LONG
InterlockedExchange(
IN OUT PLONG Target,
IN LONG Value
);
InterlockedExchange(a,b)能以原子操作的方式交换俩个参数a, b，并返回a以前的值；因为InterlockedExchange 是原子函数，不会要求中止中断，所以交换指针的方式是安全的。
假设有线程１和线程２调用ｆ（）函数，线程１先调用到InterlockedExchange(&g, TRUE);线程２再调用时，函数InterlockedExchange()总返回ＴＲＵＥ，则线程２sleep(0);而直到线程１调用InterlockedExchange(&g, FALSE);后线程２才可能由于调用InterlockedExchange(&g,, TRUE)，返回ＦＡＬＳＥ而退出循环接着工作。这样在//进行其他的操作这里就能操作共享数据而不会引起争议。当然这种方法会浪费ｃｐｕ时间，因为ｃｐｕ要不断地执行InterlockedExchange()函数，使用时应注意。
// 线程1
InterlockedExchange(&g, TRUE); // 步一
//..
InterlockedExchange(&g, FALSE); // 步三
//线程2
while(TRUE == InterlockedExchange(&g, TRUE))// 步二
{
sleep(0);
// 等待
}
// 线程2跳出循环了
// 步四
Windows Driver Kit: Kernel-Mode Driver Architecture
InterlockedExchange
The InterlockedExchange routine sets an integer variable to a given value as an atomic operation.
LONG
InterlockedExchange(
IN OUT PLONG Target,
IN LONG Value
);
Parameters
Target
-
Pointer to a variable to be set to the supplied
Value as an atomic operation.
Value
-
Specifies the value to which the variable will be set.
Return Value
InterlockedExchange returns the value of the variable at Target when the call occurred.
Headers
Declared in Wdm.h. Include Wdm.h, Ntddk.h, or Ntifs.h.
Comments
InterlockedExchange should be used instead of ExInterlockedExchangeUlong, because it is both faster and more efficient.
InterlockedExchange is implemented inline by the compiler when appropriate and possible. It does not require a spin lock and can therefore be safely used on pageable data.
A call to InterlockedExchange routine is atomic only with respect to other InterlockedXxx calls.
Interlocked operations cannot be used on non-cached memory.
Callers of InterlockedExchange can be running at any IRQL.
