Deadlock Model Research Articles

Deadlock resolution in wait-for graphs by vertex/arc deletion

A deadlock occurs in a distributed computation if a group of processes wait indefinitely for resources from each other. In this paper we study actions to be taken after deadlock detection, especially the action of searching for a small deadlock-resolution set. More precisely, given a “snapshot” graph G representing a deadlocked state of a distributed computation governed by a certain deadlock model $${\mathbb {M}}$$ , we investigate the complexity of vertex/arc deletion problems that aim at finding minimum vertex/arc subsets whose removal turns G into a deadlock-free graph (according to model $${\mathbb {M}}$$ ). Our contributions include polynomial-time algorithms and hardness proofs, for general graphs and for special graph classes. Among other results, we show that the arc deletion problem in the OR model can be solved in polynomial time, and the vertex deletion problem in the OR model remains NP-complete even for graphs with maximum degree $${\varDelta }(G) = 4$$ , but is solvable in $$O (m \sqrt{n})$$ time for graphs with $${\varDelta }(G)\le 3$$ .

Implementing a Score-Time based Model for Handling Deadlocks in Football Group Matches

In a typical football event, three possibilities can occur: a winner, a loser/runners-up, or a tie. The latter however is not left in that status especially when it has to do with a group or league game; as a resolve is needed to establish two partitions – winner and loser. Different deadlock models are employed to resolve different deadlock scenarios. Football histories and events have however shown that most models failed to solve some complex deadlocks. Tossing of coin is a particular kind of model that starts where others stopped. Taking the last Africa Cup of Nations (AFCON) 2015 Football Fiesta as a case study however, the use of the ‘last man standing’ deadlock model – coin tossing, proved unpleasant to both teams in questions and generated lots of heat from football fans of both countries. Football at this age has indeed proved in so many ways to be technological-oriented. Bringing manual ‘decision system’ into a game of this century and magnitude prompted the researcher to present an ideal and implementable model that resolves deadlock situations in football group matches. Keyword Football, deadlock, model, coin tossing, AFCON, game, group matches

A deadlock model for a multi-service medium access protocol employing multi-slot N -ary stack algorithm (msSTART)

Many modern multi‐service medium access protocols (MACs) use a collision based capacity request signaling channel as part of a hybrid TDMA frame structure. Multi‐slot Stack Random Access Algorithm (msSTART) is proposed for use in IEEE 802.14 hybrid fiber/coaxial network and will be highly relevant for the S‐MAC development of evolving WATM MAC specifications. This paper studies the performance of msSTART as an example of a Q‐ary tree contention resolution algorithm (CRA) in the wireless environment using the novel Basic Deadlock model. We contrast approximate results for msSTART performance obtained by simulation under extreme inter‐station correlation with analytical results for the more popular p‐persistence CRA used in several testbed WATM implementations. Using three signaling channel schemes designed to provide support for increased system stability, to implement priority in the wireless MAC, and maximise efficiency, we provide comparative results for evaluation of msSTART and p‐persistence ALOHA under what the IEEE 802.14 working group has termed the “disaster scenario”. We find that of the three schemes evaluated the full Contention Mini‐Slot (CMS) sharing scheme employing multiple CMSs per data region extends the protocol's useable load region the furthest. We conclude that Q‐ary tree contention resolution algorithms (in particular msSTART) are best adapted to the wireless environment, providing less case sensitive performance.

Deadlock Models and a General Algorithm for Distributed Deadlock Detection

This paper deals with the problem of deadlock detection in asynchronous message passing systems in a system model that covers unspecified receptions and non-FIFO channels. It presents a hierarchy of deadlock models and deadlock detection problems. It abstracts deadlocks by a general deadlock model that has the same modeling power as the OR-AND model; however, it has much concise expressive power. An abstract general definition of deadlocks in distributed systems is presented that defines deadlocks independently of the underlying deadlock model. This formulation can be used to design a single distributed deadlock detection algorithm which uniformly addresses all deadlocks in the context of various request models such as AND, OR, AND-OR, and k-out-of-n requests. A simple generalized deadlock detection algorithm that uses a circulating token is presented to illustrate the concept. The algorithm is formally described and proven correct. Moreover, possible refinements of the basic solution concerning improvements of token routing and parallel implementation are outlined and evaluated. Extensions to individual and global termination issues are also addressed. Since the proposed deadlock detection algorithm is designed around the abstract definition of deadlocks, it has some very favorable features.

A Two-Level Distributed Detection Algorithm of AND/OR Deadlocks

Numerous algorithms on distributed deadlock detection in distributed systems have been proposed for various deadlock models such as the AND model, OR model, and AND/OR model. This paper describes a new distributed algorithm for the AND/OR model by two levels of deadlock detection procedures. In every deadlock model, the existence of a cycle in a wait-for graph is a necessary condition. At the first level of our algorithm, a wait-for cycle is detected with a very simple operation. If no cycle is found, a deadlock does not exist. In this level, deadlocks consisting of AND-requested nodes are detected, and for the cycle of AND- and OR-requested nodes, an initiator is elected and the second-level algorithm is initiated by the initiator. The second-level algorithm uses the deadlock detection method of Herman and Chandy, but the communication cost is reduced even in the worst case because the second-level operation can be initiated by only qualified initiators.