CS 241 Section Week

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CS 241 Section Week 7(10/09/08)
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Topics This Section

• MP 4
• HW 2
• Exam Review

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MP 4
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MP4

• The scenario

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MP4

• The scenario

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MP4

• Request 1 (v1), (v2), (v3)

Lock Queue
Queue Data
Notify Server
Wait for Response

• Response 1 (r1)

Notified of Response
Get Response
(Prep next request)
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MP4 Forward

• Communication is done through shared memories
• client_resultclient_id
• You need to deal with three semaphores
• queue_semaphore
• To protect access to the queue
• server_notify_semaphore
• Client notify the server when data is added to
  the queue
• client_notify_semaphore
• Array of semaphores
• Client ID is used to access the semaphores
• Server notify individual client a response is
  ready

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MP4 Forward

• MP has no questions this time.
• 80 of your grade is programming.
• Make sure your program compiles and works!

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HW 2
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HW2

• Homework 2 Solutions are online
• Make sure you review your HW 2 answers w/ the
  solutions.
• Unlikely youll get HW 2 back before the exam.

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HW2

• Problem areas in HW 2
• Scheduling algorithms
• No algorithm causes deadlock.
• Some algorithms may cause starvation.
• Process forking
• When fork() is called, these are two returns!
• The following is not to process tree
  Correct Response

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Exam Review
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Exam Review

• Week 1 Introduction to C programming
• What is a C program?
• What is a pointer?
• How do you declare a pointer?
• What is heap memory?
• What is stack memory?
• What is a static variable in C?
• How is that different than Java?

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Exam Review

• Week 2 Strings and System Calls
• How is a string represented in C?
• What does strlen() do?
• What does strcpy() do?
• What does strcat() do?
• ...
• What is the difference between a system call and
  a function call?
• What is an example of a system call?
• ... a function call?

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Exam Review

• Week 3 Threads and Processes
• What is a thread?
• What is a light-weight (user-level) thread?
• How does that differ from a kernel-level thread?
• What is a process?
• What are the five states a process may be in?
• What is a zombie process? An orphan?
• How do you create threads and processes?
• pthread_create()
• fork()
• pthread_join()
• ...

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Exam Review

• Week 4 Scheduling
• Why do we have different scheduling algorithms?
• What are statistics on scheduling algorithms that
  are meaningful?
• What are some common scheduling algorithms?
• What is FCFS?
• SJF?
• PRI?
• RR?
• What is the difference between pre-emptive and
  non-pre-emptive scheduling?

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Exam Review

• Week 5 Synchronization
• Why do we need to synchronize threads/processes?
• What is a trivial example showing a
  synchronization problems?
• What are semaphores?
• What is the difference between a binary mutex and
  a counting semaphore?
• What is test_and_set()?

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Exam Review

• Week 6 Classic Synchronization
• What are OS examples showing the need for
  synchronization?
• Producer / Consumer
• Reader / Writer
• Dinning Philosophers
• What is underflow? Overflow?
• What are the four necessary conditions of
  deadlock?
• Mutual Exclusion
• Hold and Wait
• No Preemption
• Circular Wait

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Exam Review

• Week 7 Deadlocks
• How can we detect deadlocks?
• What is a resource allocation graph?
• What is a wait-for graph?
• What is
• Deadlock detection?
• Deadlock avoidance?
• Deadlock prevention?
• What do UNIX/Windows actually do?
• Ostrich Solution

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Exam Format

• In-class exam on Monday.
• Exam begins promptly at 1000am, be there early.
• Full 50 minutes for exam.
• Make sure to know which room youll be taking the
  exam in!
• All multiple choice questions
• 25-30 quick questions
• 5 longer questions
• Closed book, closed notes.
• Must bring I-Card.

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TA Review

• Optional TA Review Session
• The TAs will hold an optional review session to
  answer last-minute exam questions
  Saturday, October 11, 2008 2pm
  (whenever) 2405 SC