  The question of whether all shared objects with consensus number 2 belong to
Common2, the set of objects that can be implemented in a wait-free manner by
any type of consensus number 2, was first posed by Herlihy. In the absence of
general results, several researchers have obtained implementations for
restricted-concurrency versions of FIFO queues. We present the first Common2
algorithm for a queue with two enqueuers and any number of dequeuers.
