火车的家

//觉得很奇怪，既然电平中断一开始就mask了中断，
//退出的时候才unmask，怎么会与同类型的其他中断冲突呢？
void
handle_level_irq(unsigned int irq, struct irq_desc *desc)
{
    struct irqaction *action;
    irqreturn_t action_ret;

    spin_lock(&desc->lock);
    //一开始以为对于电平中断ack不会被调用，但是发现
    //mask_ack_irq会间接调用ack
    mask_ack_irq(desc, irq);

    if (unlikely(desc->status & IRQ_INPROGRESS))
        goto out_unlock;
    desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
    kstat_incr_irqs_this_cpu(irq, desc);

    /*
     * If its disabled or no action available
     * keep it masked and get out of here
     */
    action = desc->action;
    if (unlikely(!action || (desc->status & IRQ_DISABLED)))
        goto out_unlock;

    desc->status |= IRQ_INPROGRESS;
    spin_unlock(&desc->lock);

    action_ret = handle_IRQ_event(irq, action);
    if (!noirqdebug)
        note_interrupt(irq, desc, action_ret);

    spin_lock(&desc->lock);
    desc->status &= ~IRQ_INPROGRESS;

    if (unlikely(desc->status & IRQ_ONESHOT))
        desc->status |= IRQ_MASKED;
    else if (!(desc->status & IRQ_DISABLED) && desc->chip->unmask)
        desc->chip->unmask(irq);
out_unlock:
    spin_unlock(&desc->lock);
}
EXPORT_SYMBOL_GPL(handle_level_irq);

void
handle_edge_irq(unsigned int irq, struct irq_desc *desc)
{
    spin_lock(&desc->lock);

    desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);

    /*
     * If we're currently running this IRQ, or its disabled,
     * we shouldn't process the IRQ. Mark it pending, handle
     * the necessary masking and go out
     */
    //如注释中所说，在一个中断没有处理完时，如果该中断又被触发，则这个中断会被标记
    //为阻塞然后被屏蔽。
    //注意：只有在这种情况或者中断被设置了IRQ_DISABLED的情况下才会屏蔽中断，否则该
    //中断不会被屏蔽。
    //其实，对于中断来说，第一次被触发时，不会屏蔽该中断，如果在这个中断的处理过程
    //中又有中断被触发，则这个中断会被标记为阻塞并且屏蔽该中断。这么做的目的是，提