关于中断处理程序中的关中断函数disable_irq和disable_irq_nosync

/**
*    disable_irq_nosync - disable an irq without waiting
*    @irq: Interrupt to disable
*
*    Disable the selected interrupt line. Disables and Enables are
*    nested.
*    Unlike disable_irq(), this function does not 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(unsigned int 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(unsigned int 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));
}