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Lecture Operating system concepts (9/ed) - Chapter 7: Deadlocks

In this chapter, the following content will be discussed: System model, deadlock characterization, methods for handling deadlocks, deadlock prevention, deadlock avoidance, deadlock detection, recovery from deadlock. | Chapter 7: Deadlocks Chapter 7: Deadlocks System Model Deadlock Characterization Methods for Handling Deadlocks Deadlock Prevention Deadlock Avoidance Deadlock Detection Recovery from Deadlock Chapter Objectives To develop a description of deadlocks, which prevent sets of concurrent processes from completing their tasks To present a number of different methods for preventing or avoiding deadlocks in a computer system System Model System consists of resources Resource types R1, R2, . . ., Rm CPU cycles, memory space, I/O devices Each resource type Ri has Wi instances. Each process utilizes a resource as follows: request use Release // sử dụng trong trả lại Deadlock Characterization Mutual exclusion: only one process at a time can use a resource //tranh chấp đường đi Hold and wait: a process holding at least one resource is waiting to acquire additional resources held by other processes //đang giữ thì chờ No preemption: a resource can be released only voluntarily by the | Chapter 7: Deadlocks Chapter 7: Deadlocks System Model Deadlock Characterization Methods for Handling Deadlocks Deadlock Prevention Deadlock Avoidance Deadlock Detection Recovery from Deadlock Chapter Objectives To develop a description of deadlocks, which prevent sets of concurrent processes from completing their tasks To present a number of different methods for preventing or avoiding deadlocks in a computer system System Model System consists of resources Resource types R1, R2, . . ., Rm CPU cycles, memory space, I/O devices Each resource type Ri has Wi instances. Each process utilizes a resource as follows: request use Release // sử dụng trong trả lại Deadlock Characterization Mutual exclusion: only one process at a time can use a resource //tranh chấp đường đi Hold and wait: a process holding at least one resource is waiting to acquire additional resources held by other processes //đang giữ thì chờ No preemption: a resource can be released only voluntarily by the process holding it, after that process has completed its task //giữ thì ko trả tài nguyên Circular wait: there exists a set {P0, P1, , Pn} of waiting processes such that P0 is waiting for a resource that is held by P1, P1 is waiting for a resource that is held by P2, , Pn–1 is waiting for a resource that is held by Pn, and Pn is waiting for a resource that is held by P0. // Deadlock can arise if four conditions hold simultaneously. Deadlock with Mutex Locks Deadlocks can occur via system calls, locking, etc. See example box in text page 318 for mutex deadlock Resource-Allocation Graph V is partitioned into two types: P = {P1, P2, , Pn}, the set consisting of all the processes in the system R = {R1, R2, , Rm}, the set consisting of all resource types in the system request edge – directed edge Pi Rj assignment edge – directed edge Rj Pi A set of vertices V and a set of edges E. Resource-Allocation Graph (Cont.) Process Resource Type with 4 instances Pi requests .