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                 .handler = &no_irq_type,
  34                 .lock = SPIN_LOCK_UNLOCKED
  35         }
  36 };
  37
  38 /*
  39  * Generic 'no controller' code
  40  */
  41 static void end_none(unsigned int irq) { }
  42 static void enable_none(unsigned int irq) { }
  43 static void disable_none(unsigned int irq) { }
  44 static void shutdown_none(unsigned int irq) { }
  45 static unsigned int startup_none(unsigned int irq) { return 0; }
  46
  47 static void ack_none(unsigned int irq)
  48 {
  49         /*
  50          * 'what should we do if we get a hw irq event on an illegal vector'.
  51          * each architecture has to answer this themself.
  52          */
  53         ack_bad_irq(irq);
  54 }
  55
  56 struct hw_interrupt_type no_irq_type = {
  57         .typename =     "none",
  58         .startup =      startup_none,
  59         .shutdown =     shutdown_none,
  60         .enable =       enable_none,
  61         .disable =      disable_none,
  62         .ack =          ack_none,
  63         .end =          end_none,
  64         .set_affinity = NULL
  65 };
  66
  67 /*
  68  * Special, empty irq handler:
  69  */
  70 irqreturn_t no_action(int cpl, void *dev_id, struct pt_regs *regs)
  71 {
  72         return IRQ_NONE;
  73 }
  74
  75 /*
  76  * Have got an event to handle:
  77  */
  78 fastcall int handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
  79                                 struct irqaction *action)
  80 {
  81         int ret, retval = 0, status = 0;
  82
  83         if (!(action->flags & SA_INTERRUPT))
  84                 local_irq_enable();
  85
  86         do {
  87                 ret = action->handler(irq, action->dev_id, regs);
  88                 if (ret == IRQ_HANDLED)
  89                         status |= action->flags;
  90                 retval |= ret;
  91                 action = action->next;
  92         } while (action);
  93
  94         if (status & SA_SAMPLE_RANDOM)
  95                 add_interrupt_randomness(irq);
  96         local_irq_disable();
  97
  98         return retval;
  99 }
 100
 101 /*
 102  * do_IRQ handles all normal device IRQ's (the special
 103  * SMP cross-CPU interrupts have their own specific
 104  * handlers).
 105  */
 106 fastcall unsigned int __do_IRQ(unsigned int irq, struct pt_regs *regs)
 107 {
 108         irq_desc_t *desc = irq_desc + irq;
 109         struct irqaction * action;
 110         unsigned int status;
 111
 112         kstat_this_cpu.irqs[irq]++;
 113         if (desc->status & IRQ_PER_CPU) {
 114                 irqreturn_t action_ret;
 115
 116                 /*
 117                  * No locking required for CPU-local interrupts:
 118                  */
 119                 desc->handler->ack(irq);
 120                 action_ret = handle_IRQ_event(irq, regs, desc->action);
 121                 if (!noirqdebug)
 122                         note_interrupt(irq, desc, action_ret);
 123                 desc->handler->end(irq);
 124                 return 1;
 125         }
 126
 127         spin_lock(&desc->lock);
 128         desc->handler->ack(irq);
 129         /*
 130          * REPLAY is when Linux resends an IRQ that was dropped earlier
 131          * WAITING is used by probe to mark irqs that are being tested
 132          */
 133         status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
 134         status |= IRQ_PENDING; /* we _want_ to handle it */
 135
 136         /*
 137          * If the IRQ is disabled for whatever reason, we cannot
 138          * use the action we have.
 139          */
 140         action = NULL;
 141         if (likely(!(status & (IRQ_DISABLED | IRQ_INPROGRESS)))) {
 142                 action = desc->action;
 143                 status &= ~IRQ_PENDING; /* we commit to handling */
 144                 status |= IRQ_INPROGRESS; /* we are handling it */
 145         }
 146         desc->status = status;
 147
 148         /*
 149          * If there is no IRQ handler or it was disabled, exit early.
 150          * Since we set PENDING, if another processor is handling
 151          * a different instance of this same irq, the other processor
 152          * will take care of it.
 153          */
 154         if (unlikely(!action))
 155                 goto out;
 156
 157         /*
 158          * Edge triggered interrupts need to remember
 159          * pending events.
 160          * This applies to any hw interrupts that allow a second
 161          * instance of the same irq to arrive while we are in do_IRQ
 162          * or in the handler. But the code here only handles the _second_
 163          * instance of the irq, not the third or fourth. So it is mostly
 164          * useful for irq hardware that does not mask cleanly in an
 165          * SMP environment.
 166          */
 167         for (;;) {
 168                 irqreturn_t action_ret;
 169
 170                 spin_unlock(&desc->lock);
 171
 172                 action_ret = handle_IRQ_event(irq, regs, action);
 173
 174                 spin_lock(&desc->lock);
 175                 if (!noirqdebug)
 176                         note_interrupt(irq, desc, action_ret);
 177                 if (likely(!(desc->status & IRQ_PENDING)))
 178                         break;
 179                 desc->status &= ~IRQ_PENDING;
 180         }
 181         desc->status &= ~IRQ_INPROGRESS;
 182
 183 out:
 184         /*
 185          * The ->end() handler has to deal with interrupts which got
 186          * disabled while the handler was running.
 187          */
 188         desc->handler->end(irq);
 189         spin_unlock(&desc->lock);
 190
 191         return 1;
 192 }
 193