kernel/irq/handle.c

   1 /*
   2  * linux/kernel/irq/handle.c
   3  *
   4  * Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
   5  *
   6  * This file contains the core interrupt handling code.
   7  */
   8
   9 #include <linux/irq.h>
  10 #include <linux/module.h>
  11 #include <linux/random.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/kernel_stat.h>
  14
  15 #include "internals.h"
  16
  17 /*
  18  * Linux has a controller-independent interrupt architecture.
  19  * Every controller has a 'controller-template', that is used
  20  * by the main code to do the right thing. Each driver-visible
  21  * interrupt source is transparently wired to the apropriate
  22  * controller. Thus drivers need not be aware of the
  23  * interrupt-controller.
  24  *
  25  * The code is designed to be easily extended with new/different
  26  * interrupt controllers, without having to do assembly magic or
  27  * having to touch the generic code.
  28  *
  29  * Controller mappings for all interrupt sources:
  30  */
  31 irq_desc_t irq_desc[NR_IRQS] __cacheline_aligned = {
  32         [0 ... NR_IRQS-1] = {
  33                 .status = IRQ_DISABLED,
  34                 .handler = &no_irq_type,
  35                 .lock = SPIN_LOCK_UNLOCKED
  36         }
  37 };
  38
  39 /*
  40  * Generic 'no controller' code
  41  */
  42 static void end_none(unsigned int irq) { }
  43 static void enable_none(unsigned int irq) { }
  44 static void disable_none(unsigned int irq) { }
  45 static void shutdown_none(unsigned int irq) { }
  46 static unsigned int startup_none(unsigned int irq) { return 0; }
  47
  48 static void ack_none(unsigned int irq)
  49 {
  50         /*
  51          * 'what should we do if we get a hw irq event on an illegal vector'.
  52          * each architecture has to answer this themself.
  53          */
  54         ack_bad_irq(irq);
  55 }
  56
  57 struct hw_interrupt_type no_irq_type = {
  58         .typename =     "none",
  59         .startup =      startup_none,
  60         .shutdown =     shutdown_none,
  61         .enable =       enable_none,
  62         .disable =      disable_none,
  63         .ack =          ack_none,
  64         .end =          end_none,
  65         .set_affinity = NULL
  66 };
  67
  68 /*
  69  * Special, empty irq handler:
  70  */
  71 irqreturn_t no_action(int cpl, void *dev_id, struct pt_regs *regs)
  72 {
  73         return IRQ_NONE;
  74 }
  75
  76 /*
  77  * Have got an event to handle:
  78  */
  79 fastcall irqreturn_t handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
  80                                 struct irqaction *action)
  81 {
  82         irqreturn_t ret, retval = IRQ_NONE;
  83         unsigned int status = 0;
  84
  85         if (!(action->flags & SA_INTERRUPT))
  86                 local_irq_enable();
  87
  88         do {
  89                 ret = action->handler(irq, action->dev_id, regs);
  90                 if (ret == IRQ_HANDLED)
  91                         status |= action->flags;
  92                 retval |= ret;
  93                 action = action->next;
  94         } while (action);
  95
  96         if (status & SA_SAMPLE_RANDOM)
  97                 add_interrupt_randomness(irq);
  98         local_irq_disable();
  99
 100         return retval;
 101 }
 102
 103 /*
 104  * do_IRQ handles all normal device IRQ's (the special
 105  * SMP cross-CPU interrupts have their own specific
 106  * handlers).
 107  */
 108 fastcall unsigned int __do_IRQ(unsigned int irq, struct pt_regs *regs)
 109 {
 110         irq_desc_t *desc = irq_desc + irq;
 111         struct irqaction * action;
 112         unsigned int status;
 113
 114         kstat_this_cpu.irqs[irq]++;
 115         if (CHECK_IRQ_PER_CPU(desc->status)) {
 116                 irqreturn_t action_ret;
 117
 118                 /*
 119                  * No locking required for CPU-local interrupts:
 120                  */
 121                 if (desc->handler->ack)
 122                         desc->handler->ack(irq);
 123                 action_ret = handle_IRQ_event(irq, regs, desc->action);
 124                 desc->handler->end(irq);
 125                 return 1;
 126         }
 127
 128         spin_lock(&desc->lock);
 129         if (desc->handler->ack)
 130                 desc->handler->ack(irq);
 131         /*
 132          * REPLAY is when Linux resends an IRQ that was dropped earlier
 133          * WAITING is used by probe to mark irqs that are being tested
 134          */
 135         status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
 136         status |= IRQ_PENDING; /* we _want_ to handle it */
 137
 138         /*
 139          * If the IRQ is disabled for whatever reason, we cannot
 140          * use the action we have.
 141          */
 142         action = NULL;
 143         if (likely(!(status & (IRQ_DISABLED | IRQ_INPROGRESS)))) {
 144                 action = desc->action;
 145                 status &= ~IRQ_PENDING; /* we commit to handling */
 146                 status |= IRQ_INPROGRESS; /* we are handling it */
 147         }
 148         desc->status = status;
 149
 150         /*
 151          * If there is no IRQ handler or it was disabled, exit early.
 152          * Since we set PENDING, if another processor is handling
 153          * a different instance of this same irq, the other processor
 154          * will take care of it.
 155          */
 156         if (unlikely(!action))
 157                 goto out;
 158
 159         /*
 160          * Edge triggered interrupts need to remember
 161          * pending events.
 162          * This applies to any hw interrupts that allow a second
 163          * instance of the same irq to arrive while we are in do_IRQ
 164          * or in the handler. But the code here only handles the _second_
 165          * instance of the irq, not the third or fourth. So it is mostly
 166          * useful for irq hardware that does not mask cleanly in an
 167          * SMP environment.
 168          */
 169         for (;;) {
 170                 irqreturn_t action_ret;
 171
 172                 spin_unlock(&desc->lock);
 173
 174                 action_ret = handle_IRQ_event(irq, regs, action);
 175
 176                 spin_lock(&desc->lock);
 177                 if (!noirqdebug)
 178                         note_interrupt(irq, desc, action_ret, regs);
 179                 if (likely(!(desc->status & IRQ_PENDING)))
 180                         break;
 181                 desc->status &= ~IRQ_PENDING;
 182         }
 183         desc->status &= ~IRQ_INPROGRESS;
 184
 185 out:
 186         /*
 187          * The ->end() handler has to deal with interrupts which got
 188          * disabled while the handler was running.
 189          */
 190         desc->handler->end(irq);
 191         spin_unlock(&desc->lock);
 192
 193         return 1;
 194 }
 195