Constant-RMR Abortable Reader-Priority Reader-Writer Algorithm

The concurrent reader-writer problem (Courtois, 1971) involves two classes of processes: readers and writers, both of which wish to access a shared resource. Many readers can access the shared resource at the same time. However, if a writer is accessing the resource, no readers or other writers can access the resource at the same time. In the reader-priority version of the problem, readers are prioritized over writers when processes from both classes are trying to access the shared resource. Previous research (Bhatt, 2010) showed a reader-priority constant-RMR multi-reader, multi-writer algorithm for Cache-Coherent (CC) systems. However, this algorithm does not allow for readers or writers to abort, which allows readers and writers waiting for the resource to stop trying to access the resource and to quickly return to the Remainder Section of the code, where the process performs tasks unrelated to the shared resource. This thesis presents an abortable constant-RMR reader-priority multi-reader single-writer algorithm for CC systems. Additionally, we show how to generalize the algorithm into a multi-reader multi-writer algorithm using any given abortable mutual exclusion algorithm. The algorithm is proven rigorously by invariants and tested using a system of mathematical specification and model-checking tools (PlusCal/TLA+/TLC)