Analyzing Permission Transfer Channels for Dynamically Typed Languages

Abstract : Communicating Sequential Process (CSP) is nowadays a popular concurrency model in which threads/processes communicate by exchanging data through channels. Channels help in orchestrating concurrent processes but do not solve perse data races. To prevent data races in the channel model, many programming languages rely on type systems to express ownership and behavioural restrictions such as immutability. However, dynamically-typed languages require run-time mechanisms because of the lack of type information at compile-time. In this paper, we propose to augment channels with four different permission transfer semantics. We explore two mechanisms to implement such permission transfers at run time: write barriers and partial-read barriers. To validate our approach we implemented a channel framework in Pharo, and we extended it with different permission transfer semantics. We report on performance measurements of both (a) the transfer overhead on a single object and on a graph of objects, and (b) the per-object access overhead incurred by ownership checks. This work stands as a cornerstone of future work on adaptive optimizations for permission transfer channels.