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 int handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
  80                                 struct irqaction *action)
  81 {
  82         int ret, retval = 0, status = 0;
  83
  84         if (!(action->flags & SA_INTERRUPT))
  85                 local_irq_enable();
  86
  87         do {
  88                 ret = action->handler(irq, action->dev_id, regs);
  89                 if (ret == IRQ_HANDLED)
  90                         status |= action->flags;
  91                 retval |= ret;
  92                 action = action->next;
  93         } while (action);
  94
  95         if (status & SA_SAMPLE_RANDOM)
  96                 add_interrupt_randomness(irq);
  97         local_irq_disable();
  98
  99         return retval;
 100 }
 101
 102 /*
 103  * do_IRQ handles all normal device IRQ's (the special
 104  * SMP cross-CPU interrupts have their own specific
 105  * handlers).
 106  */
 107 fastcall unsigned int __do_IRQ(unsigned int irq, struct pt_regs *regs)
 108 {
 109         irq_desc_t *desc = irq_desc + irq;
 110         struct irqaction * action;
 111         unsigned int status;
 112
 113         kstat_this_cpu.irqs[irq]++;
 114         if (desc->status & IRQ_PER_CPU) {
 115                 irqreturn_t action_ret;
 116
 117                 /*
 118                  * No locking required for CPU-local interrupts:
 119                  */
 120                 desc->handler->ack(irq);
 121                 action_ret = handle_IRQ_event(irq, regs, desc->action);
 122                 if (!noirqdebug)
 123                         note_interrupt(irq, desc, action_ret);
 124                 desc->handler->end(irq);
 125                 return 1;
 126         }
 127
 128         spin_lock(&desc->lock);
 129         desc->handler->ack(irq);
 130         /*
 131          * REPLAY is when Linux resends an IRQ that was dropped earlier
 132          * WAITING is used by probe to mark irqs that are being tested
 133          */
 134         status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
 135         status |= IRQ_PENDING; /* we _want_ to handle it */
 136
 137         /*
 138          * If the IRQ is disabled for whatever reason, we cannot
 139          * use the action we have.
 140          */
 141         action = NULL;
 142         if (likely(!(status & (IRQ_DISABLED | IRQ_INPROGRESS)))) {
 143                 action = desc->action;
 144                 status &= ~IRQ_PENDING; /* we commit to handling */
 145                 status |= IRQ_INPROGRESS; /* we are handling it */
 146         }
 147         desc->status = status;
 148
 149         /*
 150          * If there is no IRQ handler or it was disabled, exit early.
 151          * Since we set PENDING, if another processor is handling
 152          * a different instance of this same irq, the other processor
 153          * will take care of it.
 154          */
 155         if (unlikely(!action))
 156                 goto out;
 157
 158         /*
 159          * Edge triggered interrupts need to remember
 160          * pending events.
 161          * This applies to any hw interrupts that allow a second
 162          * instance of the same irq to arrive while we are in do_IRQ
 163          * or in the handler. But the code here only handles the _second_
 164          * instance of the irq, not the third or fourth. So it is mostly
 165          * useful for irq hardware that does not mask cleanly in an
 166          * SMP environment.
 167          */
 168         for (;;) {
 169                 irqreturn_t action_ret;
 170
 171                 spin_unlock(&desc->lock);
 172
 173                 action_ret = handle_IRQ_event(irq, regs, action);
 174
 175                 spin_lock(&desc->lock);
 176                 if (!noirqdebug)
 177                         note_interrupt(irq, desc, action_ret);
 178                 if (likely(!(desc->status & IRQ_PENDING)))
 179                         break;
 180                 desc->status &= ~IRQ_PENDING;
 181         }
 182         desc->status &= ~IRQ_INPROGRESS;
 183
 184 out:
 185         /*
 186          * The ->end() handler has to deal with interrupts which got
 187          * disabled while the handler was running.
 188          */
 189         desc->handler->end(irq);
 190         spin_unlock(&desc->lock);
 191
 192         return 1;
 193 }
 194