// SPDX-License-Identifier: GPL-2.0
/*
 * 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/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(struct timer_list *unused);
static DEFINE_TIMER(poll_spurious_irq_timer, poll_spurious_irqs);
int irq_poll_cpu;
static atomic_t irq_poll_active;

/*
 * Recovery handler for misrouted interrupts.
 */
static bool try_one_irq(struct irq_desc *desc, bool force)
{
        struct irqaction *action;
        bool ret = false;

        guard(raw_spinlock)(&desc->lock);

        /*
         * PER_CPU, nested thread interrupts and interrupts explicitly
         * marked polled are excluded from polling.
         */
        if (irq_settings_is_per_cpu(desc) || irq_settings_is_nested_thread(desc) ||
            irq_settings_is_polled(desc))
                return false;

        /*
         * Do not poll disabled interrupts unless the spurious
         * disabled poller asks explicitly.
         */
        if (irqd_irq_disabled(&desc->irq_data) && !force)
                return false;

        /*
         * 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))
                return false;

        /* 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;
                return false;
        }

        /* Mark it poll in progress */
        desc->istate |= IRQS_POLL_INPROGRESS;
        do {
                if (handle_irq_event(desc) == IRQ_HANDLED)
                        ret = true;
                /* Make sure that there is still a valid action */
                action = desc->action;
        } while ((desc->istate & IRQS_PENDING) && action);
        desc->istate &= ~IRQS_POLL_INPROGRESS;
        return ret;
}

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(struct timer_list *unused)
{
        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 = READ_ONCE(desc->istate);
                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;

        if (bad_action_ret(action_ret))
                pr_err("irq event %d: bogus return value %x\n", irq, action_ret);
        else
                pr_err("irq %d: nobody cared (try booting with the \"irqpoll\" option)\n", irq);
        dump_stack();
        pr_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().
         */
        guard(raw_spinlock_irqsave)(&desc->lock);
        for_each_action_of_desc(desc, action) {
                pr_err("[<%p>] %ps", action->handler, action->handler);
                if (action->thread_fn)
                        pr_cont(" threaded [<%p>] %ps", action->thread_fn, action->thread_fn);
                pr_cont("\n");
        }
}

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 bool try_misrouted_irq(unsigned int irq, struct irq_desc *desc,
                                     irqreturn_t action_ret)
{
        struct irqaction *action;

        if (!irqfixup)
                return false;

        /* We didn't actually handle the IRQ - see if it was misrouted? */
        if (action_ret == IRQ_NONE)
                return true;

        /*
         * 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 false;

        if (!irq)
                return true;

        /*
         * Since we don't get the descriptor lock, "action" can
         * change under us.
         */
        action = READ_ONCE(desc->action);
        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 successfully
         * 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;
        }

        if (likely(!desc->irqs_unhandled))
                return;

        /* Now getting into unhandled irq detection */
        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
                 */
                pr_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;
        pr_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)
{
        if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
                pr_warn("irqfixup boot option not supported with PREEMPT_RT\n");
                return 1;
        }
        irqfixup = 1;
        pr_warn("Misrouted IRQ fixup support enabled.\n");
        pr_warn("This may impact system performance.\n");
        return 1;
}
__setup("irqfixup", irqfixup_setup);
module_param(irqfixup, int, 0644);

static int __init irqpoll_setup(char *str)
{
        if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
                pr_warn("irqpoll boot option not supported with PREEMPT_RT\n");
                return 1;
        }
        irqfixup = 2;
        pr_warn("Misrouted IRQ fixup and polling support enabled\n");
        pr_warn("This may significantly impact system performance\n");
        return 1;
}
__setup("irqpoll", irqpoll_setup);