Chapter 5: Process Synchronization
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Questions and Answers

What is the primary advantage of using atomic hardware instructions in modern machines?

  • They are not scalable
  • They are non-interruptible (correct)
  • They are interruptible
  • They are only used for multiprocessor systems
  • Why are the previous solutions to the critical section problem complicated and inaccessible to application programmers?

  • Because they are too simple
  • Because they are generally inaccessible to application programmers (correct)
  • Because they are not scalable
  • Because they require atomic hardware instructions
  • What is the purpose of acquiring a mutex lock?

  • To swap contents of two memory words
  • To protect a critical section (correct)
  • To release a critical section
  • To test and set a memory word
  • What is the characteristic of spinlocks?

    <p>They use busy waiting</p> Signup and view all the answers

    What is the primary difference between mutex locks and semaphores?

    <p>Semaphores provide more sophisticated ways for process synchronization</p> Signup and view all the answers

    Why are atomic instructions necessary for implementing mutex locks?

    <p>To ensure that calls to acquire() and release() are atomic</p> Signup and view all the answers

    What is the primary problem with using uniprocessors to protect critical regions?

    <p>They are generally inefficient on multiprocessor systems</p> Signup and view all the answers

    What is the main advantage of using mutex locks over previous solutions?

    <p>They are simpler and more accessible to application programmers</p> Signup and view all the answers

    What is the purpose of the release() function in mutex locks?

    <p>To release a critical section</p> Signup and view all the answers

    Why are special atomic hardware instructions necessary in modern machines?

    <p>To ensure that certain operations are executed as a single, uninterruptible unit</p> Signup and view all the answers

    Study Notes

    Process Synchronization

    • Process synchronization is necessary to maintain data consistency in concurrent execution environments.

    The Critical-Section Problem

    • The critical-section problem arises when multiple processes access shared data concurrently, leading to data inconsistency.
    • The problem involves designing a protocol to ensure that only one process can execute its critical section at a time.

    Solution to Critical-Section Problem

    • The solution must satisfy three conditions: • Mutual Exclusion: no two processes can execute their critical sections simultaneously. • Progress: a process waiting to enter its critical section will eventually do so. • Bounded Waiting: a limit exists on the number of times other processes can enter their critical sections before the waiting process enters its critical section.

    Critical Section Handling in OS

    • Two approaches to critical-section handling exist, depending on whether the kernel is preemptive or non-preemptive.
    • Preemptive kernel: allows preemption of a process when running in kernel mode.
    • Non-preemptive kernel: runs until it exits kernel mode, blocks, or voluntarily yields CPU.

    Synchronization Hardware

    • Many systems provide hardware support for implementing critical section code using locks.
    • Uniprocessors can disable interrupts to protect critical regions, but this approach is inefficient on multiprocessor systems.

    Mutex Locks

    • Mutex locks are software tools that solve the critical section problem.
    • A mutex lock protects a critical section by requiring a process to acquire the lock before entering the critical section and releasing it afterwards.
    • Mutex locks can be implemented using hardware atomic instructions, but they require busy waiting, making them spinlocks.

    Semaphore

    • Semaphore is a synchronization tool that provides more sophisticated ways to synchronize process activities than mutex locks.

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    Description

    This quiz covers the concepts of process synchronization, including critical sections, Peterson's solution, and synchronization hardware, based on the 9th edition of Operating System Concepts by Silberschatz, Galvin, and Gagne.

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