Intervals are a higher-level thread primitive that replaces threads, signals, and barriers. They are under active development at ETH Zurich as part of the PhD research of Nicholas Matsakis.
The goal of intervals is to provide a flexible, high-level primitive for writing parallel programs. Specifying parallel tasks and their interdependencies using intervals is simplified. Dynamic checks help to detect deadlocks and other errors before they happen.
The intervals system is available as a Java library, though versions for other languages are also available.
The intervals library is also the basis of the Harmonic programming language. The Harmonic compiler statically guarantees data-race freedom. The Harmonic language itself compiles to the JVM and can fully inter-operate with Java and other JVM-based languages.