Basic Synchronization Principles Operating Systems Basic Synchronization Principles 1) These notes are © Aiman Hanna. All copyrights reserved. For more information please e-mail to: Contact@AimanHanna.com. 2) These notes are also based on: Operating Systems, 3rd edition by Garry Nutts, published by Addison Wesley, ISBN-10: 0201773449 | ISBN-13: 9780201773446 . These notes still totally enforce all copyrights for Nutts/ Addison Wesley. For more information on these rights, please refer to the original publication of the book. 3) VERY IMPORTANT: These notes are neither complete nor sufficient to study for the course. They are merely given so that you can follow the covered subjects. You should NEVER depend solely on these notes for your study. Any use of these notes that results in violation of any of the copyrights indicated above is strictly prohibited. © Dr. Aiman Hanna Department of Computer Science Concordia University Montreal, Canada Data Communications & Computer Networking, by: Aiman Hanna

Critical Sections (CSs) What are they? Examples of what may happen if CSs are not handled with care Examples of cooperating processes around CSs

Enabling/Disabling Interrupts Will they provide a solution to the CS problem? If yes, why cannot we depend on this solution then!

Other Solutions to the CS Problem Acquiring a lock for example How can the lock be obtained and released correctly? Examining different solutions and see why they may fail/work.

Protecting Different CSs Should one lock be used to protect different CSs? Why/Why not?

Deadlock What is it? Why is it deadly?

Evolving the CS solution Use of FORK/JOIN Synchronization

Concurrent Processes Synchronization between concurrent processes to achieve proper behavior

Semaphores What is a semaphore? How can they be used to achieve: Protection of CSs - Mutual Execution Proper synchronization/communication between concurrent processes

Where is this week coverage in the textbook? Chapter 8: Sections 8.1, 8.2 & 8.3 (until page 310), with the following exceptions: Skip: Figure 8.1 and Figure 8.2. This material however will be covered as part of the programming assignment.