Debugging Scheme Fair Threads

There are two main policies for scheduling thread-based concurrent programs: preemptive scheduling and cooperative scheduling. The former is known to be difficult to debug, because it is usually non-deterministic and can lead to data races or difficult thread synchronization. We believe the latter is a better model when it comes to debugging programs. In this paper, we discuss the debugging of Scheme Fair Threads, that are based on cooperative scheduling and synchronous reactive programming. In this approach, thread communication and synchronization is achieved by means of special primitives called signals, which ease the debugging process. We present the tools we have implemented to deal with the main types of concurrent bugs that can arise in this special programming framework