Extensible Scheduling in a Haskell-based Operating System

This thesis presents Lighthouse, an experimental branch of the Haskell-based House operating system which integrates Li et al.\u27s Lightweight Concurrency framework. First and foremost, it improves House\u27s viability as a real operating system by providing a new extensible scheduler framework which makes it easy to experiment with different scheduling policies. In particular, Lighthouse extends Concurrent Haskell with thread priority and implements a priority-based scheduler which significantly improves system responsiveness when compared with GHC\u27s normal round-robin scheduler. Even while doing this, it improves on House\u27s claim of being written in Haskell by moving a whole subsystem out of the complex C-based runtime system and into Haskell itself. In addition, Lighthouse also includes an alternate, simpler implementation of Lightweight Concurrency which takes advantage of House\u27s unique setting (running directly on uniprocessor x86 hardware). This experience sheds light on areas that need further attention before the system can truly be viable---primarily interactions between blackholing and interrupt handling. In particular, this thesis uncovers a potential case of self-deadlock and suggests potential solutions. Finally, this work offers further insight into the viability of using high-level languages such as Haskell for systems programming. Although laziness and blackholing present unique problems, many parts of the system are still much easier to express in Haskell than traditional languages such as C