An Alternate Concurrency Primitive
•Rather
than using the Test&Set to guard shared data, use Fetch&Add
•Fetch&Add is an atomic read-modify-write operation on
memory
-- requires special hardware, to be discussed
•Use
Fetch&Add as a semaphore and as a scheduler
•Operation: Fetch&Add(V,e)
•V is a
memory location
•e is
an integer expression
•Contents
of V are returned
•New
value of V is V+e
•Operation
is atomic
V: 0
Fetch&Add(V,1)
V: 1
0 is returned