Section: New Results

Deterministic Concurrency: A Clock-Synchronised Shared Memory Approach

Participant : Marc Pouzet.

Synchronous programming (SP) provides deterministic concurrency. So far, however, communication has been constrained to a set of primitive clock-synchronised shared memory (scm) data types, such as data-flow registers, streams and signals with restricted read and write accesses that limit modularity and behavioural abstractions. In the paper [23], we propose an extension to the SP theory which retains the advantages of deterministic concurrency, but allows communication to occur at higher levels of abstraction than currently supported by SP data types. Our approach is as follows. To avoid data races, each csm type publishes a policy interface for specifying the admissibility and precedence of its access methods. Each instance of the csm type has to be policy-coherent, meaning it must behave deterministically under its own policy—a natural requirement if the goal is to build deterministic sys- tems that use these types. In a policy-constructive system, all access methods can be scheduled in a policy-conformant way for all the types without deadlocking. In this paper, we show that a policy-constructive program exhibits deterministic concurrency in the sense that all policy-conformant interleavings produce the same input-output behaviour. Policies are conservative and support the csm types existing in current SP languages. This work is a follower of a old work we did in 2009, published at LCTES about scheduling policies.