	struct irq_desc *desc;
 	int i;

 	if (atomic_inc_return(&irq_poll_active) != 1)
 		goto out;
 	irq_poll_cpu = smp_processor_id();

 	for_each_irq_desc(i, desc) {
 		unsigned int state;

 		if (!i)
 			 continue;

 		/* Racy but it doesn't matter */
 		state = desc->istate;
 		barrier();
 		if (!(state & IRQS_SPURIOUS_DISABLED))
 			continue;

 		local_irq_disable();
 		try_one_irq(desc, true);
 		local_irq_enable();
 	}
 out:
 	atomic_dec(&irq_poll_active);
 	mod_timer(&poll_spurious_irq_timer,
 		  jiffies + POLL_SPURIOUS_IRQ_INTERVAL);
 }

 static inline int bad_action_ret(irqreturn_t action_ret)
 {
 	unsigned int r = action_ret;

 	if (likely(r <= (IRQ_HANDLED | IRQ_WAKE_THREAD)))
 		return 0;
 	return 1;
 }

 /*
  * If 99,900 of the previous 100,000 interrupts have not been handled
  * then assume that the IRQ is stuck in some manner. Drop a diagnostic
  * and try to turn the IRQ off.
  *
  * (The other 100-of-100,000 interrupts may have been a correctly
  *  functioning device sharing an IRQ with the failing one)
  */
 static void __report_bad_irq(struct irq_desc *desc, irqreturn_t action_ret)
 {
 	unsigned int irq = irq_desc_get_irq(desc);
 	struct irqaction *action;
 	unsigned long flags;

 	if (bad_action_ret(action_ret)) {
 		printk(KERN_ERR "irq event %d: bogus return value %x\n",
 				irq, action_ret);
 	} else {
 		printk(KERN_ERR "irq %d: nobody cared (try booting with "
 				"the \"irqpoll\" option)\n", irq);
 	}
 	dump_stack();
 	printk(KERN_ERR "handlers:\n");

 	/*
 	 * We need to take desc->lock here. note_interrupt() is called
 	 * w/o desc->lock held, but IRQ_PROGRESS set. We might race
 	 * with something else removing an action. It's ok to take
 	 * desc->lock here. See synchronize_irq().
 	 */
 	raw_spin_lock_irqsave(&desc->lock, flags);
 	for_each_action_of_desc(desc, action) {
 		printk(KERN_ERR "[<%p>] %pf", action->handler, action->handler);
 		if (action->thread_fn)
 			printk(KERN_CONT " threaded [<%p>] %pf",
 					action->thread_fn, action->thread_fn);
 		printk(KERN_CONT "\n");
 	}
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 }

 static void report_bad_irq(struct irq_desc *desc, irqreturn_t action_ret)
 {
 	static int count = 100;

 	if (count > 0) {
 		count--;
 		__report_bad_irq(desc, action_ret);
 	}
 }

 static inline int
 try_misrouted_irq(unsigned int irq, struct irq_desc *desc,
 		  irqreturn_t action_ret)
 {
 	struct irqaction *action;

 	if (!irqfixup)
 		return 0;

 	/* We didn't actually handle the IRQ - see if it was misrouted? */
 	if (action_ret == IRQ_NONE)
 		return 1;

 	/*
 	 * But for 'irqfixup == 2' we also do it for handled interrupts if
 	 * they are marked as IRQF_IRQPOLL (or for irq zero, which is the
 	 * traditional PC timer interrupt.. Legacy)
 	 */
 	if (irqfixup < 2)
 		return 0;

 	if (!irq)
 		return 1;

 	/*
 	 * Since we don't get the descriptor lock, "action" can
 	 * change under us.  We don't really care, but we don't
 	 * want to follow a NULL pointer. So tell the compiler to
 	 * just load it once by using a barrier.
 	 */
 	action = desc->action;
 	barrier();
 	return action && (action->flags & IRQF_IRQPOLL);
 }

 #define SPURIOUS_DEFERRED	0x80000000

 void note_interrupt(struct irq_desc *desc, irqreturn_t action_ret)
 {
 	unsigned int irq;

 	if (desc->istate & IRQS_POLL_INPROGRESS ||
 	    irq_settings_is_polled(desc))
 		return;

 	if (bad_action_ret(action_ret)) {
 		report_bad_irq(desc, action_ret);
 		return;
 	}

