handle.c

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/*
 * 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"

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;
}