Although the typical process-layout manufacturing environment is susceptible to deadlocks, the problem of deadlock resolution in this context has only lately been undertaken by the scientific community. Previous studies have found that deadlock avoidance methodologies seem to be the most appropriate for this particular context. Unfortunately, in the general case, these methods suffer from high computational complexity which results in heuristic solutions and/or reduced performance. Taking the position that any solution to the problem should be scalable and provably correct, this paper proposes an analytical framework for designing deadlock avoidance policies for a subclass of Resource Allocation Systems (RAS). Specifically, this subclass is characterized by the fact that jobs in the system are defined by deterministic job-step sequences with every step in the sequence requiring a single unit of the system resources. Job-step models are appropriate for the study of the deadlo...

Deadlock is an increasingly pressing concern as the multicore revolution forces parallel programming upon the average programmer. Existing approaches to deadlock impose onerous burdens on developers, entail high runtime performance overheads, or offer no help for unmodified legacy code. Gadara automates dynamic deadlock avoidance for conventional multithreaded programs. It employs whole-program static analysis to model programs, and Discrete Control Theory to synthesize lightweight, decentralized, highly concurrent logic that controls them at runtime. Gadara is safe, and can be applied to legacy code with modest programmer effort. Gadara is efficient because it performs expensive deadlock-avoidance computations offline rather than online. We have implemented Gadara for C/Pthreads programs. In benchmark tests, Gadara successfully avoids injected deadlock faults, imposes negligible to modest performance overheads (at most 18%), and outperforms a software transactional memory system. Tests on a real application show that Gadara identifies and avoids both previously known and unknown deadlocks while adding performance overheads ranging from negligible to 10%. 1

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Currently, conflict-free routing in AGV systems is established by means of one of the following three approaches: (i) the problem elimination through the adoption of a segmented path flow or tandem queue configuration, (ii) the identification of imminent collisions through forward sensing and their aversion through vehicle backtracking and/or rerouting, or (iii) the imposition of zone control and extensive route pre-planning, typically based on deterministic timing of the vehicle traveling and docking stages. Among these three approaches, the segmented path flow-based approach presents the highest robustness to the system stochasticities/randomness, but at the cost of restricted vehicle routings and the need for complicated handling operations. This paper proposes an alternative conflict resolution strategy that will ensure robust AGV conflict resolution, while maintaining the operational flexibility provided by free vehicle travel on arbitrarily structured guidepath networks. Specific...

The development of efficient deadlock avoidance policies (DAP's) for sequential resource allocation systems (RAS) is a problem of increasing interest in the scientific community, largely because of its relevance to the design of large-scale flexibly automated manufacturing systems. Much of the work on this problem existing in the literature, is focused on the so called Single-Unit RAS model, which is the simplest model in the considered class of RAS. Furthermore, due to a well-established result stating that, even for single-unit RAS, the computation of the maximally permissive DAP is computationally intractable (NP-hard), many researchers (including our group) have focused on obtaining good suboptimal policies which are computationally tractable (scalable) and provably correct. In the first part of the paper, it is shown, however, that for a large subset (in fact, a majority) of single-unit RAS, the optimal DAP can be obtained in real-time with a computational cost which is ...

Overwhelmed by the complexity of the FMS Deadlock Avoidance problem, current research has, for the most part, ignored the aspects (and benefits) related to flexible (dynamic) job routing. Extending current structural control policies, based on static job routing, to accommodate routing flexibility is nontrivial, primarily due to the fact that the possible routing options for a single job can grow exponentially fast. Hence, computationally efficient techniques are required to incorporate the inherent FMS routing flexibility to current structural control schemes. This paper undertakes the investigation of the problem of integrating routing flexibility in FMS structural control, by addressing the problem of "optimal" job re-routing in case of operational contingencies. Analytical formulations and efficient solution algorithms are developed for the case that the FMS is structurally controlled by a class of recently emerging polynomial-complexity, one-step lookahead deadlock avoid...

Current strategic and technological trends in discrete-part manufacturing require extensive and #exible automation of the underlying production systems. However, even though a great deal of work has been done to facilitate manufacturing automation at the hardware component level, currently there is no adequately developed control methodology for these environments.

Liveness-enforcing supervision of sequential resource allocation systems is currently a well-defined problem, underlying the operation of many contemporary technological systems, spanning a wide spectrum of applications. This technical note provides a brief overview of the currently available results, delineating, both, our major analytical understandings/characterizations concerning the problem concepts/structure and its complexity, and also, our ability to synthesize effective and computationally tractable solutions to it. The last part of the document identifies open / unaddressed research issues, the resolution of which will extent the power of the current theory and will allow the integration of the developed results in the broader control frameworks managing the behavior of these environments.

Abstract — Ensuring deadlock-free execution of concurrent programs is a notoriously difficult problem, but an increasingly important one as multicore processors compel performanceconscious software developers to parallelize applications. We propose and validate a novel methodology for dynamically controlling the execution of concurrent software in order to provably avoid deadlocks. The methodology is based on supervisory control of discrete event systems modeled by Petri nets. Specifically, we synthesize feedback controllers for concurrent programs based on the theory of supervision based on place invariants and implement the controllers online to guarantee deadlock avoidance. We describe a full implementation of this methodology and report initial experimental results demonstrating its effectiveness and scalability. I.

Abstract. This paper studies the problem of resource availability in the context of mobile code for embedded systems such as smart cards. It presents an architecture dedicated to controlling the usage of a single resource in a multi-process operating system. Its specificity lies in its ability to improve the task scheduling in order to spare resources. Our architecture comprises two parts. The first statically computes the resource needs using a dedicated lattice. The second guarantees at runtime that there will always be enough resources for every application to terminate, thanks to an efficient deadlock-avoidance algorithm. The example studied here is an implementation on a JVM (Java Virtual Machine) for smart cards, dealing with a realistic subset of the Java bytecode. 1