Turning Krieger’s MCS Lock into a Send Queue or, a Case for Reusing Clever, Mostly Lock-Free Code in a Different Area

Lockand wait-free data structures can be constructed in a generic way. However, when complex operations are involved, their practical use is rather limited due to high performance overheads and, in some settings, difficult to fulfil object lifecycles. While working on a synchronous inter-processor communication (IPC) path for multicore systems, we stumbled over a clever piece of code that did fulfil most of the properties that this path requires for its send queue. Unfortunately, this piece of code was by no means a data-structure publication or somehow related to send queues. Reporting on our experience in translating Krieger’s MCS-style reader-writer lock into a send queue for cross-processor IPC, we would like to make the point that sometimes, searching for code could end up in a valuable treasure chest even for largely different areas.