Operating Systems: Process Management
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Questions and Answers

What is the maximum number of elements that can be used in the bounded buffer?

  • BUFFER_SIZE / 2
  • BUFFER_SIZE
  • BUFFER_SIZE - 1 (correct)
  • BUFFER_SIZE + 1

    • What condition needs to be satisfied for the producer to add an item to the buffer?

  • (in + 1) > BUFFER_SIZE
  • in == out
  • in > out
  • (in + 1) % BUFFER_SIZE == out (correct)

    • In the consumer code, what does the condition 'in == out' signify?

  • Buffer has been completely processed
  • Buffer is at maximum capacity
  • Buffer is full
  • Buffer is empty (correct)

    • What is a major concern regarding shared memory in interprocess communication?

    <p>User process control and synchronization</p> Signup and view all the answers

    What does the term 'synchronization' refer to in the context of shared memory?

    <p>Coordinating process actions to avoid conflicts</p> Signup and view all the answers

    What operations does an interprocess communication (IPC) facility provide for message passing?

    <p>send(message) and receive(message)</p> Signup and view all the answers

    What is a key characteristic of message passing in interprocess communication?

    <p>It allows processes to communicate without shared variables.</p> Signup and view all the answers

    When processes P and Q communicate, what is the first step they must take?

    <p>Establish a communication link.</p> Signup and view all the answers

    Which of the following is NOT an implementation issue related to message passing?

    <p>How is shared memory accessed?</p> Signup and view all the answers

    In message passing, what does the capacity of a link refer to?

    <p>The number of messages a link can store temporarily.</p> Signup and view all the answers

    What call can a parent process use to terminate its child process?

    <p>abort()</p> Signup and view all the answers

    What happens to a child process if its parent process terminates without invoking wait()?

    <p>It becomes a zombie process.</p> Signup and view all the answers

    Which condition can lead a parent to terminate a child process using abort()?

    <p>The child process has exceeded its allocated resources.</p> Signup and view all the answers

    What is cascading termination in terms of process management?

    <p>All child processes are terminated when the parent terminates.</p> Signup and view all the answers

    In a multiprocess architecture such as that used by Google Chrome, what is the primary function of the browser process?

    <p>To manage user interface and I/O operations.</p> Signup and view all the answers

    What characterizes a zombie process?

    <p>It has finished execution but still has an entry in the process table.</p> Signup and view all the answers

    When a parent process exits, what happens if the operating system does not allow the child to continue?

    <p>The child process is terminated immediately.</p> Signup and view all the answers

    What do renderer processes in Chrome primarily deal with?

    <p>Rendering web pages and handling HTML.</p> Signup and view all the answers

    What is a key characteristic of a zero-capacity communication method?

    <p>The sender must wait for the receiver.</p> Signup and view all the answers

    Which statement best describes the bounded capacity communication?

    <p>The sender must wait if the link is currently full.</p> Signup and view all the answers

    In POSIX Shared Memory, what function is used to create a shared memory segment?

    <p>shm_open()</p> Signup and view all the answers

    Which system call is NOT required for message transfer in the Mach communication system?

    <p>port_allocate()</p> Signup and view all the answers

    What is the primary function of mailboxes in the Mach communication system?

    <p>To facilitate communication between tasks.</p> Signup and view all the answers

    In Windows IPC, what is the primary mechanism for communication between processes?

    <p>Advanced local procedure call (LPC).</p> Signup and view all the answers

    In a process using POSIX shared memory, which command sets the size of the shared memory object?

    <p>ftruncate()</p> Signup and view all the answers

    What happens when a Mach mailbox is full?

    <p>The sender can choose to temporarily cache the message.</p> Signup and view all the answers

    What is a characteristic of direct communication between processes?

    <p>Each link is established for exactly one pair of processes.</p> Signup and view all the answers

    Which of the following statements correctly describes indirect communication?

    <p>A single mailbox can facilitate communication between multiple processes.</p> Signup and view all the answers

    What is a property of the communication link in a direct communication system?

    <p>Links exist only if the processes explicitly name each other.</p> Signup and view all the answers

    What operations can be performed with mailboxes in indirect communication?

    <p>Create, send, receive, and destroy a mailbox.</p> Signup and view all the answers

    Which of the following statements is true regarding the sending and receiving of messages in indirect communication?

    <p>Mailboxes must be created before sending or receiving messages.</p> Signup and view all the answers

    In indirect communication, when P1 sends a message to mailbox A, what happens?

    <p>Any process sharing mailbox A can receive the message.</p> Signup and view all the answers

    What is a difference between direct and indirect communication links?

    <p>Direct communication involves explicit naming of processes, whereas indirect communication involves shared mailboxes.</p> Signup and view all the answers

    What characteristic is typical of a mailbox in an indirect communication system?

    <p>Mailboxes must have unique IDs.</p> Signup and view all the answers

    Which of the following is true about the establishment of communication links?

    <p>Communication links are established only if processes share a common mailbox in indirect communication.</p> Signup and view all the answers

    What does the message passing operation 'send(A, message)' signify?

    <p>A message is sent to a specific mailbox identified by A.</p> Signup and view all the answers

    Study Notes

    Process Termination

    • A child process can be terminated by its parent process via the abort() system call.
    • When a process terminates, all its children must also terminate, this is known as cascading termination.
    • The operating system initiates termination.
    • A parent process can wait for the termination of a child process using the wait() system call, the call returns the process ID of the terminated process and status information.
    • A process that has terminated but whose parent has not yet called wait() is called a zombie.
    • If a parent process terminates without calling wait(), the child becomes an orphan and the operating system adopts it.

    Chrome Browser

    • Google Chrome uses a multiprocess architecture, unlike other browsers that are generally single process.
    • There are 3 types of processes in Google Chrome:
      • Browser process: manages the user interface, disk, and network I/O.
      • Renderer process: renders websites, interacts with HTML and Javascript.
      • Plugin process: runs plugins in isolation from the main browser.
    • By executing the browser in a multiprocess architecture, Chrome can avoid situations where one website hangs or crashes and crashes the entire browser.

    Bounded Buffer

    • In a bounded buffer, there is a fixed amount of space available to store data.
    • The producer writes data to this buffer, and the consumer reads data from the buffer.
    • The producer can only produce data when there is space available in the buffer.
    • The consumer can only consume data when there is data available in the buffer.

    Interprocess Communication (IPC) using Shared Memory

    • IPC allows processes to communicate with each other.
    • Shared memory is a form of IPC where processes share a specific area of memory.
    • User processes control the communication in shared memory, not the operating system.
    • It's crucial to have mechanisms that allow processes to synchronize their actions when accessing shared memory. This synchronization is critical to prevent race conditions.

    Interprocess Communication (IPC) : Message Passing

    • Message passing is a mechanism for processes to both communicate and synchronize their actions.
    • It involves using messages instead of shared variables.
    • There are two operations for message passing:
      • send(message)
      • receive(message)
    • Messages can either be a fixed size or vary in size.

    Message Passing (Cont.)

    • To facilitate communication, processes need to:
      • Establish a communication link.
      • Exchange messages using send and receive.
    • The implementation of communication links is based on:
      • Physical means:
        • Shared memory
        • Hardware bus
        • Network
      • Logical means:
        • Direct or indirect communication
        • Synchronous or asynchronous communication
        • Automatic or explicit buffering

    Direct Communication

    • Processes must explicitly name each other in direct communication:
      • send (P, message) : Sends a message to process P.
      • receive(Q, message) : Receives a message from process Q.
    • Properties of Direct Communication:
      • Links are established automatically.
      • A link is associated with only one pair of communicating processes.
      • There's only one link between each pair of communicating processes.
      • Links can be unidirectional, but are typically bidirectional.

    Indirect Communication

    • Indirect communication uses mailboxes (or ports) to direct messages.
    • Each mailbox requires a unique identifier.
    • Processes can communicate with each other only if they share a common mailbox (port).
    • Properties of Indirect Communication:
      • Links are only established when processes share a mailbox.
      • Many processes can be connected to a single link.
      • Multiple communication links can exist between each pair of processes.
      • Links can be unidirectional or bidirectional.

    Indirect Communication

    • The operations for indirect communication include:
      • Create a new mailbox (port).
      • Send and receive messages through the mailbox.
      • Destroy the mailbox.
    • The primitives for indirect communication are:
      • send(A, message) – send a message to mailbox A.
      • receive(A, message) – receive a message from mailbox A.

    Indirect Communication

    • Mailbox sharing:
      • Multiple processes (for example, P1, P2, and P3) can share the same mailbox (for example, A).
      • One process might send a message to the mailbox, while other processes receive messages from the mailbox.
      • The question of which of the receiving processes will receive the message has 3 different implementations:
        • Zero capacity: No messages can be stored in the link, the sender must wait for the receiver (rendezvous).
        • Bounded capacity: The link can store a finite number of messages. The sender must wait if the link is full.
        • Unbounded capacity: The link has an infinite capacity, so the sender never has to wait.

    Examples of IPC Systems - POSIX

    • POSIX uses shared memory for interprocess communication.
    • A process uses shm_open to create or open a shared memory segment.
    • The ftruncate system call sets the size of the shared memory segment.
    • The process can write to the shared memory segment once the segment has been created.

    Examples of IPC Systems - Mach

    • Mach uses a message-based communication model for system calls.
    • All tasks (processes) receive two mailboxes when they are created: Kernel and Notify.
    • These tasks require only three system calls for message transfer:
      • msg_send()
      • msg_receive()
      • msg_rpc()
    • Mailboxes that are needed for communication are created through the port_allocate() system call.
    • The send and receive functions allow for flexible options, including:
      • Wait indefinitely.
      • Wait for a specific number of milliseconds.
      • Return immediately.
      • Cache a message temporarily.

    Examples of IPC Systems – Windows

    • Windows uses a message-passing based interprocess communication (IPC) model, specifically through the Advanced Local Procedure Call (LPC) facility.
    • LPC functions by establishing communication channels through ports.
    • The process initiating communication opens a handle to the subsystem’s connection port object.

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    Chapter 3: Processes PDF

    Description

    This quiz covers essential concepts in operating system process management, including termination methods, the role of parent and child processes, and the unique multiprocess architecture of Google Chrome. Test your understanding of process termination, zombie processes, and orphan processes.

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