Multiversion Integrated Concurrency Control for Hard Real-time Systems

We describe an integrated multi-version concurrency control protocol for hard real-time systems. The new protocol is based on a combination of protocols originally developed for database systems, but is extended to permit predictable low-overhead implementation with analytical guarantees of worst-case blocking when used with rate-monotonic scheduling. A useful property of the protocol is that long queries do not block short update tasks. The speciic contributions of the paper include formalizing a common implementation strategy (buuering) in a way that facilitates reasoning about correctness and schedulability. More generally, it illustrates an approach to adapting concurrency control protocols to hard-real-time systems by using semantic information (task rates and access patterns, in this case) that is typically available to real-time system designers.