Operating Systems Chapter 5: Concurrency and Synchronization
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Questions and Answers

What is the primary concern of Operating System design?

  • Management of processes and threads (correct)
  • Development of applications software
  • Optimization of computer networks
  • Management of computer hardware

    • What is the main difficulty in managing concurrent processing?

  • Handling interrupts generated by devices
  • Sharing of global resources among processes (correct)
  • Scheduling of processes by the OS
  • Predicting the relative speed of execution of processes

    • In a uniprocessor system, what makes it difficult to predict the relative speed of execution of processes?

  • The OS handles interrupts
  • The scheduling policies of the OS
  • The activities of other processes (correct)
  • All of the above

    • What is the outcome of a race condition in concurrent processing?

    <p>The process that updates last determines the final value of the variable</p> Signup and view all the answers

    What is the main challenge in debugging concurrent programs?

    <p>The results are not deterministic and reproducible</p> Signup and view all the answers

    What is the main concern of Operating System design in terms of concurrency?

    <p>To design and manage concurrent processing</p> Signup and view all the answers

    What is a fundamental requirement for processes to interact with each other?

    <p>Synchronization and communication</p> Signup and view all the answers

    What is the purpose of semWait and semSignal operations in implementing semaphores?

    <p>To ensure atomicity</p> Signup and view all the answers

    What is a characteristic of a non-blocking send in message passing?

    <p>The sender continues on without waiting for the message to be delivered</p> Signup and view all the answers

    What is the purpose of the receive primitive in message passing?

    <p>To receive information from another process</p> Signup and view all the answers

    What is an approach to providing both synchronization and communication between processes?

    <p>Message Passing</p> Signup and view all the answers

    Why is it imperative to implement semWait and semSignal operations as atomic primitives?

    <p>To guarantee the correctness of the semaphore implementation</p> Signup and view all the answers

    What is the primary purpose of a semaphore?

    <p>To ensure mutual exclusion in a multi-process environment</p> Signup and view all the answers

    Which of the following is a characteristic of a strong semaphore?

    <p>The process that has been blocked the longest is released from the queue first</p> Signup and view all the answers

    In the producer/consumer problem, what is the primary constraint on the buffer?

    <p>Only one producer or consumer can access the buffer at any one time</p> Signup and view all the answers

    What is the primary goal of allocating and de-allocating resources for each active process?

    <p>To protect the data and physical resources of each process against interference by other processes</p> Signup and view all the answers

    What is the consequence of decrementing a semaphore in a uniprocessor system?

    <p>It is unknown whether the process will block or not</p> Signup and view all the answers

    What is the primary function of the semWait operation?

    <p>To decrement the value of the semaphore</p> Signup and view all the answers

    What is the primary reason why concurrent processes come into conflict?

    <p>Because of competition for use of the same resource</p> Signup and view all the answers

    What is the purpose of the queue in a semaphore implementation?

    <p>To hold the processes waiting on the semaphore</p> Signup and view all the answers

    What is the primary goal of implementing mutual exclusion?

    <p>To prevent a process from being denied access to a critical section when there is no other process using it</p> Signup and view all the answers

    What is the drawback of disabling interrupts to guarantee mutual exclusion in a uniprocessor system?

    <p>It may degrade the efficiency of execution</p> Signup and view all the answers

    What is the Compare&Swap Instruction used for?

    <p>To compare and exchange values in a memory</p> Signup and view all the answers

    What is the main advantage of using Special Machine Instructions for mutual exclusion?

    <p>It can be carried out atomically</p> Signup and view all the answers

    What is the primary goal of a nonblocking send operation?

    <p>To allow the sender to continue processing without waiting</p> Signup and view all the answers

    In direct addressing, how is the source of the message typically identified?

    <p>Through an implicit source parameter in the receive primitive</p> Signup and view all the answers

    What is the primary benefit of using indirect addressing in message passing?

    <p>Greater flexibility in the use of messages</p> Signup and view all the answers

    In a message passing system, what is the purpose of a mailbox?

    <p>To provide a shared data structure for multiple processes</p> Signup and view all the answers

    What is a common problem in concurrent processing that can be addressed using message passing?

    <p>Mutual exclusion</p> Signup and view all the answers

    Which type of process exists solely to provide a service or resource to other processes?

    <p>Service process</p> Signup and view all the answers

    Study Notes

    Operating System Design and Concurrency

    • Operating System design is concerned with the management of processes and threads
    • Multiple applications are invented to allow processing time to be shared among active applications
    • Structured Applications are an extension of modular design and structured programming

    Operating System Structure

    • Operating Systems themselves are implemented as a set of processes or threads
    • Interleaving and overlapping can be viewed as examples of concurrent processing

    Difficulties of Concurrency

    • Sharing of global resources
    • Difficulty for the OS to manage the allocation of resources optimally
    • Difficulty in locating programming errors as results are not deterministic and reproducible
    • Occurs when multiple processes or threads read and write data items
    • The final result depends on the order of execution

    Operating System Concerns

    • Design and management issues raised by the existence of concurrency
    • The OS must be able to:
      • Manage the allocation of resources
      • Prevent interference between processes
      • Ensure that the processes and outputs are independent of the processing speed

    Mutual Exclusion

    • Mutual exclusion is necessary to ensure that only one process or thread can access a shared resource at a time
    • Implemented using binary semaphores or other mechanisms
    • A solution to the bounded-buffer producer/consumer problem using semaphores is shown in Figure 5.13

    Semaphores

    • A semaphore is a variable that has an integer value upon which only three operations are defined:
      • Initialize to a nonnegative integer value
      • Decrement the value (semWait)
      • Increment the value (semSignal)
    • There is no way to inspect or manipulate semaphores other than these three operations
    • Consequences of using semaphores:
      • No way to know before a process decrements a semaphore whether it will block or not
      • No way to know which process will continue immediately on a uniprocessor system when two processes are running concurrently
      • Don't know whether another process is waiting, so the number of unblocked processes may be zero or one

    Message Passing

    • Message passing is one approach to providing both synchronization and communication
    • Works with distributed systems and shared memory multiprocessor and uniprocessor systems
    • The actual function is normally provided in the form of a pair of primitives:
      • send (destination, message)
      • receive (source, message)
    • A process sends information in the form of a message to another process designated by a destination
    • A process receives information by executing the receive primitive, indicating the source and the message
    • Both sender and receiver are blocked until the message is delivered

    Non-Blocking Send and Receive

    • Non-blocking send, blocking receive: sender continues on but receiver is blocked
    • Non-blocking send, non-blocking receive: neither party is required to wait

    Mutual Exclusion Using Message Passing

    • A solution to the bounded-buffer producer/consumer problem using messages is shown in Figure 5.21

    Readers/Writers Problem

    • A data area is shared among many processes
    • Some processes only read the data area (readers) and some only write to the data area (writers)
    • Conditions that must be satisfied:
      • No reader can access the data area while a writer is accessing it
      • No writer can access the data area while a reader is accessing it
      • No writer can access the data area while another writer is accessing it

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    Test your knowledge on Operating System design principles, focusing on concurrency, mutual exclusion, and synchronization. Learn about multiprogramming, multiprocessing, and distributed processing in this chapter 5 quiz from William Stallings' Seventh Edition.

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