 	/*
 	 * We cannot call note_interrupt from the threaded handler
 	 * because we need to look at the compound of all handlers
 	 * (primary and threaded). Aside of that in the threaded
 	 * shared case we have no serialization against an incoming
 	 * hardware interrupt while we are dealing with a threaded
 	 * result.
 	 *
 	 * So in case a thread is woken, we just note the fact and
 	 * defer the analysis to the next hardware interrupt.
 	 *
 	 * The threaded handlers store whether they sucessfully
 	 * handled an interrupt and we check whether that number
 	 * changed versus the last invocation.
 	 *
 	 * We could handle all interrupts with the delayed by one
 	 * mechanism, but for the non forced threaded case we'd just
 	 * add pointless overhead to the straight hardirq interrupts
 	 * for the sake of a few lines less code.
 	 */
 	if (action_ret & IRQ_WAKE_THREAD) {
 		/*
 		 * There is a thread woken. Check whether one of the
 		 * shared primary handlers returned IRQ_HANDLED. If
 		 * not we defer the spurious detection to the next
 		 * interrupt.
 		 */
 		if (action_ret == IRQ_WAKE_THREAD) {
 			int handled;
 			/*
 			 * We use bit 31 of thread_handled_last to
 			 * denote the deferred spurious detection
 			 * active. No locking necessary as
 			 * thread_handled_last is only accessed here
 			 * and we have the guarantee that hard
 			 * interrupts are not reentrant.
 			 */
 			if (!(desc->threads_handled_last & SPURIOUS_DEFERRED)) {
 				desc->threads_handled_last |= SPURIOUS_DEFERRED;
 				return;
 			}
 			/*
 			 * Check whether one of the threaded handlers
 			 * returned IRQ_HANDLED since the last
 			 * interrupt happened.
 			 *
 			 * For simplicity we just set bit 31, as it is
 			 * set in threads_handled_last as well. So we
 			 * avoid extra masking. And we really do not
 			 * care about the high bits of the handled
 			 * count. We just care about the count being
 			 * different than the one we saw before.
 			 */
 			handled = atomic_read(&desc->threads_handled);
 			handled |= SPURIOUS_DEFERRED;
 			if (handled != desc->threads_handled_last) {
 				action_ret = IRQ_HANDLED;
 				/*
 				 * Note: We keep the SPURIOUS_DEFERRED
 				 * bit set. We are handling the
 				 * previous invocation right now.
 				 * Keep it for the current one, so the
 				 * next hardware interrupt will
 				 * account for it.
 				 */
 				desc->threads_handled_last = handled;
 			} else {
 				/*
 				 * None of the threaded handlers felt
 				 * responsible for the last interrupt
 				 *
 				 * We keep the SPURIOUS_DEFERRED bit
 				 * set in threads_handled_last as we
 				 * need to account for the current
 				 * interrupt as well.
 				 */
 				action_ret = IRQ_NONE;
 			}
 		} else {
 			/*
 			 * One of the primary handlers returned
 			 * IRQ_HANDLED. So we don't care about the
 			 * threaded handlers on the same line. Clear
 			 * the deferred detection bit.
 			 *
 			 * In theory we could/should check whether the
 			 * deferred bit is set and take the result of
 			 * the previous run into account here as
 			 * well. But it's really not worth the
 			 * trouble. If every other interrupt is
 			 * handled we never trigger the spurious
 			 * detector. And if this is just the one out
 			 * of 100k unhandled ones which is handled
 			 * then we merily delay the spurious detection
 			 * by one hard interrupt. Not a real problem.
 			 */
 			desc->threads_handled_last &= ~SPURIOUS_DEFERRED;
 		}
 	}

 	if (unlikely(action_ret == IRQ_NONE)) {
 		/*
 		 * If we are seeing only the odd spurious IRQ caused by
 		 * bus asynchronicity then don't eventually trigger an error,
 		 * otherwise the counter becomes a doomsday timer for otherwise
 		 * working systems
 		 */
 		if (time_after(jiffies, desc->last_unhandled + HZ/10))
 			desc->irqs_unhandled = 1;
 		else
 			desc->irqs_unhandled++;
 		desc->last_unhandled = jiffies;
 	}

