linux中断（4）：中断处理流程之 handle_irq_event

handle_edge_irq，handle_level_irq等函数会调用handle_irq_event，我们来看一下它的流程
handle_irq_event->handle_irq_event_percpu->action->handler

irqreturn_t handle_irq_event(struct irq_desc *desc)
{
 struct irqaction *action = desc->action;
 irqreturn_t ret;

 desc->istate &= ~IRQS_PENDING;
 irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);  /* 设置IRQD_IRQ_INPROGRESS标志，防止同一中断isr嵌套执行*/
 raw_spin_unlock(&desc->lock);

 ret = handle_irq_event_percpu(desc, action);

 raw_spin_lock(&desc->lock);
 irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);/* 清除IRQD_IRQ_INPROGRESS标志 */

 return ret;
}

irqreturn_t
handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
{
 irqreturn_t retval = IRQ_NONE;
 unsigned int flags = 0, irq = desc->irq_data.irq;

 trace_irq_entry(irq, NULL, action);

 do {
  irqreturn_t res;

  trace_irq_handler_entry(irq, action);
  res = action->handler(irq, action->dev_id); /* 调用action->handler，即request_irq 时注册的handler 函数 */
  trace_irq_handler_exit(irq, action, res);

  if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
         irq, action->handler))
   local_irq_disable();

  switch (res) {
  case IRQ_WAKE_THREAD:  /*  线程化的中断通常返回这个值 IRQ_WAKE_THREAD */
   /*
    * Catch drivers which return WAKE_THREAD but
    * did not set up a thread function
    */
   if (unlikely(!action->thread_fn)) {
    warn_no_thread(irq, action);
    break;
   }

   irq_wake_thread(desc, action);  /* 唤醒线程化的中断线程 */

   /* Fall through to add to randomness */
  case IRQ_HANDLED:
   flags |= action->flags;
   break;

  default:
   break;
  }

  retval |= res;
  action = action->next; /* 如果共享中断，则需要循环执行action链表上的action   */
 } while (action);

 add_interrupt_randomness(irq, flags);

 if (!noirqdebug)
  note_interrupt(irq, desc, retval);

 trace_irq_exit(retval);

 return retval;
}