Supporting Nested Locking in Multiprocessor Real-Time Systems

This paper presents the first real-time multiprocessor locking protocol that supports fine-grained nested resource requests. This locking protocol relies on a novel technique for ordering the satisfaction of resource requests to ensure a bounded duration of priority inversions for nested requests. This technique can be applied on partitioned, clustered, and globally scheduled systems in which waiting is realized by either spinning or suspending. Furthermore, this technique can be used to construct fine-grained nested locking protocols that are efficient under spin-based, suspension-oblivious or suspension-aware analysis of priority inversions. Locking protocols built upon this technique perform no worse than coarse-grained locking mechanisms, while allowing for increased parallelism in the average case (and, depending upon the task set, better worst-case performance).