DeviceIoControl的异步问题

MSDN上讲DeviceIoControl时, 如果目标设备是用FILE_FLAG_OVERLAPPED标记打开, DeviceIoControl时必须指定一个有效的OVERLAPPED,
搞笑的是我指定一个OVERLAPPED时老返回false, GetLastError是ERROR_IO_PENDDING, 然后我Wait这个OVERLAPPED里的event对象时一直不返回, 如果直接给一个NULL而不指定OVERLAPPED反而能正确返回, 见鬼, MSDN不是说不指定就会fail吗?
原话如下, 请指点一下
If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, this parameter must point to a valid OVERLAPPED structure. In this case, DeviceIoControl is performed as an overlapped (asynchronous) operation. If the device was opened with FILE_FLAG_OVERLAPPED and lpOverlapped is NULL, the function fails in unpredictable ways.

返回PENDING说明驱动没有处理完请求，你等待event是对的，但你的event是否正确呢？

OVERLAPPED结构里的event,
OVERLAPPED ol;
...
ol.hEvent = myEvent; //myEvent是手动event, 全局变量
//专门用于这个DeviceIoControl, 别的地方不会用到
ResetEvent(myEvent);
BOOL bRet = DeviceIoControl(...., &ol);
....
WaitForSingleObject(myEvent, INFINITE); //永远死在这里
..

上面的代码有问题??

你把你的ol首先全部置零
memset( &ol, 0, sizeof( OVERLAPPED )
然后在ol.hEvent = myEvent;

呵呵，给分吧。