filedisk

I am studing the filedisk source code.
I want to know the reason why there hasn\'t IoAttachDeviceToDeviceStack  behind IoCreateDevice .

In the function of FileDiskThread,it wait for request_event,
I want to know where the request_event is seted signed .
In the filedisk.
it call \" KeSetEvent(&device_extension->request_event,(KPRIORITY) 0,FALSE);\" five times,        
but hasn\'t call
\" KeSetEvent(&device_extension->request_event,(KPRIORITY) 0,
TRUE);\"              
            
My filedisk project include filedisk.c and filedisk.h.
The version of file is 1,0,0,7