Graph-Based Optimizations for Multiprocessor Nested Resource Sharing

Multiprocessor resource synchronization and locking protocols are of great importance to utilize the computation power of multiprocessor real-time systems. Hence, in the past decades a large number of protocols have been developed and analyzed. The recently proposed dependency graph approach has significantly improved the schedulability for frame-based and periodic real-time task systems. However, the dependency graph approach only supports non-nested resource access, i.e., each critical section can only access one shared resource. In this paper, we develop a dependency graph based protocol that allows nested resource access, where a critical section can access multiple shared resources at the same time. First, constraint programming is applied to construct a dependency graph that determines the execution order of critical sections. Afterwards, a schedule is generated based on this order. To show the feasibility of our proposed protocol, we provide extensive numerical evaluations under different configurations. The evaluation results show that our approach has very good performance with respect to schedulability for frame-based and periodic realtime task systems, whereas the existing results applicable for sporadic task systems have worse performance under such a limited setting.