中断处理函数中不用disable_irq而用disable_irq_nosync原因【转】

/**
*    disable_irq_nosync - disable an irq without waiting
*    @irq: Interrupt to disable
*
*    Disable the selected interrupt line. Disablesand Enables are
*    nested.
*    Unlike disable_irq(),this function doesnot ensure existing
*    instances of the IRQ handler have completed before returning.
*
*    This function may be called from IRQ context.
*/
void disable_irq_nosync(unsigned int irq)
{
    struct irq_desc *desc = irq_to_desc(irq);
    unsigned long flags;

    if (!desc)
        return;

    chip_bus_lock(irq, desc);
    spin_lock_irqsave(&desc->lock, flags);
    __disable_irq(desc, irq, false);
    spin_unlock_irqrestore(&desc->lock, flags);
    chip_bus_sync_unlock(irq, desc);
}

/**
* disable_irq - disable an irq and wait for completion
* @irq: Interrupt to disable
*
* Disable the selected interrupt line. Enables and Disables are
* nested.
* This function waits for any pending IRQ handlers for this interrupt
* to complete before returning. If you use this function while
* holding a resource the IRQ handler may need you will deadlock.
*
* This function may be called - with care - from IRQ context.
*/
void disable_irq(unsignedint irq)
{
        struct irq_desc *desc = irq_desc + irq;
        if (irq>= NR_IRQS)
                return;
        disable_irq_nosync(irq);
        if (desc->action)
                synchronize_irq(irq);
}


/**
* synchronize_irq - wait for pending IRQ handlers (on other CPUs)
* @irq: interrupt number to wait for
*
* This function waits for any pending IRQ handlers for this interrupt
* to complete before returning. If you use this function while
* holding a resource the IRQ handler may need you will deadlock.
*
* This function may be called - with care - from IRQ context.
*/
void synchronize_irq(unsignedint irq)
{
struct irq_desc *desc= irq_to_desc(irq);
unsigned int status;
if (!desc)
  return;
do {
  unsigned long flags;
  /*
   * Wait until we're out of the critical section. This might
   * give the wrong answer due to the lack of memory barriers.
   */
  while (desc->status& IRQ_INPROGRESS)
   cpu_relax();
  /* Ok, that indicated we're done: double-check carefully. */
  spin_lock_irqsave(&desc->lock, flags);
  status = desc->status;
  spin_unlock_irqrestore(&desc->lock, flags);
  /* Oops, that failed? */
} while (status & IRQ_INPROGRESS);
/*
  * We made sure that no hardirq handler is running. Now verify
  * that no threaded handlers are active.
  */
wait_event(desc->wait_for_threads,!atomic_read(&desc->threads_active));
}