一种基于移动Agent技术的分布式死锁检测算法

死锁的处理长期以来一直是分布式系统的研究重点,已有许多成熟算法.随着网络技术的发展,越来越多的客户和资源可在网络中自由移动,这种可移动性使得传统算法面临了新的挑战.在这种新的应用背景下,本文结合移动Agent技术,提出了一种分布式系统死锁检测和解除算法：Agent Guard.该算法使用一个移动Agent,使其遵循一定的路线算法在各个站点间移动来收集资源请求和分配信息并进行分析,从而发现并解除死锁.模拟实验证明,A-gent Guard算法能取得较短的死锁持续时间,较小的伪死锁率,且网络的通信复杂度也有降低.     

MPI同步通信顺序模型死锁静态检测算法

静态检测MPI程序同步通信死锁比较困难,通常需要建立程序模型。顺序模型是其他所有复杂模型的基础。通过一种映射方法将顺序模型转化为字符串集合,将死锁检测问题转化为等价的多队列字符串匹配问题,从而设计并实现了一种MPI同步通信顺序模型的静态死锁检测算法。该算法的性能优于通常的环检测方法,并能适应动态消息流。     

基于动态探针的分布式死锁预防策略

数据库系统中事务死锁的检测和预防,对提高系统并发性和整体性能具有重要意义。在研究了现有的分布式数据库系统死锁预防策略的基础上,利用创建动态探针(DP)技术,提出了一种改进的死锁预防策略。该DP方法在创建探针后将其发往可能产生死锁的节点,接收到探针后,根据节点信息与探针所包含信息的比较结果,可以判断是否有死锁发生,从而达到预防死锁的目的。分析表明,该方法提高了死锁预防的有效性和系统资源的利用率。     

对于避免死锁的安全算法的改进

在每种资源只有一个个体的情况下,本文给出了一种避免死锁的安全算法。该算法是对现有的一种安全算法的改进,改进后的算法被命名为触网式安全算法。该算法把以前算法的运算级次从n2(n表示系统中进程的数目）降低为n,从而大大地节省了检测开销。     

谈操作系统中的死锁问题

进程死锁问题是操作系统的主要问题之一,很多学者专家一直在研究怎样解决这个问题.本文针对操作系统中经常出现的死锁问题进行了讨论,阐述了死锁出现的原因、四个必要条件,以及死锁的处理方法,最后谈论了一个避免死锁的经典算法--银行家算法.     

移动Agent系统的一种分布式死锁检测方案

传统的分布式死锁解决方案不适合于实体在网络中自由移动的MAS系统.本文描述了一种移动Agent系统的分布式死锁算法,使用专职Agent从事死锁检测和解决.该方案的特点是地点参考、拓扑独立、容错、异步操作.文中建立了StochasticPetri Net模型,并使用仿真试验给出它和Diffusion Computation算法的性能比较.     

基于Petri网并行程序通信死锁的检测和预防

无死锁是并行程序正确性的主要条件之一,已有研究成果关注于死锁检测,但对死锁预防研究较少。该文在对消息传递模式并行程序各种通信过程进行分类介绍的基础上,借助Petri网进行建模,提出程序死锁与Petri网死标识的对应关系,给出通信死锁检测算法,进而针对2种引起通信死锁的原因提出了3种预防方法,通过比较提出最佳方案。该方法既有较好的通用性,又可用于并行算法设计阶段的死锁预防以提高并行编程效率。     

星形图上最小无死锁受限条件及无死锁路径算法

针对是形图中台能产生死锁的问题，对星形图上无无线锁的路径算法进行了研究，得到了星形图上的两类最小无死锁受限条件，并给出了一个满足该两类最小无死锁受限条件的无死锁路径算法。同时还证明了文献中提出的两个死锁受限条件分别只是该文所提出的两类最小无死锁受限条件的一个特例。     

N个有限状态机的死锁和死环回避算法

死锁和死环是分布式系统或计算机网络中进程间通信时经常发生的逻辑错误，它们往往造成分布式系统中的部分主机或整个系统瘫痪，本文提出两个回避死锁和死环的算法，这些算法可被用来设计分布式系统的通信协议，从而提高分布式系统的可靠性和减少协议开发成本。     

基于SUIF2的静态死锁检测方法研究

死锁是并发程序中常见的错误之一,且由于并发程序运行的不确定性使得死锁难以检测。针对该问题,通过对C多线程程序死锁的分析,提出了一种基于SUIF2的静态死锁检测方法,设计了基于SUIF2的C多线程程序静态死锁检测的框架结构和锁集分析算法。最后通过一个实例说明了该检测方法的有效性。     

False Deadlock Detection in Distributed Systems

Detecting a nonexistent deadlock in distributed systems has been referred to as false deadlock detection. This correspondence shows that false deadlock wi1l never occur in a system of two-phase locking transactions. We also describe an algorithm to avoid false deadlock detection when transactions are not two-phase locking.     

