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2.6.10的__do_irq:- /*
- * do_IRQ handles all normal device IRQ's (the special
- * SMP cross-CPU interrupts have their own specific
- * handlers).
- */
- fastcall unsigned int __do_IRQ(unsigned int irq, struct pt_regs *regs)
- {
- irq_desc_t *desc = irq_desc + irq;
- struct irqaction * action;
- unsigned int status;
- kstat_this_cpu.irqs[irq]++;
- if (desc->status & IRQ_PER_CPU) {
- irqreturn_t action_ret;
- /*
- * No locking required for CPU-local interrupts:
- */
- desc->handler->ack(irq);
- action_ret = handle_IRQ_event(irq, regs, desc->action);
- if (!noirqdebug)
- note_interrupt(irq, desc, action_ret);
- desc->handler->end(irq);
- return 1;
- }
- spin_lock(&desc->lock);
- desc->handler->ack(irq);
- /*
- * REPLAY is when Linux resends an IRQ that was dropped earlier
- * WAITING is used by probe to mark irqs that are being tested
- */
- status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
- status |= IRQ_PENDING; /* we _want_ to handle it */
- /*
- * If the IRQ is disabled for whatever reason, we cannot
- * use the action we have.
- */
- action = NULL;
- if (likely(!(status & (IRQ_DISABLED | IRQ_INPROGRESS)))) {
- action = desc->action;
- status &= ~IRQ_PENDING; /* we commit to handling */
- status |= IRQ_INPROGRESS; /* we are handling it */
- }
- desc->status = status;
- /*
- * If there is no IRQ handler or it was disabled, exit early.
- * Since we set PENDING, if another processor is handling
- * a different instance of this same irq, the other processor
- * will take care of it.
- */
- if (unlikely(!action))
- goto out;
- /*
- * Edge triggered interrupts need to remember
- * pending events.
- * This applies to any hw interrupts that allow a second
- * instance of the same irq to arrive while we are in do_IRQ
- * or in the handler. But the code here only handles the _second_
- * instance of the irq, not the third or fourth. So it is mostly
- * useful for irq hardware that does not mask cleanly in an
- * SMP environment.
- */
- for (;;) {
- irqreturn_t action_ret;
- spin_unlock(&desc->lock);
- action_ret = handle_IRQ_event(irq, regs, action);
- spin_lock(&desc->lock);
- if (!noirqdebug)
- note_interrupt(irq, desc, action_ret);
- if (likely(!(desc->status & IRQ_PENDING)))
- break;
- desc->status &= ~IRQ_PENDING;
- }
- desc->status &= ~IRQ_INPROGRESS;
- out:
- /*
- * The ->end() handler has to deal with interrupts which got
- * disabled while the handler was running.
- */
- desc->handler->end(irq);
- spin_unlock(&desc->lock);
- return 1;
- }
复制代码 注意到设置irq_pending标志位是有锁保护的,也就是说就算有中断发生也不会马上设置这个标志。也是顺序等待响应过之后才设置。 |
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