Operating Systems - Chapter 5: Deadlocks
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Questions and Answers

Which of the following is NOT a condition for deadlock to occur?

  • Resource sharing (correct)
  • Hold and wait
  • Mutual exclusion
  • Circular wait

    • The hold and wait condition states that processes can hold resources while waiting for more resources.

    True

    What occurs in a deadlock state?

    Every process is waiting for a resource held by another process in the set.

    Circular wait means there exists a set {P0, P1, …, Pn} of waiting processes such that each process is waiting for a resource held by the next process in the set, with the last process waiting for __________.

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

    Match the terms with their definitions:

    <p>Mutual exclusion = Only one process can use a resource at a time No preemption = A resource may only be released voluntarily Hold and wait = A process holding resources is waiting for more Circular wait = A circular chain of processes waiting for resources</p> Signup and view all the answers

    In a resource-allocation graph, what do the vertices represent?

    <p>Both processes and resources</p> Signup and view all the answers

    A resource can be preempted from a process if necessary.

    <p>False</p> Signup and view all the answers

    What resource types can be classified as physical resources?

    <p>Printers, DVD drives, memory space, and CPU cycles.</p> Signup and view all the answers

    What protocol requires a process to request resources in increasing order based on their enumeration?

    <p>Protocol#1</p> Signup and view all the answers

    A process can request any resource type without restrictions according to the deadlock prevention protocols.

    <p>False</p> Signup and view all the answers

    If a process requests a disk drive first, which resources can it request next according to the protocols?

    <p>Only resources that have a higher function value than the disk drive.</p> Signup and view all the answers

    What situation is described as a deadlock?

    <p>A set of blocked processes each holding a resource and waiting for another.</p> Signup and view all the answers

    In the function F defined for resource types, F(tape drive) is equal to ______.

    <p>1</p> Signup and view all the answers

    Match the following resource types with their corresponding function values:

    <p>Tape drive = 1 Disk drive = 5 Printer = 12 Scanner = Not defined</p> Signup and view all the answers

    Most operating systems actively prevent deadlocks.

    <p>False</p> Signup and view all the answers

    In a multiprogramming environment, what happens to a process that requests resources that are not available?

    <p>The process enters a waiting state.</p> Signup and view all the answers

    A process must request a resource before using it and must __________ the resource after using it.

    <p>release</p> Signup and view all the answers

    In the bridge crossing example, what is one potential solution to a deadlock?

    <p>One car backs up, preempting resources.</p> Signup and view all the answers

    If a system has two CPUs, then the resource type __________ has two instances.

    <p>CPU</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Deadlock = A situation where processes are blocked, waiting on each other. Resource = An element that processes require to perform tasks. Starvation = A situation where a process is perpetually denied necessary resources. Multiprogramming = Running multiple processes concurrently to maximize resource utilization.</p> Signup and view all the answers

    What is meant by 'starvation' in the context of deadlocks?

    <p>Starvation refers to a situation where a process is indefinitely denied resources it needs.</p> Signup and view all the answers

    Which condition is NOT required for sharable resources in deadlock prevention?

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

    Hold and Wait condition ensures that processes must hold at least one resource while requesting additional resources.

    <p>False</p> Signup and view all the answers

    What is one potential problem that can arise from the No Preemption policy in deadlock prevention?

    <p>Starvation</p> Signup and view all the answers

    To prevent deadlock, the ___ resource must be non-sharable.

    <p>non-sharable</p> Signup and view all the answers

    Match the deadlock prevention condition to its description:

    <p>Mutual Exclusion = At least one resource must be non-sharable Hold and Wait = Processes cannot hold resources while requesting others No Preemption = Resources held can be released if a request cannot be satisfied Circular Wait = Imposing a total ordering of resources</p> Signup and view all the answers

    What is a major advantage of applying the No Preemption policy?

    <p>Improves resource utilization</p> Signup and view all the answers

    All resource types can be preempted to prevent deadlock.

    <p>False</p> Signup and view all the answers

    What strategy can be employed to prevent the Circular Wait condition?

    <p>Impose a total ordering of resources</p> Signup and view all the answers

    What type of edge represents a request from a process to a resource in a Resource Allocation Graph?

    <p>Request edge</p> Signup and view all the answers

    If a Resource Allocation Graph contains no cycles, it indicates that a deadlock may occur.

    <p>False</p> Signup and view all the answers

    What happens if a Resource Allocation Graph contains a cycle and there is only one instance per resource type?

