Release 4.15 kernel/irq/handle.c

/*
 * linux/kernel/irq/handle.c
 *
 * Copyright (C) 1992, 1998-2006 Linus Torvalds, Ingo Molnar
 * Copyright (C) 2005-2006, Thomas Gleixner, Russell King
 *
 * This file contains the core interrupt handling code.
 *
 * Detailed information is available in Documentation/core-api/genericirq.rst
 *
 */

#include <linux/irq.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>

#include <trace/events/irq.h>

#include "internals.h"

/**
 * handle_bad_irq - handle spurious and unhandled irqs
 * @desc:      description of the interrupt
 *
 * Handles spurious and unhandled IRQ's. It also prints a debugmessage.
 */


void handle_bad_irq(struct irq_desc *desc)
{
	unsigned int irq = irq_desc_get_irq(desc);

	print_irq_desc(irq, desc);
	kstat_incr_irqs_this_cpu(desc);
	ack_bad_irq(irq);
}
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EXPORT_SYMBOL_GPL(handle_bad_irq);

/*
 * Special, empty irq handler:
 */


irqreturn_t no_action(int cpl, void *dev_id)
{
	return IRQ_NONE;
}
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EXPORT_SYMBOL_GPL(no_action);



static void warn_no_thread(unsigned int irq, struct irqaction *action)
{
	if (test_and_set_bit(IRQTF_WARNED, &action->thread_flags))
		return;

	printk(KERN_WARNING "IRQ %d device %s returned IRQ_WAKE_THREAD "
	       "but no thread function available.", irq, action->name);
}

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void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action)
{
	/*
         * In case the thread crashed and was killed we just pretend that
         * we handled the interrupt. The hardirq handler has disabled the
         * device interrupt, so no irq storm is lurking.
         */
	if (action->thread->flags & PF_EXITING)
		return;

	/*
         * Wake up the handler thread for this action. If the
         * RUNTHREAD bit is already set, nothing to do.
         */
	if (test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags))
		return;

	/*
         * It's safe to OR the mask lockless here. We have only two
         * places which write to threads_oneshot: This code and the
         * irq thread.
         *
         * This code is the hard irq context and can never run on two
         * cpus in parallel. If it ever does we have more serious
         * problems than this bitmask.
         *
         * The irq threads of this irq which clear their "running" bit
         * in threads_oneshot are serialized via desc->lock against
         * each other and they are serialized against this code by
         * IRQS_INPROGRESS.
         *
         * Hard irq handler:
         *
         *      spin_lock(desc->lock);
         *      desc->state |= IRQS_INPROGRESS;
         *      spin_unlock(desc->lock);
         *      set_bit(IRQTF_RUNTHREAD, &action->thread_flags);
         *      desc->threads_oneshot |= mask;
         *      spin_lock(desc->lock);
         *      desc->state &= ~IRQS_INPROGRESS;
         *      spin_unlock(desc->lock);
         *
         * irq thread:
         *
         * again:
         *      spin_lock(desc->lock);
         *      if (desc->state & IRQS_INPROGRESS) {
         *              spin_unlock(desc->lock);
         *              while(desc->state & IRQS_INPROGRESS)
         *                      cpu_relax();
         *              goto again;
         *      }
         *      if (!test_bit(IRQTF_RUNTHREAD, &action->thread_flags))
         *              desc->threads_oneshot &= ~mask;
         *      spin_unlock(desc->lock);
         *
         * So either the thread waits for us to clear IRQS_INPROGRESS
         * or we are waiting in the flow handler for desc->lock to be
         * released before we reach this point. The thread also checks
         * IRQTF_RUNTHREAD under desc->lock. If set it leaves
         * threads_oneshot untouched and runs the thread another time.
         */
	desc->threads_oneshot |= action->thread_mask;

	/*
         * We increment the threads_active counter in case we wake up
         * the irq thread. The irq thread decrements the counter when
         * it returns from the handler or in the exit path and wakes
         * up waiters which are stuck in synchronize_irq() when the
         * active count becomes zero. synchronize_irq() is serialized
         * against this code (hard irq handler) via IRQS_INPROGRESS
         * like the finalize_oneshot() code. See comment above.
         */
	atomic_inc(&desc->threads_active);

	wake_up_process(action->thread);
}

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irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc, unsigned int *flags)
{
	irqreturn_t retval = IRQ_NONE;
	unsigned int irq = desc->irq_data.irq;
	struct irqaction *action;

	record_irq_time(desc);

	for_each_action_of_desc(desc, action) {
		irqreturn_t res;

		trace_irq_handler_entry(irq, action);
		res = action->handler(irq, action->dev_id);
		trace_irq_handler_exit(irq, action, res);

		if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
			      irq, action->handler))
			local_irq_disable();

		switch (res) {
		case IRQ_WAKE_THREAD:
			/*
                         * Catch drivers which return WAKE_THREAD but
                         * did not set up a thread function
                         */
			if (unlikely(!action->thread_fn)) {
				warn_no_thread(irq, action);
				break;
			}

			__irq_wake_thread(desc, action);

			/* Fall through to add to randomness */
		case IRQ_HANDLED:
			*flags |= action->flags;
			break;

		default:
			break;
		}

		retval |= res;
	}

	return retval;
}

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irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
{
	irqreturn_t retval;
	unsigned int flags = 0;

	retval = __handle_irq_event_percpu(desc, &flags);

	add_interrupt_randomness(desc->irq_data.irq, flags);

	if (!noirqdebug)
		note_interrupt(desc, retval);
	return retval;
}

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irqreturn_t handle_irq_event(struct irq_desc *desc)
{
	irqreturn_t ret;

	desc->istate &= ~IRQS_PENDING;
	irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);
	raw_spin_unlock(&desc->lock);

	ret = handle_irq_event_percpu(desc);

	raw_spin_lock(&desc->lock);
	irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
	return ret;
}
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Directory: kernel/irq

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