Ch8 OS

Chapter 8: Deadlocks ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

The Deadlock Problem ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

System Model ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Deadlock Characterization ,[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts Deadlock can arise if four conditions hold simultaneously.

Resource-Allocation Graph ,[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts A set of vertices V and a set of edges E .

Resource-Allocation Graph (Cont.) ,[object Object],[object Object],[object Object],[object Object],Operating System Concepts P i P i R j R j

Example of a Resource Allocation Graph Operating System Concepts

Resource Allocation Graph With A Deadlock Operating System Concepts

Resource Allocation Graph With A Cycle But No Deadlock Operating System Concepts

Basic Facts ,[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Methods for Handling Deadlocks ,[object Object],[object Object],[object Object],Operating System Concepts

Deadlock Prevention ,[object Object],[object Object],[object Object],[object Object],Operating System Concepts Restrain the ways request can be made.

Deadlock Prevention (Cont.) ,[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Deadlock Avoidance ,[object Object],[object Object],[object Object],Operating System Concepts Requires that the system has some additional a priori information available.

Safe State ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Basic Facts ,[object Object],[object Object],[object Object],Operating System Concepts

Safe, Unsafe , Deadlock State Operating System Concepts

Resource-Allocation Graph Algorithm ,[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Resource-Allocation Graph For Deadlock Avoidance Operating System Concepts

Unsafe State In Resource-Allocation Graph Operating System Concepts

Banker’s Algorithm ,[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Data Structures for the Banker’s Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts Let n = number of processes, and m = number of resources types.

Safety Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Resource-Request Algorithm for Process P i ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Example of Banker’s Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Example (Cont.) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Example P 1 Request (1,0,2) (Cont.) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Deadlock Detection ,[object Object],[object Object],[object Object],Operating System Concepts

Single Instance of Each Resource Type ,[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Resource-Allocation Graph and Wait-for Graph Operating System Concepts Resource-Allocation Graph Corresponding wait-for graph

Several Instances of a Resource Type ,[object Object],[object Object],[object Object],Operating System Concepts

Detection Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Detection Algorithm (Cont.) ,[object Object],[object Object],Operating System Concepts

Example of Detection Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Example (Cont.) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Detection-Algorithm Usage ,[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Recovery from Deadlock: Process Termination ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Operating System Concepts

Recovery from Deadlock: Resource Preemption ,[object Object],[object Object],[object Object],Operating System Concepts

Ch8 OS

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Ch8 OS