text: /*
   * 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);
  