Composable, nestable, pessimistic atomic statements

Abstract

In this paper we introduce a new method for pessimistically implementing composable, nestable atomic statements. Our mechanism, called shelters, is inspired by the synchronization strategy used in the Jade programming language. Unlike previous lock-based pessimistic approaches, our mechanism does not require a whole-program analysis that computes a global lock order. Further, this mechanism frees us to implement several optimizations, impossible with automatically inserted locks, that are necessary for scaling on recent multi-core systems. Additionally we show how our basic mechanism can be extended to support both open- and closed-nesting of atomic statements, something that, to our knowledge, has not yet been implemented fully-pessimistically in this context. Unlike optimistic, transactional-memory-based approaches, programmers using our mechanism do not have to write compensating actions for open-nesting, or worry about the possibly awkward semantics and performance impact of aborted transactions.