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.