 	irq = irq_desc_get_irq(desc);
 	if (unlikely(try_misrouted_irq(irq, desc, action_ret))) {
 		int ok = misrouted_irq(irq);
 		if (action_ret == IRQ_NONE)
 			desc->irqs_unhandled -= ok;
 	}

 	desc->irq_count++;
 	if (likely(desc->irq_count < 100000))
 		return;

 	desc->irq_count = 0;
 	if (unlikely(desc->irqs_unhandled > 99900)) {
 		/*
 		 * The interrupt is stuck
 		 */
 		__report_bad_irq(desc, action_ret);
 		/*
 		 * Now kill the IRQ
 		 */
 		printk(KERN_EMERG "Disabling IRQ #%d\n", irq);
 		desc->istate |= IRQS_SPURIOUS_DISABLED;
 		desc->depth++;
 		irq_disable(desc);

 		mod_timer(&poll_spurious_irq_timer,
 			  jiffies + POLL_SPURIOUS_IRQ_INTERVAL);
 	}
 	desc->irqs_unhandled = 0;
 }

 bool noirqdebug __read_mostly;

 int noirqdebug_setup(char *str)
 {
 	noirqdebug = 1;
 	printk(KERN_INFO "IRQ lockup detection disabled\n");

 	return 1;
 }

 __setup("noirqdebug", noirqdebug_setup);
 module_param(noirqdebug, bool, 0644);
 MODULE_PARM_DESC(noirqdebug, "Disable irq lockup detection when true");

 static int __init irqfixup_setup(char *str)
 {
 	irqfixup = 1;
 	printk(KERN_WARNING "Misrouted IRQ fixup support enabled.\n");
 	printk(KERN_WARNING "This may impact system performance.\n");

 	return 1;
 }

 __setup("irqfixup", irqfixup_setup);
 module_param(irqfixup, int, 0644);

 static int __init irqpoll_setup(char *str)
 {
 	irqfixup = 2;
 	printk(KERN_WARNING "Misrouted IRQ fixup and polling support "
 				"enabled\n");
 	printk(KERN_WARNING "This may significantly impact system "
 				"performance\n");
 	return 1;
 }

 __setup("irqpoll", irqpoll_setup);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/kernel/irq/spurious.c
	*
	* Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
	*
	* This file contains spurious interrupt handling.
	*/

	#include <linux/jiffies.h>
	#include <linux/irq.h>
	#include <linux/module.h>
	#include <linux/kallsyms.h>
	#include <linux/interrupt.h>
	#include <linux/moduleparam.h>
	#include <linux/timer.h>

	#include "internals.h"

	static int irqfixup __read_mostly;

	#define POLL_SPURIOUS_IRQ_INTERVAL (HZ/10)
	static void poll_spurious_irqs(unsigned long dummy);
	static DEFINE_TIMER(poll_spurious_irq_timer, poll_spurious_irqs, 0, 0);
	static int irq_poll_cpu;
	static atomic_t irq_poll_active;

	/*
	* We wait here for a poller to finish.
	*
	* If the poll runs on this CPU, then we yell loudly and return
	* false. That will leave the interrupt line disabled in the worst
	* case, but it should never happen.
	*
	* We wait until the poller is done and then recheck disabled and
	* action (about to be disabled). Only if it's still active, we return
	* true and let the handler run.
	*/
	bool irq_wait_for_poll(struct irq_desc *desc)
	{
	if (WARN_ONCE(irq_poll_cpu == smp_processor_id(),
	"irq poll in progress on cpu %d for irq %d\n",
	smp_processor_id(), desc->irq_data.irq))
	return false;

	#ifdef CONFIG_SMP
	do {
	raw_spin_unlock(&desc->lock);
	while (irqd_irq_inprogress(&desc->irq_data))
	cpu_relax();
	raw_spin_lock(&desc->lock);
	} while (irqd_irq_inprogress(&desc->irq_data));
	/* Might have been disabled in meantime */
	return !irqd_irq_disabled(&desc->irq_data) && desc->action;
	#else
	return false;
	#endif
	}


