spurious.c

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/*
 * 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(int irq, struct irq_desc *desc, bool force)
{
    irqreturn_t ret = IRQ_NONE;
    struct irqaction *action;

    raw_spin_lock(&desc->lock);

    /* PER_CPU and nested thread interrupts are never polled */
    if (irq_settings_is_per_cpu(desc) || irq_settings_is_nested_thread(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. Check for action->next as well.
     */
    action = desc->action;
    if (!action || !(action->flags & IRQF_SHARED) ||
        (action->flags & __IRQF_TIMER) ||
        (action->handler(irq, action->dev_id) == IRQ_HANDLED) ||
        !action->next)
        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;
        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(i, 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(i, 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)
{
    if (likely(action_ret <= (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(unsigned int irq, struct irq_desc *desc,
         irqreturn_t action_ret)
{
    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);
    action = desc->action;
    while (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");
        action = action->next;
    }
    raw_spin_unlock_irqrestore(&desc->lock, flags);
}

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

    if (count > 0) {
        count--;
        __report_bad_irq(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);
}

void note_interrupt(unsigned int irq, struct irq_desc *desc,
            irqreturn_t action_ret)
{
    if (desc->istate & IRQS_POLL_INPROGRESS)
        return;

    /* we get here again via the threaded handler */
    if (action_ret == IRQ_WAKE_THREAD)
        return;

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

    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;
    }

    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(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);