MODERN OPERATING SYSTEMS Third Edition ANDREW S. TANENBAUM Chapter 6 Deadlocks Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All.

Slides:



Advertisements
Similar presentations
Deadlocks Today Resources & deadlocks Dealing with deadlocks Other issues Next Time Memory management.
Advertisements

MODERN OPERATING SYSTEMS Third Edition ANDREW S
Ceng Operating Systems Chapter 2.4 : Deadlocks Process concept  Process scheduling  Interprocess communication  Deadlocks Threads.
Operating Systems COMP 4850/CISG 5550 Deadlock Avoidance Dr. James Money.
Chapter 3 Deadlocks TOPICS Resource Deadlocks The ostrich algorithm
MODERN OPERATING SYSTEMS Third Edition ANDREW S. TANENBAUM Chapter 6 Deadlocks Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All.
1 Deadlocks Chapter Resource 3.2. Introduction to deadlocks 3.3. The ostrich algorithm 3.4. Deadlock detection and recovery 3.5. Deadlock avoidance.
Tanenbaum Ch 6 Silberschatz Ch 7
5/25/2015Page 1 Deadlock Management B. Ramamurthy.
DEADLOCK.
Chapter 3 Deadlocks - Αδιέξοδα 3.1. Resource
With slides from C. Griwodz, K. Li, A. Tanenbaum and M. van Steen
Avishai Wool lecture Introduction to Systems Programming Lecture 5 Deadlocks.
DPNM Lab. Dept. of CSE, POSTECH
Deadlock Chapter 3 R1 R2 P2P1 Allocated Requested.
Deadlocks Tore Larsen With slides from T. Plagemann, C. Griwodz, K. Li, A. Tanenbaum and M. van Steen.
Mehdi Naghavi Spring 1386 Operating Systems Mehdi Naghavi Spring 1386.
Chapter 3: Deadlocks Chapter 3 2 CMPS 111, UC Santa Cruz Overview  Resources  Why do deadlocks occur?  Dealing with deadlocks Ignoring them: ostrich.
1 CS 333 Introduction to Operating Systems Class 7 - Deadlock Jonathan Walpole Computer Science Portland State University.
The Banker’s Algorithm for A Single Resource
Deadlock CSCI 444/544 Operating Systems Fall 2008.
Chapter 3 Deadlocks 3.1. Resource 3.2. Introduction to deadlocks
Deadlock Detection with One Resource of Each Type (1)
Chapter 6 Deadlocks Resources Introduction Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved
CS450/550 Deadlocks.1 Adapted from MOS2E UC. Colorado Springs CS450/550 Operating Systems Lecture 3 Deadlocks Palden Lama Department of Computer Science.
Chapter 3 Chapter 3: Deadlocks Chapter 3 2 CS 1550, cs.pitt.edu (originaly modified by Ethan L. Miller and Scott A. Brandt) Overview Resources Why do.
Deadlocks.
Deadlock Chapter 3 Thursday, February 22, Today’s Schedule Assignment #4 from Chapter 3 posted Deadlock - Chapter 3  Skip multiple resources (3.4.2.
1 Processes, Threads, Race Conditions & Deadlocks Operating Systems Review.
CH 3 Deadlock When 2 (or more) processes remain blocked forever!
1 Deadlocks Chapter Resource 3.2. Introduction to deadlocks 3.3. The ostrich algorithm 3.4. Deadlock detection and recovery 3.5. Deadlock avoidance.
Chapter 3: Deadlocks. CMPS 111, Fall Overview ✦ Resources ✦ Why do deadlocks occur? ✦ Dealing with deadlocks Ignoring them: ostrich algorithm Detecting.
Overview Resources Why do deadlocks occur? Dealing with deadlocks Ignoring them: ostrich algorithm Detecting & recovering from deadlock Avoiding deadlock.
