/*
 * 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/DocBook/genericirq
 *
 */

#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
 * @irq:       the interrupt number
 * @desc:      description of the interrupt
 *
 * Handles spurious and unhandled IRQ's. It also prints a debugmessage.
 */
void handle_bad_irq(unsigned int irq, struct irq_desc *desc)
{
        print_irq_desc(irq, desc);
        kstat_incr_irqs_this_cpu(irq, desc);
        ack_bad_irq(irq);
}

/*
 * Special, empty irq handler:
 */
irqreturn_t no_action(int cpl, void *dev_id)
{
        return IRQ_NONE;
}

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);
}

static 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);
}

irqreturn_t
handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
{
        irqreturn_t retval = IRQ_NONE;
        unsigned int flags = 0, irq = desc->irq_data.irq;

        do {
                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;
                action = action->next;
        } while (action);

        add_interrupt_randomness(irq, flags);

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

irqreturn_t handle_irq_event(struct irq_desc *desc)
{
        struct irqaction *action = desc->action;
        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, action);

        raw_spin_lock(&desc->lock);
        irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
        return ret;
}