local_irq_disable()分析

local_irq_disable()用来禁止本地cpu的中断;

local_irq_disable()  

函数主要干了两件事情：

#define local_irq_disable() \
        do { raw_local_irq_disable(); trace_hardirqs_off(); } while (0)

 

static void (void)

{

        unsigned long = ();

        (( & ~) | );

}

保存cpu flags的值;当中断处理程序返回是再恢复到寄存器中;
2) trace_hardirqs_off();

 

void (void)

{

        struct  *curr = current;

        if ((! || current->lockdep_recursion))

                return;

        if ((!()))

                return;

        if (curr->) {

                /*

                 * We have done an ON -> OFF transition:

                 */

                curr-> = 0;

                curr-> = ;

                curr-> = ++curr->;

                (&);

        } else

                (&);

}

：

可以看到经过系列的判断，最终的操作还是集中在 ： if (curr->):
如果硬件断是打开的,则对struct  *curr = current;执行后面的一系列操作:
  = 0;,硬件中断关标志,
  =  此项记录的应该是引起中断的进程;
 = ++curr->;则是记录的引起中断发生的事件;
以上操作将硬件中断关掉.

一些关于原子操作的....

 * @v: pointer of type atomic_t

 * 

 * Atomically adds @i to @v.

 */

static  void (int ,  *)

{

         (

                 "addl %1,%0"

                :"+m" (->)

                :"ir" ());

}

其中lock是一个指令前缀，Intel的手册上对其的解释是：

Causes the processor's LOCK# signal to be asserted during execution of the accompanying instruction (turns the instruction into an atomic instruction). In a multiprocessor environment, the LOCK# signal insures that the processor has exclusive use of any shared memory while the signal is asserted.

也就是说lock会使紧跟在其后面的指令变成 atomic instruction。在执行该指令是暂时的锁一下总线，
指令执行完了，总线就解锁了！ 相同的如static  void (int ,  *)等对
整型原子数的操作都是通过 lock 前缀来实现的;