软件操作系统教学（ANDREW S. TANENBAUM）MOS-Ch06-e3.pptVIP

死锁的检测 死锁检测算法 Remarks 银行家算法(Cont.) 银行家算法(Cont.) 资源分配 安全性检测算法 银行家算法例子 银行家算法例子 银行家算法的保守性 银行家算法的保守性 讨论 Figure 6-7. An example for the deadlock detection algorithm. Deadlock Detection with Multiple Resources of Each Type (3) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639 Recovery from Deadlock Recovery through preemption Recovery through rollback Recovery through killing processes Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639 Figure 6-8. Two process resource trajectories. Deadlock Avoidance Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639 Figure 6-9. Demonstration that the state in (a) is safe. Safe and Unsafe States (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639 Figure 6-10. Demonstration that the state in (b) is not safe. Safe and Unsafe States (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639 数据结构： Available: array[1..m]of integer; //系统可用资源 Claim: array[1..n,1..m]of integer; //进程最大需求 Allocation: array[1..n,1..m]of integer; //当前分配 Need: array[1..n,1..m]of integer; //尚需资源 Request: array[1..n,1..m]of integer; //当前请求 临时变量： Work: array[1..m]of integer; Finish: array[1..n]of boolean; 设X,Y为下标1..l的一维数组： X?Y ? ?j (1?j?l), X[j]?Y[j] X:=Y ? ?j (1?j?l), X[j]:=Y[j] X:=c ? ?j (1?j?l), X[j]:=c X±Y ? ?j (1?j?l), X[j]±Y[j] Pi请求资源 Request[I]?Need[I] 请求超量，错返 Request[I]?Available 不满足，等待 Available:=Available-Request[I] Allocation[I]:=Allocation[I]+Request[I] Need[I]:=Need[I]-Request[I] 安全 确认，pi继续 Available:=Available+Request[I] Allocation[I]:=Allocation[I]-Request[I] Need[I]:=Need[I]+Request[I] pi等待 F T F T T F F Work:=Available; Finish:=false; 有满足条件的j: Finish[j]=false Need[j]?Work Finish[j]=true; Work:=Work+Allocation[j] T ?j ,finis