ch7 - perating System Concepts with Java 7 th Edition, Nov...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: perating System Concepts with Java 7 th Edition, Nov 15, 2006 Silberschatz, Galvin and Gagne 2007 Chapter 7: Deadlocks 7.2 Silberschatz, Galvin and Gagne 2007 Operating System Concepts with Java 7 th Edition, Nov 15, 2006 Chapter 7: Deadlocks The Deadlock Problem System Model Deadlock Characterization Methods for Handling Deadlocks Deadlock Prevention Deadlock Avoidance Deadlock Detection Recovery from Deadlock 7.3 Silberschatz, Galvin and Gagne 2007 Operating System Concepts with Java 7 th Edition, Nov 15, 2006 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. 7.4 Silberschatz, Galvin and Gagne 2007 Operating System Concepts with Java 7 th Edition, Nov 15, 2006 The Deadlock Problem A set of blocked processes each holding a resource and waiting to acquire a resource held by another process in the set. Example System has 2 disk drives. P 1 and P 2 each hold one disk drive and each needs another one. Example semaphores A and B , initialized to 1 P P 1 wait (A); wait(B) wait (B); wait(A) 7.5 Silberschatz, Galvin and Gagne 2007 Operating System Concepts with Java 7 th Edition, Nov 15, 2006 Bridge Crossing Example Traffic only in one direction. Each section of a bridge can be viewed as a resource. If a deadlock occurs, it can be resolved if one car backs up (preempt resources and rollback). Several cars may have to be backed up if a deadlock occurs. Starvation is possible. 7.6 Silberschatz, Galvin and Gagne 2007 Operating System Concepts with Java 7 th Edition, Nov 15, 2006 System Model Resource types R 1 , R 2 , . . ., R m CPU cycles, memory space, I/O devices Each resource type R i has W i instances. Each process utilizes a resource as follows: request use release 7.7 Silberschatz, Galvin and Gagne 2007 Operating System Concepts with Java 7 th Edition, Nov 15, 2006 Deadlock Characterization Mutual exclusion: only one process at a time can use a resource. Hold and wait: a process holding at least one resource is waiting to acquire additional resources held by other processes. No preemption: a resource can be released only voluntarily by the process holding it, after that process has completed its task. Circular wait: there exists a set { P , P 1 , , P } of waiting processes such that P 0 is waiting for a resource that is held by P 1 , P 1 is waiting for a resource that is held by P 2 , , P n 1 is waiting for a resource that is held by P n , and P is waiting for a resource that is held by P ....
View Full Document

Page1 / 48

ch7 - perating System Concepts with Java 7 th Edition, Nov...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online