Thread Allocation Protocols for Distributed Real-time and Embedded Systems

Abstract. We study the problem of thread allocation in asynchronous distributed real-time and embedded systems. Each distributed node handles a limited set of resources, in particular a limited thread pool. Different methods can be invoked concurrently in each node, either by external agents or as a remote call during the execution of a method. In this paper we study thread allocation under a WaitOnConnection strategy, in which each nested upcall made while a thread is waiting must be made in a different thread. We study protocols that control the allocation of threads to guarantee the absence of deadlocks. First, we introduce a computational model in which we formally describe the different protocols and their desired properties. Then, we study two scenarios: a single agent performing sequential calls, and multiple agents with unrestricted concurrency. For each scenario we present (1) algorithms to compute the minimum amount of resources to avoid deadlocks, and (2) run-time protocols that control the allocation of these resources.

Adaptive and Transparent Data Distribution Support for Synchronous Groupware

The datao f agro6 ware applicatio must be shared to suppo rt interactiok betweenconw: o rating users. There have been a lo o discussioJ abo ut the best distributio scheme fo the datao f agrokD ware applicatio-- Many existinggrot ware platfo:w otf suppop o ne distributio scheme, e.g. a replicatedo a central scheme. The selected scheme appliesto the entire applicatiok In owo piniok nok o f these architectures fits wellfo every gro ware applicatioL In this paper we describe a develo:L2 t platfok that allo ws a develo er to determine the distributio scheme fo each shared datao ject. With the helpo an o ject-ow]k ted pro2:Dw]kN principle it also achieves a maximum o transparencyfo the applicatio develo er

Distributed priority inheritance for real-time and embedded systems

Abstract. We study the problem of priority inversion in distributed real-time and embedded systems and propose a solution based on a distributed version of the priority inheritance protocol (PIP). Previous approaches to priority inversions in distributed systems use variations of the priority ceiling protocol (PCP), originally designed for centralized systems as a modification of PIP that also prevents deadlock. PCP, however, requires maintaining a global view of the acquired resources, which in distributed systems leads to high communication overhead. This paper presents a distributed PIP built on top of a deadlock avoidance schema that requires much less communication than PCP. Since the system is already deadlock free and priority inversions can be detected locally, we obtain an efficient dynamic resource allocation system that prevents deadlocks and handles priority inversions