1 Deadlocks Chapter Resource 3.2. Introduction to deadlocks 3.4. Deadlock detection and recovery 3.5. Deadlock avoidance 3.6. Deadlock prevention.
1 Deadlocks 2 Resources Examples of computer resources –printers –tape drives –tables Processes need access to resources in reasonable order Suppose.
1 Deadlocks Chapter Resource 3.2. Introduction to deadlocks 3.3. The ostrich algorithm 3.4. Deadlock detection and recovery 3.5. Deadlock avoidance.
1 Deadlocks Chapter 3. 2 Resources Examples of computer resources –printers –tape drives –tables Processes need access to resources in reasonable order.
1 Pertemuan 10 Deadlock (lanjutan) Matakuliah: T0316/sistem Operasi Tahun: 2005 Versi/Revisi: 5.
Operating Systems 软件学院 高海昌 Operating Systems Gao Haichang, Software School, Xidian University 22 Contents  1. Introduction** 
1 Deadlock Definition of deadlock Condition for its occurrence Solutions for avoiding and breaking deadlock –Deadlock Prevention –Deadlock Avoidance –Deadlock.
1 Deadlocks Chapter Resource 3.2. Introduction to deadlocks 3.3. The ostrich algorithm 3.4. Deadlock detection and recovery 3.5. Deadlock avoidance.
Operating Systems (OS)
1 MODERN OPERATING SYSTEMS Third Edition ANDREW S. TANENBAUM Chapter 6 Deadlocks Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc.
Deadlocks. What is a Deadlock “A set of processes is deadlocked if each process in the set is waiting for an event that only another process in the set.
CSC 322 Operating Systems Concepts Lecture - 28: by Ahmed Mumtaz Mustehsan Special Thanks To: Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall,
Deadlocks System Model RAG Deadlock Characterization
CS333 Intro to Operating Systems Jonathan Walpole.
Operating Systems COMP 4850/CISG 5550 Deadlocks Dr. James Money.
CH 3 Deadlock When 2 (or more) processes remain blocked forever!
Deadlocks References –text: Tanenbaum ch.3. Deadly Embrace Deadlock definition –A set of process is dead locked if each process in the set is waiting.
Deadlocks Chapter 6 Tanenbaum & Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved.
Sistem Operasi IKH311 Deadlock. 2 Resources Examples of computer resources printers tape drives tables Processes need access to resources in reasonable.
Deadlocks Lots of resources can only be used by one process at a time. Exclusive access is needed. Suppose process A needs R1 + R2 and B needs R1 + R2.
Operating Systems Chapter 3: Deadlocks
MODERN OPERATING SYSTEMS Third Edition ANDREW S
Chapter 6 : Deadlocks What is a Deadlock?
Deadlocks References text: Tanenbaum ch.3.
Lecture 19: Deadlock: Conditions, Detection and Avoidance
Deadlocks References text: Tanenbaum ch.3.
Chapter 3 Deadlocks 3.1. Resource 3.2. Introduction to deadlocks
DPNM Lab. Dept. of CSE, POSTECH
MODERN OPERATING SYSTEMS Third Edition ANDREW S
Chapter 3 Deadlocks 3.1. Resource 3.2. Introduction to deadlocks
Lecture 19: Deadlock: Conditions, Detection and Avoidance
Chapter 3 Deadlocks 3.1. Resource 3.2. Introduction to deadlocks
Introduction to Deadlocks
Chapter 3 Deadlocks 3.1. Resource 3.2. Introduction to deadlocks
Deadlocks References text: Tanenbaum ch.3.
MODERN OPERATING SYSTEMS Third Edition ANDREW S
Chapter 3 Deadlocks -For MCA, PU
Presentation transcript:

