problem with 2 device objects

Iam writing a serial port filter driver.I have 2 device objects,the
extra device object is to track the IOCTLS from user
mode application (as given in DDK docs) and can get the data
from application.

I stored the data from app in a global variable
and tried to access it in my driver dispatch routines.But ended up
getting DRIVER_IRQL_NOT_LESS_OR_EQUAL error.I tried by declaring the
global variable in DEVICE EXTENSION,but then the variable data is not
getting updated.

Can anyone point me in right direction?

Thanks.

-Robert