ip stack mutual exclusion

[Fermi at aol.com]

I am adding a security association database to the
RTEMS IP-stack to support IPSEC. 

I would like to run RTEMS with a 
thread time slice, but a thread that is acessing the database when its time quantum expires might leave 
it in an unstable state.

In unix to suport mutual exclusion a programmer raises and then replaces the interupt levels with calls to spl***() and splx(). 

RTEMS has #defined spl***() and splx() to do nothing. 

How can I support a mutual exclusion in the RTEMS IP stack? Will a semaphore work?