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COMS 414 - Prelim 1 Review Session

COMS 414 - Prelim 1 Review Session. Multiprocessing and Synchronization Sunny( srg8@cornell.edu ) Vivek( vu22@cornell.edu ). Prelim 1. There are many, many resources available for your Prelim 1 needs: (presented in random order) Your notes! The book and its website

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COMS 414 - Prelim 1 Review Session

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  1. COMS 414 - Prelim 1 Review Session Multiprocessing and Synchronization Sunny(srg8@cornell.edu) Vivek(vu22@cornell.edu)

  2. Prelim 1 • There are many, many resources available for your Prelim 1 needs: (presented in random order) • Your notes! • The book and its website • FA2000 Homeworks/Solutions • FA2000 Prelim 1 review slides • SP2001 Lecture notes • Newsgroup • Plenty of office hours! • Additional support by appointment

  3. Before we begin … • Any questions from the CS314 review session? • Register set, stack, heap • Program counter • Interrupts / exceptions • Interrupt priority levels • Programmable I/O vs. DMA • Polling • Memory protection (base/limit)

  4. Multitasking • What is a: • Process or Task? • Thread? • What is the difference between a program and a process? • What is in the PCB? • Differences between O/S processes and user processes? • Differences between user-level threads and kernel-level threads?

  5. Multitasking • What is kernel space? • What is user space? • What is a system call? • What is a context switch? • What states may a process be in? • How do processes go between states? • What is a race condition?

  6. Synchronization • What is a critical section? • What are the three requirements for protection of a critical section? • What is busy waiting? • What are atomic instructions? • What is a semaphore?

  7. Synchronization • Three levels of abstraction for concurrent programming: • Hardware instructions • O/S functions • Programming language constructs

  8. Vivek Presents … • Classic Synchronization Problems • Monitors, Condition Variables and Language Support • Deadlocks, Prevention and Avoidance

  9. Monitors • What is a monitor? • What are condition variables? • Differentiate between semaphores and condition variables.

  10. Synchronization Problems • Bounded buffer problem • Readers writers problem • Dining philosophers problems

  11. Deadlock • What is a deadlock? • Necessary conditions for deadlock ?

  12. . . P1 P2 P3 . . R3 Deadlocks R1 R2

  13. Deadlocks R1 R2 . . P1 P2 P3 . . . R3 P4

  14. Deadlock Prevention Make sure that one of the necessary conditions does not hold -- Mutual exclusion -- Hold and Wait -- No Pre Emption -- Circular Wait

  15. Deadlock Avoidance • What is it? • What is Safe State? • Safety Check? • Bankers Algorithm

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