Abstmct-A direct application of commonly used synchronization primitives such as semaphores, monitors, or the Ada rendezvous can lead to uncontrolled priority inversion, a situation in which a higher priority job is blocked by lower priority jobs for an indefinite period of time. In this paper, we investigate two protocols belonging to the class of priority inheritance protocols, called the basic priority inheritance protocol and the priority ceiling protoool. We show that both protocols solve this uncontrolled priority inversion problem. In particular, the priority ceiling protocol reduces the worst case task blocking time to at most the duration of execution of a single critical section of a lower priority task. In addition, this protocol prevents the formation of deadlocks. We also derive a set of sufficient conditions under which a set of periodic tasks using this protocol is schedulable.

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Abstract-In this paper, we present a Minimum Spanning Tree (MST) based topology control algorithm, called Local Minimum Spanning Tree (LMST), for wireless multi-hop networks. In this algorithm, each node builds its local minimum spanning tree independently and only keeps on-tree nodes that are one-hop away as its neighbors in the final topology. We analytically prove several important properties of LMST: (1) the topology derived under LMST preserves the network connectivity; (2) the node degree of any node in the resulting topology is bounded by 6; and (3) the topology can be transformed into one with bi-directional links (without impairing the network connectivity) after removal of all uni-directional links. These results are corroborated in the simulation study.

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