Deadlock detection in distributed database systems: a new algorithm and a comparative performance analysis

This paper attempts a comprehensive study of deadlock detection in distributed database systems. First, the two predominant deadlock models in these systems and the four different distributed deadlock detection approaches are discussed. Afterwards, a new deadlock detection algorithm is presented. The algorithm is based on dynamically creating deadlock detection agents (DDAs), each being responsible for detecting deadlocks in one connected component of the global wait-for-graph (WFG). The DDA scheme is a “self-tuning” system: after an initial warm-up phase, dedicated DDAs will be formed for “centers of locality”, i.e., parts of the system where many conflicts occur. A dynamic shift in locality of the distributed system will be responded to by automatically creating new DDAs while the obsolete ones terminate. In this paper, we also compare the most competitive representative of each class of algorithms suitable for distributed database systems based on a simulation model, and point out their relative strengths and weaknesses. The extensive experiments we carried out indicate that our newly proposed deadlock detection algorithm outperforms the other algorithms in the vast majority of configurations and workloads and, in contrast to all other algorithms, is very robust with respect to differing load and access profiles. Received December 4, 1997 / Accepted February 2, 1999     

Deadlock detection in distributed systems

The author describes a series of deadlock detection techniques based on centralized, hierarchical, and distributed control organizations. The point of view is that of practical implications. An up-to-date and comprehensive survey of deadlock detection algorithms is presented, their merits and drawbacks are discussed, and their performances (delays as well as message complexity) are compared. Related issues such as correctness of the algorithms, performance of the algorithms, and deadlock resolution, which require further research are examined     

Deadlock detection without wait-for graphs

Deadlock detection is an important service that the run-time system of a parallel environment should provide. In parallel programs deadlock can occur when the different processes are waiting for various events, as opposed to concurrent systems, where deadlock occurs when processes wait for resources held by other processes. Therefore classical deadlock detection techniques such as checking for cycles in the wait-for graph are unapplicable. An alternative algorithm that checks whether all the processes are blocked is presented. This algorithm deals with situations in which the state transition from blocked to unblocked is indirect, as may happen when busy-waiting is used.     

On Deadlock Detection in Distributed Systems

A hierarchically organized and a distributed protocol for deadlock detection in distributed databases are presented in [1]. In this paper we show that the distributed protocol is incorrect, and present possible remedies. However, the distributed protocol remains impractical because "condensations" of "transaction-wait-for" graphs make graph updates difficult to perform. Delayed graph updates cause the occurrence of false deadlocks in this as well as in some other deadlock detection protocols for distributed systems. The performance degradation that results from false deadlocks depends on the characteristics of each protocol.     

分布式系统死锁的预防、避免和检测

分布式系统涉及到资源和数据的高度共享,从而可能引发死锁。分布式系统的死锁是由于资源和通讯产生的。从分布式系统死锁产生的条件,解决策略,以及分布式系统中死锁预防、避免和检测的各种算法进行了具体阐述。     

Comments on "Protocols for Deadlock Detection in Distributed Database Systems"

The two-phase deadlock detection protocol in the above paperl detects false deadlocks. This is contrary to what the authors claim. The false detection o. f deadlocks is shown using a counterexample.     

MPI-RCDD: A Framework for MPI Runtime Communication Deadlock Detection

The message passing interface (MPI) has become a de facto standard for programming models of highperformance computing, but its rich and flexible interface semantics makes the program easy to generate communication deadlock, which seriously affects the usability of the system. However, the existing detection tools for MPI communication deadlock are not scalable enough to adapt to the continuous expansion of system scale. In this context, we propose a framework for MPI runtime communication deadlock detection, namely MPI-RCDD, which contains three kinds of main mechanisms. Firstly, MPI-RCDD has a message logging protocol that is associated with deadlock detection to ensure that the communication messages required for deadlock analysis are not lost. Secondly, it uses the asynchronous processing thread provided by the MPI to implement the transfer of dependencies between processes, so that multiple processes can participate in deadlock detection simultaneously, thus alleviating the performance bottleneck problem of centralized analysis. In addition, it uses an AND⊕OR model based algorithm named AODA to perform deadlock analysis work. The AODA algorithm combines the advantages of both timeout-based and dependency-based deadlock analysis approaches, and allows the processes in the timeout state to search for a deadlock circle or knot in the process of dependency transfer. Further, the AODA algorithm cannot lead to false positives and can represent the source of the deadlock accurately. The experimental results on typical MPI communication deadlock benchmarks such as Umpire Test Suit demonstrate the capability of MPIRCDD. Additionally, the experiments on the NPB benchmarks obtain the satisfying performance cost, which show that the MPI-RCDD has strong scalability.     

容错的分布式系统通用死锁模型检测解除算法

分布式系统技术为采用低成本购建高性能系统提供了有效的途径,但是由于资源的分配与需求可能产生冲突,造成系统中发生死锁,导致系统运行陷入停滞.在不可靠的分布式系统中,故障会干扰正常的死锁检测,但现有的死锁检测算法不具有容错功能.对失效形式进行了归类,提出一个容错的死锁检测解除算法.算法建立在通用的AND-OR模型基础上,采用扩散计算和集中规约方式,不仅能够检测到死锁,而且能给出死锁环的全部成员.若死锁拓扑处于静态且为环状,算法的消息复杂度的上限为e n-1,时间复杂度为d,其中e为死锁等待图中边的个数,n和d为构成死锁环的节点的个数,分析表明算法性能等于或优于同类算法.