Predicting timing behavior is key to reliable realtime system design and verification, but becomes increasingly difficult for current multiprocessor systems on chip. The integration of formerly separate functionality into a single multicore system introduces new inter-core timing dependencies, resulting from the common use of the now shared resources. In order to conservatively bound the delay due to the shared resource accesses, upper bounds on the potential amount of conflicting requests from other processors are required. This paper proposes a method that captures the request distances of multiple shared resource accesses by single tasks and also by multiple tasks that are dynamically scheduled on the same processor. Unlike previous work, we acknowledge the fact that on a single processor, tasks will not actually execute in parallel, but in alternation. This consideration leads to a more accurate load model. In a final step, the approach is extended to allow addressing also dynamic cache misses that do not occur at predefined times but surface dynamically during the execution of the tasks.

Abstract-As multiprocessor systems are increasingly used in real-time environments, scheduling and synchronization analysis of these platforms receive growing attention. However, most known schedulability tests lack a general applicability. Common constraints are a periodic or sporadic task activation pattern, with deadlines no larger than the period, or no support for shared resource arbitration, which is frequently required for embedded systems. In this paper, we address these constraints and present a general analysis which allows the calculation of response times for fixed priority task sets with arbitrary activations and deadlines in a partitioned multiprocessor system with shared resources. Furthermore, we derive an improved bound on the blocking time in this setup for the case where the shared resources are protected according to the Multiprocessor Priority Ceiling Protocol (MPCP).