1. IT320 Operating System Concepts
Unit 4: Processes, Threads & Deadlocks
June 2011
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2. Unit 4 Overview Readings Discussion Questions Assignments
Lecture on Processes, Threads & Deadlocks
Prepping your computer for simulations
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3. Unit 4: Reading & Assignments
Textbook Reading
Chapter 3 – Process Description & Control
Chapter 4 – Threads, SMP, & Microkernels
Chapter 6 – Concurrency: Deadlocks & Starvation
Start with chapter summaries first!
Web Articles Reading
2 Discussion Questions
4 page essay (due Tuesday)
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4. Unit 4: Discussion Questions
DQ1
Deadlocks are a dreaded state for modern computer systems and do take place quite often. But for deadlocks to happen, four conditions must be met. What are they? Explain.
Note: Your response should only list one condition. The responses to follow should list conditions not yet discussed.
DQ2 (optional – non-graded topic)
The second discussion thread in this unit is an opportunity for you to ask questions. Use this thread to post questions about running task manager for Linux and Windows; issues, observations, suggestions, etc...
Use this thread to post questions about running task manager for Linux and Windows: issues, observations, suggestions…
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5. Unit 4: Essay on Windows vs Linux
The project for this Unit is a “hands-on” one. You are required to submit screenshots of both your Linux and windows task managers.
You will explore the tools available for Linux and Windows for examining processes and threads and write a report in the usual APA format.
For Windows:
Download the utility “Process Monitor” in this link and run it to aid you understand more about processes running on your Windows OS
Run the utility on your Windows computer. Capture several screenshots of the interface and processes running on your PC.
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6. Unit 4: Essay on Windows vs. Linux
For Linux:
Logon to your installed distribution, open a terminal window also called Xterm, and run the command “top” without the quotation marks followed by the return key. For better results with the top command, use the “man”pages to see all available switches for you to use with top.
To do that, at theconsole type: man top “man top” is short for “manual on the top command”.
You will get several options and switches, read through them and use what you deem needed. To quit the man pages, simply type the letter “q”.
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7. Unit 4: Essay on Windows vs. Linux
Write a four-page detailed report on what you observed and relate it to what you learned about processes, threads, deadlocks, preventions, avoidance, and detection.
Be sure to submit a screen shot for each task manager output for Linux and Windows. To make screenshots, Windows users just need to press the "Print Screen" key. Mac users press Command+Shift+3.
Your paper should include at least four pages of content. Note that your paper will be longer than four pages as it will have a title page, table of contents, and a reference page in addition to the actual content pages required.
Use APA style.
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8. Unit 4: Grading Rubric
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9. Assignment Guidelines
DO NOT use Wikipedia as a source for your paper! Papers that use wiki sites as sources will lose 10% (-5 pts)
Use “quotation marks” if you are directly quoting from the sources.
1st Offense – You will be asked to rewrite the paper
2nd Offense – You will be reported to the university and the paper will receive a zero
Always include a title paper (with your name), intro, conclusion, content, & references.
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10. Chapter 3 - Processes
What is a process?
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11. What are processes? A program in execution
An instance of a program running on a computer
The entity that can be assigned to and executed on a processor
A unit of activity characterized by the execution of a sequence of instructions, a current state, and an associated set of system instructions
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12. Process Elements A process includes: Program code (possibly shared)
A set of data
A number of attributes describing the state of the process
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13. Process Elements
While the process is running it has a number of elements including
Identifier
State
Priority
Program counter
Memory pointers
Context data
I/O status information
Accounting information
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14. Process Control Block Contains the process elements
Created and managed by the operating system
Allows support for multiple processes
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15. Process State Process may be in one of two states Running Not-running
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16. Queuing Diagram
Processes are moved by the dispatcher of the OS to the CPU then back to the queue until the task is completed
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17. Five State Process Model
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18. Operating System Control Structures
For the OS is to manage processes and resources, it must have information about the current status of each process and resource.
Tables are constructed for each entity the operating system manages
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19. OS Control Tables
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20. Chapter 4 -Processes & Threads
What is a Thread?
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21. Processes & Threads Processes have two characteristics:
Resource ownership Process includes a virtual address space to hold the process image
Scheduling/execution Follows an execution path that may be interleaved with other processes
These two characteristics are treated independently by the operating system
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22. What is a thread?
The unit of dispatching is referred to as a thread or lightweight process
The unit of resource ownership is referred to as a process or task
One way to view a thread is as an independent program counter operating within a process.
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23. Threads vs. Processes
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24. Benefits of Threads
Takes less time to create a new thread than a process
Less time to terminate a thread than a process
Switching between two threads takes less time that switching processes
Threads can communicate with each other without invoking the kernel
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25. Different approaches to different threads
Differences between different Operating Systems support of processes include:
How processes are named
Whether threads are provided
How processes are represented
How process resources are protected
What mechanisms are used for inter-process communication and synchronization
How processes are related to each other
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26. Windows Processes
Processes and services provided by the Windows Kernel are relatively simple and general purpose
Implemented as objects
An executable process may contain one or more threads
Both processes and thread objects have built- in synchronization capabilities
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27. Windows Thread State
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28. Linux Tasks
A process, or task, in Linux is represented by a task_struct data structure
This contains a number of categories including:
State
Scheduling information
Identifiers
Interprocess communication
And others
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29. Linux Process/Thread Model
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30. Chapter 6 - Deadlock What is meant by the term “deadlock”?
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31. Deadlock
A set of processes is deadlocked when each process in the set is blocked awaiting an event that can only be triggered by another blocked process in the set
Typically involves processes competing for the same set of resources
No efficient solution for the general case
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32. Potential Deadlock I need quad C and B I need quad B and C
I need quad A and B
I need quad D and A
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33. Actual Deadlock HALT until D is free HALT until C is free
HALT until B is free
HALT until A is free
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34. Conditions for a Possible Deadlock
Mutual exclusion
Only one process may use a resource at a time
Hold-and-wait
A process may hold allocated resources while awaiting assignment of others
No pre-emption
No resource can be forcibly removed from a process holding it
Circular Wait
Each process is waiting for a resource held by the next process in the chain
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35. How to Deal with Deadlock
Three general approaches exist for dealing with deadlock.
Prevent Deadlock
Guarantee that one of the 4 conditions does not occur
Avoid Deadlock
Gather info from processes and require processes to declare max number of resources it might need
Detect Deadlock
Check for possible deadline by checking for resources and stop processes that might cause deadlock
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36. Unit 4: Essay on Windows vs. Linux
Write a four-page detailed report on what you observed and relate it to what you learned about processes, threads, deadlocks, preventions, avoidance, and detection.
Be sure to submit a screen shot for each task manager output for Linux and Windows. To make screenshots, Windows users just need to press the "Print Screen" key. Mac users press Command+Shift+3.
Your paper should include at least four pages of content. Note that your paper will be longer than four pages as it will have a title page, table of contents, and a reference page in addition to the actual content pages required.
Use APA style.
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37. Other Resources
Textbook imations.html
Topic Notes on Deadlock ock.pdf
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38. Any Questions? Pam Van Hook
Office Hours:
Wednesday pm ET
Sunday pm ET
AIM:
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