A Schedulability Compatible Multiprocessor Resource Sharing Protocol -- MrsP

Abstract

Lock-based resource sharing protocols for single processor systems are well understood and supported in programming languages and in Real-Time Operating Systems. In contrast, multiprocessor resource sharing protocols are less well developed with no agreed best practice. In this paper we propose a new multiprocessor variant of a protocol based on the single processor priority ceiling protocol. The distinctive nature of the new protocol is that tasks waiting to gain access to a resource must service the resource on behalf of other tasks that are waiting for the same resource (but have been preempted). The form of the protocol is motivated by the desire to link the protocol with effective schedulability analysis. The protocol is general purpose, but is developed in this paper for partitioned fixed priority systems with the sporadic task model. Two methods of supporting the protocol are described, as is a prototype `proof of concept' implementation for one of these schemes.