MODERN OPERATING SYSTEMS Third Edition ANDREW S. TANENBAUM Chapter 6 Deadlocks Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Preemptable and Nonpreemptable Resources Sequence of events required to use a resource: 1.Request the resource. 2.Use the resource. 3.Release the resource. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure 6-1. Using a semaphore to protect resources. (a) One resource. (b) Two resources. Resource Acquisition (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure 6-2. (a) Deadlock-free code. Resource Acquisition (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure 6-2. (b) Code with a potential deadlock. Resource Acquisition (3) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Introduction To Deadlocks Deadlock can be defined formally as follows: A set of two or more threads is deadlocked if each thread in the set is waiting (blocked) for an event that only another thread in the set can cause. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Conditions for Resource Deadlocks 1.Mutual exclusion condition A resource is assigned to exactly 1 thread or it is available 2.Hold and wait condition. a thread may hold resources while requesting additional resources 3.No preemption condition. previously granted resources cannot forcibly be taken away 4.Circular wait condition. must be a circular chain of 2 or more threads. each is waiting for resource held by next member of the chain Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved Coffman, E.G., Elphick, M.J. and Shoshani, A.

Figure 6-3. Resource allocation graphs. (a) Holding a resource. (b) Requesting a resource. (c) Deadlock. Deadlock Modeling (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure 6-4. An example of how deadlock occurs and how it can be avoided. Deadlock Modeling (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure 6-4. An example of how deadlock occurs and how it can be avoided. Deadlock Modeling (3) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure 6-4. An example of how deadlock occurs and how it can be avoided. Deadlock Modeling (4) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Deadlock Strategies Four strategies for dealing with deadlocks: 1.Just ignore the problem 2.Detection and recovery 3.Dynamic avoidance 4.Prevention Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

13 The Ostrich Algorithm Just ignore the problem - Pretend there is no problem Reasonable if –deadlocks occur very rarely –cost of prevention is high UNIX and Windows take this approach It is a trade off between –convenience –correctness

Detection and Recovery Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure 6-5. (a) A resource graph. (b) A cycle extracted from (a). Deadlock Detection with One Resource of Each Type (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Deadlock Detection with One Resource of Each Type (2) Algorithm for detecting deadlock: 1.For each node, N in the graph, perform the following five steps with N as the starting node. 2.Initialize L to the empty list, designate all arcs as unmarked. 3.Add current node to end of L, check to see if node now appears in L two times. If it does, graph contains a cycle (listed in L), algorithm terminates. … Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Deadlock Detection with One Resource of Each Type (3) 4.From given node, see if any unmarked outgoing arcs. If so, go to step 5; if not, go to step 6. 5.Pick an unmarked outgoing arc at random and mark it. Then follow it to the new current node and go to step 3. 6.If this is initial node, graph does not contain any cycles, algorithm terminates. Otherwise, dead end. Remove it, go back to previous node, make that one current node, go to step 3. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure 6-6. The four data structures needed by the deadlock detection algorithm. Deadlock Detection with Multiple Resources of Each Type (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Deadlock Detection with Multiple Resources of Each Type (2) Deadlock detection algorithm: 1.Look for an unmarked process, P i, for which the i-th row of R is less than or equal to A. 2.If such a process is found, add the i-th row of C to A, mark the process, and go back to step 1. 3.If no such process exists, the algorithm terminates. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

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

21 Recovery from Deadlock (1) Recovery through preemption –take a resource from some other process –depends on nature of the resource Recovery through rollback –checkpoint a process periodically –use this saved state –restart the process if it is found deadlocked Recovery through killing processes –crudest but simplest way to break a deadlock –kill one of the processes in the deadlock cycle –the other processes get its resources –choose process that can be rerun from the beginning

22

Figure 6-8. Two process resource trajectories. Deadlock Avoidance Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

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

Figure 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

Figure Three resource allocation states: (a) Safe. (b) Safe. (c) Unsafe. The Banker’s Algorithm for a Single Resource Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure The banker’s algorithm with multiple resources. The Banker’s Algorithm for Multiple Resources (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

The Banker’s Algorithm for Multiple Resources (2) Algorithm for checking to see if a state is safe: 1.Look for row, R, whose unmet resource needs all ≤ A. If no such row exists, system will eventually deadlock since no process can run to completion 2.Assume process of row chosen requests all resources it needs and finishes. Mark process as terminated, add all its resources to the A vector. 3.Repeat steps 1 and 2 until either all processes marked terminated (initial state was safe) or no process left whose resource needs can be met (there is a deadlock). Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Deadlock Prevention Attacking the mutual exclusion condition Attacking the hold and wait condition Attacking the no preemption condition Attacking the circular wait condition Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

30 Deadlock Prevention Attacking the Mutual Exclusion Condition Some devices (such as printer) can be spooled –only the printer daemon uses printer resource –thus deadlock for printer eliminated Not all devices can be spooled Principle: –avoid assigning resource when not absolutely necessary –as few processes as possible actually claim the resource

31 Attacking the Hold and Wait Condition Require processes to request resources before starting –a process never has to wait for what it needs Problems –may not know required resources at start of run –also ties up resources other processes could be using Variation: –process must give up all resources –then request all immediately needed

32 Attacking the No Preemption Condition This is not a viable option Consider taking away a printer owned by another process –halfway through its job –now forcibly take away printer –!!??

Figure (a) Numerically ordered resources. (b) A resource graph. Attacking the Circular Wait Condition Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure Summary of approaches to deadlock prevention. Approaches to Deadlock Prevention Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Other Issues Two-phase locking Communication deadlocks Livelock Starvation Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure A resource deadlock in a network. Communication Deadlocks Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved

Figure Busy waiting that can lead to livelock. Livelock Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved