使用overlap时，为什么有时会出错，有时又正确通过？附代码如下

int usb_read(HANDLE h_read,void* buffer,int size,int *p_count)
{
int ret_code=SUCCESS;
OVERLAPPED lc_overlap;
DWORD ret_count;

memset(buffer,0,size);

lc_overlap.hEvent=CreateEvent(NULL,true,false,NULL);

if(!ReadFile(h_read,buffer,size,(PDWORD)p_count,&lc_overlap))
{
if(GetLastError()==ERROR_IO_PENDING)
{
ret_count=WaitForSingleObject(lc_overlap.hEvent,TIMEOUT);
if(ret_count==WAIT_TIMEOUT)
{
CancelIo(h_read);
ret_code=ETIMEOUT;
}
}
else
{
DeviceIoControl(h_read,IOCTL_JBCJ_RESET_PIPE,0,0,0,0,&ret_count,&lc_overlap);
ret_code=EUSB_READ_FAIL;
}
}

GetOverlappedResult(h_read,&lc_overlap,(PDWORD)p_count,false);
CloseHandle(lc_overlap.hEvent);
return ret_code;
}


报参数不对。但我保证参数不会有问题。
GetLastError()返回87，并且我观察过，驱动里根本就没有接收到此请求。