Ada 2012

Abstract

As from Ada 2005, the language has supported different dispatching policies including fixed priority (FP) and earliestdeadline first (EDF). EDF dispatching can be applied across the whole range of priorities or across a restricted range. In this way, EDF scheduling is integrated into a FP framework. Baker's Stack Resource Policy (SRP) is also integrated with Ada's immediate priority ceiling protocol to support resource sharing using protected objects. However, with the introduction of support for global, partitioned and cluster scheduling for multiprocessor systems, the use of protected objects in applications needs to be re-evaluated. This is because Ada does not completely define how protected objects are accessed in a multiprocessor environment and because the SRP cannot be directly applied to multiprocessors. This paper reviews the currently available multiprocessor resource allocation policies and analyzes their applicability to Ada. It proposes some new Ada mechanisms that would facilitate the programming of a variety of protected object access protocols.