	/*
	* Recovery handler for misrouted interrupts.
	*/
	static int try_one_irq(struct irq_desc *desc, bool force)
	{
	irqreturn_t ret = IRQ_NONE;
	struct irqaction *action;

	raw_spin_lock(&desc->lock);

	/*
	* PER_CPU, nested thread interrupts and interrupts explicitely
	* marked polled are excluded from polling.
	*/
	if (irq_settings_is_per_cpu(desc) \|\|
	irq_settings_is_nested_thread(desc) \|\|
	irq_settings_is_polled(desc))
	goto out;

	/*
	* Do not poll disabled interrupts unless the spurious
	* disabled poller asks explicitely.
	*/
	if (irqd_irq_disabled(&desc->irq_data) && !force)
	goto out;

	/*
	* All handlers must agree on IRQF_SHARED, so we test just the
	* first.
	*/
	action = desc->action;
	if (!action \|\| !(action->flags & IRQF_SHARED) \|\|
	(action->flags & __IRQF_TIMER))
	goto out;

	/* Already running on another processor */
	if (irqd_irq_inprogress(&desc->irq_data)) {
	/*
	* Already running: If it is shared get the other
	* CPU to go looking for our mystery interrupt too
	*/
	desc->istate \|= IRQS_PENDING;
	goto out;
	}

	/* Mark it poll in progress */
	desc->istate \|= IRQS_POLL_INPROGRESS;
	do {
	if (handle_irq_event(desc) == IRQ_HANDLED)
	ret = IRQ_HANDLED;
	/* Make sure that there is still a valid action */
	action = desc->action;
	} while ((desc->istate & IRQS_PENDING) && action);
	desc->istate &= ~IRQS_POLL_INPROGRESS;
	out:
	raw_spin_unlock(&desc->lock);
	return ret == IRQ_HANDLED;
	}

	static int misrouted_irq(int irq)
	{
	struct irq_desc *desc;
	int i, ok = 0;

	if (atomic_inc_return(&irq_poll_active) != 1)
	goto out;

	irq_poll_cpu = smp_processor_id();

	for_each_irq_desc(i, desc) {
	if (!i)
	continue;

	if (i == irq) /* Already tried */
	continue;

	if (try_one_irq(desc, false))
	ok = 1;
	}
	out:
	atomic_dec(&irq_poll_active);
	/* So the caller can adjust the irq error counts */
	return ok;
	}

	static void poll_spurious_irqs(unsigned long dummy)
	{
	struct irq_desc *desc;
	int i;

	if (atomic_inc_return(&irq_poll_active) != 1)
	goto out;
	irq_poll_cpu = smp_processor_id();

	for_each_irq_desc(i, desc) {
	unsigned int state;

	if (!i)
	continue;

	/* Racy but it doesn't matter */
	state = desc->istate;
	barrier();
	if (!(state & IRQS_SPURIOUS_DISABLED))
	continue;

	local_irq_disable();
	try_one_irq(desc, true);
	local_irq_enable();
	}
	out:
	atomic_dec(&irq_poll_active);
	mod_timer(&poll_spurious_irq_timer,
	jiffies + POLL_SPURIOUS_IRQ_INTERVAL);
	}

	static inline int bad_action_ret(irqreturn_t action_ret)
	{
	unsigned int r = action_ret;

	if (likely(r <= (IRQ_HANDLED \| IRQ_WAKE_THREAD)))
	return 0;
	return 1;
	}

	/*
	* If 99,900 of the previous 100,000 interrupts have not been handled
	* then assume that the IRQ is stuck in some manner. Drop a diagnostic
	* and try to turn the IRQ off.
	*
	* (The other 100-of-100,000 interrupts may have been a correctly
	* functioning device sharing an IRQ with the failing one)
	*/
	static void __report_bad_irq(struct irq_desc *desc, irqreturn_t action_ret)
	{
	unsigned int irq = irq_desc_get_irq(desc);
	struct irqaction *action;
	unsigned long flags;

	if (bad_action_ret(action_ret)) {
	printk(KERN_ERR "irq event %d: bogus return value %x\n",
	irq, action_ret);
	} else {
	printk(KERN_ERR "irq %d: nobody cared (try booting with "
	"the \"irqpoll\" option)\n", irq);
	}
	dump_stack();
	printk(KERN_ERR "handlers:\n");

