WaitableTimer 的特殊之处

#define _SECOND 10000000

//回调函数
VOID CALLBACK TimerAPCProc(LPVOID lpArg,DWORD dwTimerLowValue,DWORD dwTimerHighValue )
{
printf("Timer was signaled.\n");
}

int _tmain(int argc, _TCHAR* argv[])
{

LARGE_INTEGER liDueTime;

//创建WaitableTimer
HANDLE hTimer = CreateWaitableTimer(NULL, TRUE, NULL);
if(hTimer)
{
//2秒后启用
liDueTime.QuadPart = -2 * _SECOND;
//设置计时器属性
int result = SetWaitableTimer(hTimer,&liDueTime,1000,TimerAPCProc,NULL,FALSE);
if(0< result)
{
printf("Waiting for 2 seconds...\n");
while(true) //如果此处不循环调用Ex函数，是不执行回调函数的
{
/*SleepEx(INFINITE, TRUE);*/
WaitForSingleObjectEx(hTimer, INFINITE,TRUE); //调用SleepEx和WaitForSingleObjectEx效果等效
}
}
}
return 0;

}

         查MSDN，才搞明白：

         线程必须是由于调用 SleepEX,WaitForSingleObjectEx,WaitForMultipleObjectsEX,MSGWaitForMultipleObjectsEx 或 SignalObjectAndWait而进入等待的状态。否则，系统不会把计时器的APC函数添加到队列中。

          This thread must be in an alertable state to execute the completion routine. It accomplishes this by calling the SleepEx function, which is an alertable function.