Real-Time Systems Journal manuscript No. (will be inserted by the editor) Analysis and Implementation of the Multiprocessor BandWidth Inheritance Protocol

Abstract The Multiprocessor Bandwidth Inheritance (M-BWI) protocol is an ex-tension of the Bandwidth Inheritance (BWI) protocol for symmetric multiprocessor systems. Similar to Priority Inheritance, M-BWI lets a task that has locked a resource execute in the resource reservations of the blocked tasks, thus reducing their blocking time. The protocol is particularly suitable for open systems where different kinds of tasks dynamically arrive and leave, because it guarantees temporal isolation among independent subsets of tasks without requiring any information on their temporal pa-rameters. Additionally, if the temporal parameters of the interacting tasks are known, it is possible to compute an upper bound to the interference suffered by a task due to other interacting tasks. Thus, it is possible to provide timing guarantees for a sub-set of interacting hard real-time tasks. Finally, the M-BWI protocol is neutral to the underlying scheduling policy: it can be implemented in global, clustered and semi-partitioned scheduling. After introducing the M-BWI protocol, in this paper we formally prove its iso-lation properties, and propose an algorithm to compute an upper bound to the in-terference suffered by a task. Then, we describe our implementation of the protocol for the LITMUSRT real-time testbed, and measure its overhead. Finally, we com