	/*
	* We need to take desc->lock here. note_interrupt() is called
	* w/o desc->lock held, but IRQ_PROGRESS set. We might race
	* with something else removing an action. It's ok to take
	* desc->lock here. See synchronize_irq().
	*/
	raw_spin_lock_irqsave(&desc->lock, flags);
	for_each_action_of_desc(desc, action) {
	printk(KERN_ERR "[<%p>] %pf", action->handler, action->handler);
	if (action->thread_fn)
	printk(KERN_CONT " threaded [<%p>] %pf",
	action->thread_fn, action->thread_fn);
	printk(KERN_CONT "\n");
	}
	raw_spin_unlock_irqrestore(&desc->lock, flags);
	}

	static void report_bad_irq(struct irq_desc *desc, irqreturn_t action_ret)
	{
	static int count = 100;

	if (count > 0) {
	count--;
	__report_bad_irq(desc, action_ret);
	}
	}

	static inline int
	try_misrouted_irq(unsigned int irq, struct irq_desc *desc,
	irqreturn_t action_ret)
	{
	struct irqaction *action;

	if (!irqfixup)
	return 0;

	/* We didn't actually handle the IRQ - see if it was misrouted? */
	if (action_ret == IRQ_NONE)
	return 1;

	/*
	* But for 'irqfixup == 2' we also do it for handled interrupts if
	* they are marked as IRQF_IRQPOLL (or for irq zero, which is the
	* traditional PC timer interrupt.. Legacy)
	*/
	if (irqfixup < 2)
	return 0;

	if (!irq)
	return 1;

	/*
	* Since we don't get the descriptor lock, "action" can
	* change under us. We don't really care, but we don't
	* want to follow a NULL pointer. So tell the compiler to
	* just load it once by using a barrier.
	*/
	action = desc->action;
	barrier();
	return action && (action->flags & IRQF_IRQPOLL);
	}

	#define SPURIOUS_DEFERRED 0x80000000

	void note_interrupt(struct irq_desc *desc, irqreturn_t action_ret)
	{
	unsigned int irq;

	if (desc->istate & IRQS_POLL_INPROGRESS \|\|
	irq_settings_is_polled(desc))
	return;

	if (bad_action_ret(action_ret)) {
	report_bad_irq(desc, action_ret);
	return;
	}

	/*
	* We cannot call note_interrupt from the threaded handler
	* because we need to look at the compound of all handlers
	* (primary and threaded). Aside of that in the threaded
	* shared case we have no serialization against an incoming
	* hardware interrupt while we are dealing with a threaded
	* result.
	*
	* So in case a thread is woken, we just note the fact and
	* defer the analysis to the next hardware interrupt.
	*
	* The threaded handlers store whether they sucessfully
	* handled an interrupt and we check whether that number
	* changed versus the last invocation.
	*
	* We could handle all interrupts with the delayed by one
	* mechanism, but for the non forced threaded case we'd just
	* add pointless overhead to the straight hardirq interrupts
	* for the sake of a few lines less code.
	*/
	if (action_ret & IRQ_WAKE_THREAD) {
	/*
	* There is a thread woken. Check whether one of the
	* shared primary handlers returned IRQ_HANDLED. If
	* not we defer the spurious detection to the next
	* interrupt.
	*/
	if (action_ret == IRQ_WAKE_THREAD) {
	int handled;
	/*
	* We use bit 31 of thread_handled_last to
	* denote the deferred spurious detection
	* active. No locking necessary as
	* thread_handled_last is only accessed here
	* and we have the guarantee that hard
	* interrupts are not reentrant.
	*/
	if (!(desc->threads_handled_last & SPURIOUS_DEFERRED)) {
	desc->threads_handled_last \|= SPURIOUS_DEFERRED;
	return;
	}
	/*
	* Check whether one of the threaded handlers
	* returned IRQ_HANDLED since the last
	* interrupt happened.
	*
	* For simplicity we just set bit 31, as it is
	* set in threads_handled_last as well. So we
	* avoid extra masking. And we really do not
	* care about the high bits of the handled
	* count. We just care about the count being
	* different than the one we saw before.
	*/
	handled = atomic_read(&desc->threads_handled);
	handled \|= SPURIOUS_DEFERRED;
	if (handled != desc->threads_handled_last) {
	action_ret = IRQ_HANDLED;
	/*
	* Note: We keep the SPURIOUS_DEFERRED
	* bit set. We are handling the
	* previous invocation right now.
	* Keep it for the current one, so the
	* next hardware interrupt will
	* account for it.
	*/
	desc->threads_handled_last = handled;
	} else {
	/*
	* None of the threaded handlers felt
	* responsible for the last interrupt
	*
	* We keep the SPURIOUS_DEFERRED bit
	* set in threads_handled_last as we
	* need to account for the current
	* interrupt as well.
	*/
	action_ret = IRQ_NONE;
	}
	} else {
	/*
	* One of the primary handlers returned
	* IRQ_HANDLED. So we don't care about the
	* threaded handlers on the same line. Clear
	* the deferred detection bit.
	*
	* In theory we could/should check whether the
	* deferred bit is set and take the result of
	* the previous run into account here as
	* well. But it's really not worth the
	* trouble. If every other interrupt is
	* handled we never trigger the spurious
	* detector. And if this is just the one out
	* of 100k unhandled ones which is handled
	* then we merily delay the spurious detection
	* by one hard interrupt. Not a real problem.
	*/
	desc->threads_handled_last &= ~SPURIOUS_DEFERRED;
	}
	}

