linux/kernel/irq/handle.c
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   1/*
   2 * linux/kernel/irq/handle.c
   3 *
   4 * Copyright (C) 1992, 1998-2006 Linus Torvalds, Ingo Molnar
   5 * Copyright (C) 2005-2006, Thomas Gleixner, Russell King
   6 *
   7 * This file contains the core interrupt handling code.
   8 *
   9 * Detailed information is available in Documentation/DocBook/genericirq
  10 *
  11 */
  12
  13#include <linux/irq.h>
  14#include <linux/random.h>
  15#include <linux/sched.h>
  16#include <linux/interrupt.h>
  17#include <linux/kernel_stat.h>
  18
  19#include <trace/events/irq.h>
  20
  21#include "internals.h"
  22
  23/**
  24 * handle_bad_irq - handle spurious and unhandled irqs
  25 * @irq:       the interrupt number
  26 * @desc:      description of the interrupt
  27 *
  28 * Handles spurious and unhandled IRQ's. It also prints a debugmessage.
  29 */
  30void handle_bad_irq(unsigned int irq, struct irq_desc *desc)
  31{
  32        print_irq_desc(irq, desc);
  33        kstat_incr_irqs_this_cpu(irq, desc);
  34        ack_bad_irq(irq);
  35}
  36
  37/*
  38 * Special, empty irq handler:
  39 */
  40irqreturn_t no_action(int cpl, void *dev_id)
  41{
  42        return IRQ_NONE;
  43}
  44
  45static void warn_no_thread(unsigned int irq, struct irqaction *action)
  46{
  47        if (test_and_set_bit(IRQTF_WARNED, &action->thread_flags))
  48                return;
  49
  50        printk(KERN_WARNING "IRQ %d device %s returned IRQ_WAKE_THREAD "
  51               "but no thread function available.", irq, action->name);
  52}
  53
  54static void irq_wake_thread(struct irq_desc *desc, struct irqaction *action)
  55{
  56        /*
  57         * In case the thread crashed and was killed we just pretend that
  58         * we handled the interrupt. The hardirq handler has disabled the
  59         * device interrupt, so no irq storm is lurking.
  60         */
  61        if (action->thread->flags & PF_EXITING)
  62                return;
  63
  64        /*
  65         * Wake up the handler thread for this action. If the
  66         * RUNTHREAD bit is already set, nothing to do.
  67         */
  68        if (test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags))
  69                return;
  70
  71        /*
  72         * It's safe to OR the mask lockless here. We have only two
  73         * places which write to threads_oneshot: This code and the
  74         * irq thread.
  75         *
  76         * This code is the hard irq context and can never run on two
  77         * cpus in parallel. If it ever does we have more serious
  78         * problems than this bitmask.
  79         *
  80         * The irq threads of this irq which clear their "running" bit
  81         * in threads_oneshot are serialized via desc->lock against
  82         * each other and they are serialized against this code by
  83         * IRQS_INPROGRESS.
  84         *
  85         * Hard irq handler:
  86         *
  87         *      spin_lock(desc->lock);
  88         *      desc->state |= IRQS_INPROGRESS;
  89         *      spin_unlock(desc->lock);
  90         *      set_bit(IRQTF_RUNTHREAD, &action->thread_flags);
  91         *      desc->threads_oneshot |= mask;
  92         *      spin_lock(desc->lock);
  93         *      desc->state &= ~IRQS_INPROGRESS;
  94         *      spin_unlock(desc->lock);
  95         *
  96         * irq thread:
  97         *
  98         * again:
  99         *      spin_lock(desc->lock);
 100         *      if (desc->state & IRQS_INPROGRESS) {
 101         *              spin_unlock(desc->lock);
 102         *              while(desc->state & IRQS_INPROGRESS)
 103         *                      cpu_relax();
 104         *              goto again;
 105         *      }
 106         *      if (!test_bit(IRQTF_RUNTHREAD, &action->thread_flags))
 107         *              desc->threads_oneshot &= ~mask;
 108         *      spin_unlock(desc->lock);
 109         *
 110         * So either the thread waits for us to clear IRQS_INPROGRESS
 111         * or we are waiting in the flow handler for desc->lock to be
 112         * released before we reach this point. The thread also checks
 113         * IRQTF_RUNTHREAD under desc->lock. If set it leaves
 114         * threads_oneshot untouched and runs the thread another time.
 115         */
 116        desc->threads_oneshot |= action->thread_mask;
 117
 118        /*
 119         * We increment the threads_active counter in case we wake up
 120         * the irq thread. The irq thread decrements the counter when
 121         * it returns from the handler or in the exit path and wakes
 122         * up waiters which are stuck in synchronize_irq() when the
 123         * active count becomes zero. synchronize_irq() is serialized
 124         * against this code (hard irq handler) via IRQS_INPROGRESS
 125         * like the finalize_oneshot() code. See comment above.
 126         */
 127        atomic_inc(&desc->threads_active);
 128
 129        wake_up_process(action->thread);
 130}
 131
 132irqreturn_t
 133handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
 134{
 135        irqreturn_t retval = IRQ_NONE;
 136        unsigned int flags = 0, irq = desc->irq_data.irq;
 137
 138        do {
 139                irqreturn_t res;
 140
 141                trace_irq_handler_entry(irq, action);
 142                res = action->handler(irq, action->dev_id);
 143                trace_irq_handler_exit(irq, action, res);
 144
 145                if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
 146                              irq, action->handler))
 147                        local_irq_disable();
 148
 149                switch (res) {
 150                case IRQ_WAKE_THREAD:
 151                        /*
 152                         * Catch drivers which return WAKE_THREAD but
 153                         * did not set up a thread function
 154                         */
 155                        if (unlikely(!action->thread_fn)) {
 156                                warn_no_thread(irq, action);
 157                                break;
 158                        }
 159
 160                        irq_wake_thread(desc, action);
 161
 162                        /* Fall through to add to randomness */
 163                case IRQ_HANDLED:
 164                        flags |= action->flags;
 165                        break;
 166
 167                default:
 168                        break;
 169                }
 170
 171                retval |= res;
 172                action = action->next;
 173        } while (action);
 174
 175        add_interrupt_randomness(irq, flags);
 176
 177        if (!noirqdebug)
 178                note_interrupt(irq, desc, retval);
 179        return retval;
 180}
 181
 182irqreturn_t handle_irq_event(struct irq_desc *desc)
 183{
 184        struct irqaction *action = desc->action;
 185        irqreturn_t ret;
 186
 187        desc->istate &= ~IRQS_PENDING;
 188        irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);
 189        raw_spin_unlock(&desc->lock);
 190
 191        ret = handle_irq_event_percpu(desc, action);
 192
 193        raw_spin_lock(&desc->lock);
 194        irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
 195        return ret;
 196}
 197
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