Migrating Protocols In Multi-Threaded Message-Passing Systems

Dynamic software update is a technique by which a running program can be updated with new code and data without interrupting its execution. Often we will want to preserve properties of programs across update boundaries. Preserving simple typing across update boundaries for single-threaded programs is well studied. There are other higher-level properties we may wish to preserve, particularly for multi-threaded programs. Session typing is used to guarantee that a set of parallel threads communicate according to a given protocol. Hence we investigate preserving correct communications behaviour of a set of parallel threads correctly across update boundaries which change the running protocol. We present a procedure for updating multiple threads to cleanly migrate a system from one protocol to another.