Relativistic Programming in Haskell Using Types to Enforce a Critical Section Discipline

Relativistic programming (RP) is a concurrent programming model in which readers can safely access shared data concurrently with writers that are modifying it. RP has been used extensively in operating system kernels, most notably in Linux, and is widely credited with improving the performance and scalability of Linux on highly concurrent architectures. However, using RP primitives safely is tricky, and existing implementations of RP do not identify most unsafe uses statically. This work introduces Monadic RP, a GHC Haskell library for RP, and presents an example of its use. To our knowledge, Monadic RP is the first RP implementation in Haskell. It provides a novel mechanism to statically rule out a subset of unsafe relativistic programs by using types to separate readside and write-side critical sections, and to restrict the operations available in each. This work describes the current status of our implementation, presents a brief experimental evaluation of it, and discusses directions for ongoing and future work.