Conflict Resolution in Computer Systems

• Main Author: G. P. Mojarov
• Format: Article
• Language: Russian
• Published: MGTU im. N.È. Baumana 2015-01-01
• Series: Nauka i Obrazovanie
• Subjects: computer system; conflicts in computer systems; multicriterion problems; optimum strategy; deadlocks; prevention of impasses
• Online Access: http://technomag.edu.ru/jour/article/view/214

<p>A conflict situation in computer systems CS) is the phenomenon arising when the processes have multi-access to the shared resources and none of the involved processes can proceed because of their waiting for the certain resources locked by the other processes which, in turn, are in a similar position. The conflict situation is also called a deadlock that has quite clear impact on the CS state.</p><p>To find the reduced to practice algorithms to resolve the impasses is of significant applied importance for ensuring information security of computing process and thereupon the presented article is aimed at solving a relevant problem.</p><p>The gravity of situation depends on the types of processes in a deadlock, types of used resources, number of processes, and a lot of other factors.</p><p>A disadvantage of the method for preventing the impasses used in many modern operating systems and based on the preliminary planning resources required for the process is obvious - waiting time can be overlong. The preventing method with the process interruption and deallocation of its resources is very specific and a little effective, when there is a set of the polytypic resources requested dynamically. The drawback of another method, to prevent a deadlock by ordering resources, consists in restriction of possible sequences of resource requests.</p><p>A different way of "struggle" against deadlocks is a prevention of impasses. In the future a prediction of appearing impasses is supposed. There are known methods [1,4,5] to define and prevent conditions under which deadlocks may occur. Thus the preliminary information on what resources a running process can request is used. Before allocating a free resource to the process, a test for a state “safety” condition is provided. The state is "safe" if in the future impasses cannot occur as a result of resource allocation to the process. Otherwise the state is considered to be " hazardous ", and resource allocation is postponed. The obvious shortcoming in preventing impasses is a need to have a priori information on the future demand for resources, and it is not always possible.</p><p>One of ways to "struggle" against impasses when there is no a priori information on the process demand for resources is to detect deadlocks. Detection of impasses (without leading to their resolution yet) is a periodical use of the algorithm which checks current distribution of resources to reveal whether there is an impasse and if it exists what processes are involved in it.</p><p>The work objective is to develop methods and algorithms allowing us to minimize losses because of impasses in CS using the optimum strategy of conflict resolution. The offered approach is especially effective to eliminate deadlocks in management (control) computer systems having a fixed set of programmes.</p><p>The article offers a developed efficient strategy of the information processes management in multiprocessing CS, which detects and prevents impasses. The strategy is based on allocation of indivisible resources to computing processes so that losses caused by conflicts are minimized. The article studies a multi-criterion problem of indivisible resources allocation to the processes, with the optimality principle expressed by the known binary relation over set of average vectors of penalties for conflicts in each of resources. It is shown that sharing a decision theory tool and a classical one allows more efficient problem solution to eliminate deadlock. The feature of suggesting effective methods and algorithms to eliminate deadlocks is that they can be used in CS development and operation in real time. The article-given example shows that the proposed method and algorithm for the impasse resolution in multiprocessing CS are capable and promising.</p><p>The offered method and algorithm provide reducing the average number of CS conflicts by 30-40 %.</p>