Potential Deadlocks Research Articles

The Discriminating Power of Multiplicities in theλ-Calculus

The λ -calculus with multiplicities is a refinement of the lazy λ -calculus where the argument in an application comes with a multiplicity, which is an upper bound to the number of its uses. This introduces potential deadlocks in the evaluation. We study the discriminating power of this calculus over the usual λ -terms. We prove in particular that the observational equivalence induced by contexts with multiplicities coincides with the equality of Lévy–Longo trees associated with λ -terms. This is a consequence of the characterization we give of the corresponding observational precongruence, as an intensional preorder involving η -expansion, namely, Ong's lazy Plotkin–Scott–Engeler preorder.

Termination, deadlock and divergence in the λ-calculus with multiplicities

The λ-calculus with multiplicities is a refinement of the lazy λ-calculus where the argument in an application comes with a multiplicity, which is an upper bound to the number of its uses. This introduces potential deadlocks in the evaluation. We study various observation scenarios for this calculus, depending on the way we observe termination, deadlock and divergence. We relate these observational semantics with the intensional interpretation of λ-terms, by means of Lévy-Longo trees. We show in particular that the inclusion of such trees coincides with the “flat” observational semantics, where deadlocks and convergence are distinguished.

Scheduling flexible manufacturing systems using Petri nets and heuristic search

Petri net modeling combined with heuristic search provides a new scheduling method for flexible manufacturing systems. The method formulates a scheduling problem with a Petri net model. Then, it generates and searches a partial reachability graph to find an optimal or near optimal feasible schedule in terms of the firing sequence of the transitions of the Petri net model. The method can handle features such as routing flexibility, shared resources, lot sizes and concurrency. By following the generated schedule, potential deadlocks in the Petri net model and the system can be avoided. Hence the analytical overhead to guarantee the liveness of the model and the system is eliminated. Some heuristic functions for efficient search are explored and the experimental results are presented. >

Compressionless routing

Compressionless Routing (GR) is a new adaptive routing framework which provides a unified framework for efficient deadlock-free adaptive routing and fault-tolerance. CR exploits the tight-coupling between wormhole routers for flow control to detect potential deadlock situations and recover from them. Fault-tolerant Compressionless Routing (FCR) extends Compressionless Routing to support end-to-end fault-tolerant delivery. Detailed routing algorithms, implementation complexity and performance simulation results for CR and FCR are presented.CR has the following advantages: deadlock-free adaptive routing in torus networks with no virtual channels, simple router designs, order-preserving message transmission, applicability to a wide variety of network topologies, and elimination of the need for buffer allocation messages. FCR has the following advantages: tolerates transient faults while maintaining data integrity (nonstop fault-tolerance), tolerates permanent faults, can be applied to a wide variety of network topologies, and eliminates the need for software buffering and retry for reliability. These advantages of CR and FCR not only simplify hardware support for adaptive routing and fault-tolerance, they also can simplify communication software layers.

Evaluation of resource allocation policies in a production line using Petri nets

We analyse the flow of workpieces in Petri net models of production lines, depending on different control policies and resource assignments. In particular, we show how an invariant-based algorithm can be used for detecting and avoiding potential deadlocks in the system under consideration while reducing the number of states of its reachability graph. A detailed description of the proposed methodology is given along with a case study whose possible deadlock situations are determined, and all the resource allocation policies, which have to be modified in order to avoid their occurrence, are analysed.

The routing problem in transputer-based parallel systems

The availability of a robust and reliable routing support is of primary importance in transputer-based parallel systems. The difficulties in the design of such a software system lie mainly in the necessity of guaranteeing the absence of communication deadlocks between its component processes. Many techniques have recently been proposed in the literature for solving this problem, but until now they seem to have been rarely used in practical applications. The paper expounds the theory needed for setting up a general-purpose routing support. First, the essential features of a routing system are sketched and the main techniques and solutions available are briefly surveyed, highlighting their advantages and limits of applicability. Then a graphical representation of the program data exchanges, the I/O graph, which makes it possible to detect potential deadlock conditions, is introduced. Its application in the design of a deadlock-free routing system for squared mesh networks is given by way of an example. Finally, some transputer-dependent implementative issues are discussed, showing how to improve the routing support performance.

Deadlock prediction for Escrow transactions

The Escrow transactional method permits long-lived transactions to update records without blocking concurrent access by other transactions to records modified. A situation may occur in an Escrow system in which an update request cannot currently be granted, but if the requesting transaction is allowed to wait, the resulting situation is safe in the sense of the banker's algorithm, i.e. a schedule to grant requests exists whereby all current requests can be granted. Any algorithm to find such a schedule must predict potential deadlocks, and we show that this problem is NP-complete, using a variant of a proof by Gold. The proof draws an analogy between transactional deadlock prediction and the banker's algorithm, and thus is of independent interest. In the conclusions of Section 5 we point out some basic negative performance ramifications of deadlock avoidance/detection inherent in the standard approach of the banker's algorithm; this suggests an avenue for further research.

Managing Deadlocks in Negotiation

An earlier article in this journal outlined a model of the process of negotiation with particular reference to negotiation in the industrial relations context. The model suggests that negotiations go through five phases or patterns of negotiating activity as the negotiators move through to a settlement. On the basis of the model, it is possible to identify several implications for negotiators, and, in particular, to make the point that the two parties must jointly manage their progress through the negotiations. Within the negotiation process there are three potential deadlocks which could emerge to obstruct this progress if the negotiations were not properly and jointly managed. This article develops the concept of deadlocks in negotiation more fully, and attempts to identify the implications for negotiators by suggesting how deadlocks might be identified and overcome.

A linear-history semantics for languages for distributed programming

A denotational semantics is given for a language for distributed programming based on communication (CSP). The semantics uses both linear sequences of communications to record computations and special states, called ‘expectation sets’, characterizing potential deadlocks. For any well-formed program segment the semantics is a relation between attainable states and the communication sequences needed to attain these states. In binding two or more processes we match and merge the communication sequences assumed by each process to obtain a sequence and state of the combined process. The approach taken here is distinguished by relatively simple semantic domains and ordering.

A DAG-Based Algorithm for Prevention of Store-and-Forward Deadlock in Packet Networks

Store-and-forward deadlock (SFD) occurs in packet- switched computer networks when, among some cycle of packets buffered by the communication system, each packet in the cycle waits for the use of the buffer currently occupied by the next packet in the cycle. Several techniques for the prevention of SFD are known, but all exact some cost in terms of efficient and flexible packet handling. An ideal SFD-prevention technique is as unobtrusive as possible; it imposes no routing restrictions on packets, does not require that the buffer pool on each node grow with network size, and imposes no buffer-pool partitioning. All SFD-prevention techniques described so far lack some or all of these desirable properties. The new algorithm here described has all of them; in return, it imposes other unconventional costs. Under certain circumstances it requires that packets be rerouted around areas of potential deadlock, and one arbitrarily chosen node is required to accept within finite time any packet seeking entrance to its buffer pool, even if this requires erasing some packet. It is argued nonetheless that these costs are imposed infrequently enough and are sufficiently well manageable by heuristic techniques to make this new algorithm an attractive and practical alternative to the older techniques. An implementation designed for a microprocessor network now under construction is described.

Prevention of Deadlocks in Packet-Switched Data Transport Systems

This paper first Surveys a number of potential deadlocks inherent in store-and-forward networks and outlines corresponding countermeasures. It then goes on to a more detailed treatment of the most important deadlock types. Finally, necessary and sufficient conditions are given and proven for the use of process ordering and generalized resource ordering techniques to avoid deadlocks in arbitrary systems of interacting processes.