    <p>There is a deadlock.</p> Signup and view all the answers

    A process represented by Pi that holds an instance of Rj is indicated by the edge _____ Rj.

    <p>Pi →</p> Signup and view all the answers

    Match the following processes with their resource states:

    <p>P1 = Holding R2, waiting for R1 P2 = Holding R1 and R2, waiting for R3 P3 = Holding R3, not waiting</p> Signup and view all the answers

    Which of the following represents a directed edge indicating that a resource has been allocated to a process?

    <p>Rj → Pi</p> Signup and view all the answers

    In a Resource Allocation Graph, a cycle that is not breakable means a deadlock is guaranteed.

    <p>True</p> Signup and view all the answers

    List the resource types in the example given in the Resource Allocation Graph.

    <p>R1, R2, R3, R4</p> Signup and view all the answers

    What indicates the presence of deadlock in a resource allocation graph?

    <p>The presence of cycles</p> Signup and view all the answers

    If a resource allocation graph contains no cycles, a deadlock exists.

    <p>False</p> Signup and view all the answers

    What are the three methods that an operating system can use to handle deadlocks?

    <p>Prevent, Detect &amp; Recover, Ignore</p> Signup and view all the answers

    Deadlock _____ prevents the necessary conditions for deadlock from occurring.

    <p>prevention</p> Signup and view all the answers

    Match the following methods for handling deadlocks with their descriptions:

    <p>Preventing Deadlocks = Ensures system never enters a deadlocked state Detecting Deadlocks = Allows the system to identify and recover from a deadlock Ignoring Deadlocks = Pretends that deadlocks do not occur</p> Signup and view all the answers

    How does deadlock avoidance differ from deadlock prevention?

    <p>Deadlock avoidance requires advance information about resource requests</p> Signup and view all the answers

    In a deadlock situation, at least one process must be able to release its resources.

    <p>False</p> Signup and view all the answers

    Describe what happens in Example (2) of the Resource Allocation Graph.

    <p>There are two cycles leading to a deadlock situation.</p> Signup and view all the answers

    Study Notes

    Operating Systems - CS 340

    • This course covers Operating Systems, specifically chapter 5 on Deadlocks.
    • Deadlocks occur when processes are stuck waiting for resources, which are held by other waiting processes. This prevents the processes from completing.

    Chapter 5: Deadlocks

    • The chapter covers the deadlock problem, methods for deadlock characterization, and methods for managing deadlocks.
    • The material is in the 7th chapter of the textbook.

    Deadlock Problem

    • In a multitasking environment, multiple processes contend for a limited number of resources.
    • If a process requests resources, temporarily unavailable, it will enter a waiting state.
    • Sometimes, waiting processes can't resume because the resources they need are held by other still-waiting processes. This is a deadlock.

    Deadlock Characterization

    • Deadlocks occur when four conditions are simultaneously present in the system.
      • Mutual exclusion: only one process can use a resource at a time,
      • Hold and wait: a process is holding at least one resource and waiting for others,
      • No preemption: a resource held by a process cannot be forcibly taken away.
      • Circular wait: a set of processes wait in a circular chain, each waiting for a resource held by the next process in the chain.

    Resource Allocation Graph

    • Deadlocks can be visually represented using resource allocation graphs.
      • Processes are represented by circles (nodes).
      • Resources are represented by squares (nodes).
      • Directed edges depict requests and assignments.
      • A cycle in the graph signifies a potential deadlock, especially when cycle is NOT breakable.

    Methods for Handling Deadlocks

    • Operating Systems can deal with the deadlock problem in three ways:

      • Prevention: Designing the system to prevent deadlocks from ever occurring. Strategies include:

        • Avoid Mutual Exclusion: allowing multiple processes to access resources at once for sharable resources
        • No Hold and Wait: Processes must request all resources before starting.
        • No Preemption: Resources can be forcibly taken from a waiting process to be allocated to other waiting processes.
        • Avoid Circular Wait: order resources and processes must acquire in increasing order.

      • Detection: Allow the system to enter a deadlocked state, then detect the condition and recover from it.

      • Avoidance: Prevent deadlocks by carefully selecting the order in which processes request resources.

        • A process that requests a resource must know how many units it needs in advance.

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    Description

    This quiz covers chapter 5 of the Operating Systems course, focusing on the concept of deadlocks. Understand the conditions leading to deadlocks, characterization methods, and management strategies. Test your knowledge on how processes interact in a multitasking environment and the risks of resource contention.

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