	if (unlikely(action_ret == IRQ_NONE)) {
	/*
	* If we are seeing only the odd spurious IRQ caused by
	* bus asynchronicity then don't eventually trigger an error,
	* otherwise the counter becomes a doomsday timer for otherwise
	* working systems
	*/
	if (time_after(jiffies, desc->last_unhandled + HZ/10))
	desc->irqs_unhandled = 1;
	else
	desc->irqs_unhandled++;
	desc->last_unhandled = jiffies;
	}

	irq = irq_desc_get_irq(desc);
	if (unlikely(try_misrouted_irq(irq, desc, action_ret))) {
	int ok = misrouted_irq(irq);
	if (action_ret == IRQ_NONE)
	desc->irqs_unhandled -= ok;
	}

	desc->irq_count++;
	if (likely(desc->irq_count < 100000))
	return;

	desc->irq_count = 0;
	if (unlikely(desc->irqs_unhandled > 99900)) {
	/*
	* The interrupt is stuck
	*/
	__report_bad_irq(desc, action_ret);
	/*
	* Now kill the IRQ
	*/
	printk(KERN_EMERG "Disabling IRQ #%d\n", irq);
	desc->istate \|= IRQS_SPURIOUS_DISABLED;
	desc->depth++;
	irq_disable(desc);

	mod_timer(&poll_spurious_irq_timer,
	jiffies + POLL_SPURIOUS_IRQ_INTERVAL);
	}
	desc->irqs_unhandled = 0;
	}

	bool noirqdebug __read_mostly;

	int noirqdebug_setup(char *str)
	{
	noirqdebug = 1;
	printk(KERN_INFO "IRQ lockup detection disabled\n");

	return 1;
	}

	__setup("noirqdebug", noirqdebug_setup);
	module_param(noirqdebug, bool, 0644);
	MODULE_PARM_DESC(noirqdebug, "Disable irq lockup detection when true");

	static int __init irqfixup_setup(char *str)
	{
	irqfixup = 1;
	printk(KERN_WARNING "Misrouted IRQ fixup support enabled.\n");
	printk(KERN_WARNING "This may impact system performance.\n");

	return 1;
	}

	__setup("irqfixup", irqfixup_setup);
	module_param(irqfixup, int, 0644);

	static int __init irqpoll_setup(char *str)
	{
	irqfixup = 2;
	printk(KERN_WARNING "Misrouted IRQ fixup and polling support "
	"enabled\n");
	printk(KERN_WARNING "This may significantly impact system "
	"performance\n");
	return 1;
	}

	__setup("irqpoll", irqpoll_setup);