Classical Mutual Exclusion Problem Research Articles

Group mutual exclusion in linear time and space

We present two algorithms for the Group Mutual Exclusion (GME) Problem that satisfy the properties of Mutual Exclusion, Starvation Freedom, Bounded Exit, Concurrent Entry and First Come First Served. Both our algorithms use only simple read and write instructions, have O(N) Shared Space complexity and O(N) Remote Memory Reference (RMR) complexity in the Cache Coherency (CC) model. Our first algorithm is developed by generalizing the well-known Lamport's Bakery Algorithm for the classical mutual exclusion problem, while preserving its simplicity and elegance. However, it uses unbounded shared registers. Our second algorithm uses only bounded registers and is developed by generalizing Taubenfeld's Black and White Bakery Algorithm to solve the classical mutual exclusion problem using only bounded shared registers. We show that contrary to common perception our algorithms are the first to achieve these properties with this combination of complexities.

Randomized mutual exclusion on a multiple access channel

In this paper we consider the mutual exclusion problem on a multiple access channel. Mutual exclusion is one of the fundamental problems in distributed computing. In the classic version of this problem, n processes execute a concurrent program that occasionally triggers some of them to use shared resources, such as memory, communication channel, device, etc. The goal is to design a distributed algorithm to control entries and exits to/from the shared resource (also called a critical section), in such a way that at any time, there is at most one process accessing it. In our considerations, the shared resource is the shared communication channel itself (multiple access channel), and the main challenge arises because the channel is also the only mean of communication between these processes. We consider both the classic and a slightly weaker version of mutual exclusion, called $$\varepsilon $$?-mutual-exclusion, where for each period of a process staying in the critical section the probability that there is some other process in the critical section is at most $$\varepsilon $$?. We show that there are channel settings, where the classic mutual exclusion is not feasible even for randomized algorithms, while the $$\varepsilon $$?-mutual-exclusion is. In more relaxed channel settings, we prove an exponential gap between the makespan complexity of the classic mutual exclusion problem and its weaker $$\varepsilon $$?-exclusion version. We also show how to guarantee fairness of mutual exclusion algorithms, i.e., that each process that wants to enter the critical section will eventually succeed.

Distributed Mutual Exclusion Algorithms for Intersection Traffic Control

Traffic control at intersections is a key issue and hot research topic in intelligent transportation systems. Existing approaches, including traffic light scheduling and trajectory maneuver, are either inaccurate and inflexible or complicated and costly. More importantly, due to the dynamics of traffic, it is really difficult to obtain the optimal solution in a real-time way. Inspired by the emergence of vehicular ad hoc network, we propose a novel approach to traffic control at intersections. Via vehicle to vehicle or vehicle to infrastructure communications, vehicles can compete for the privilege of passing the intersection, i.e., traffic is controlled via coordination among vehicles. Such an approach is flexible and efficient. To realize the coordination among vehicles, we first model the problem as a new variant of the classic mutual exclusion problem, and then design algorithms to solve new problem. Both centralized and distributed algorithms are. We conduct extensive simulations to evaluate the performance of our proposed algorithms. The results show that, our approach is efficient and outperforms a reference algorithm based on optimal traffic light scheduling. Moreover, our approach does not rely on traffic light or intersection controller facilities, which makes it flexible and applicable to various kinds of intersections.

PBCBT: An Improvement of NTBCBT Algorithm

The classic mutual exclusion problem in distributed systems occurs when only one process shouldaccess a shared resource. Various algorithms are proposed in order to solve this problem. When using a permission based approach which consist in exchanging permission messages togrant access to the critical resource, less messages should be sent over the network because bandwi dth consumption and synchronization delay should be reduced. Richa, shikha and Pooja proposedan algorithm using nodes logically organized in a complete binary tree. This algorithmcalled NTBCBT requires 4log2(N) messages per access to critical section and a synchronization delay of 3log2(N) for a set of N nodes competing for the critical ressource.In this paper, we study NTBCBT and we show that this algorithm has proble ms related with safety, liveness and scheduling. We improve this algorithm by correcting these weaknesses. Moreover, our algorithm requires 3log(N) messages per access to critical section and a s