Summary: A completeness theorem for a class of synchronization
Yehuda Afek Eytan Weisberger \Lambda
Hanan Weisman y
Computer Science Department, TelAviv University, Israel 69978.
We study a class of synchronization objects in shared
memory concurrent systems, which we call common2.
This class contains readmodifywrite objects that com
mute (e.g. fetchandadd), or overwrite (e.g. swap).
It is known that this class is contained in the consen
sus number 2 class of objects [Her91a], and most of the
commonly used objects with consensus number 2 are in
cluded in it. We show that any object in the common2
class can implement any other object in the class, in a
system with an arbitrary number of processes. In fact
we show that the objects in common2 are implementable
from any object with consensus number 2.
The common2 class is in particular interesting since