Introduction to Deadlock Concepts
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What is a deadlock situation in a computing environment?

  • A process executes without waiting for any resources
  • Resources are granted to processes in an arbitrary order
  • All processes are able to complete their execution
  • Processes are waiting for resources held by each other (correct)

    • What must a process do before using a resource?

  • Release any resources it currently holds
  • Start execution without requests
  • Request the resource (correct)
  • Wait for an indefinite time

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

  • Wait for a resource indefinitely (correct)
  • Circular wait
  • Mutual exclusion
  • No preemption

    • What is the first step a process takes to utilize a resource?

    <p>Request the resource from the operating system</p> Signup and view all the answers

    In a scenario where two processes are waiting on each other for resources, which prevention technique can help resolve this situation?

    <p>Implement resource preemption</p> Signup and view all the answers

    Which aspect of resource management can lead to deadlock avoidance?

    <p>Granting resources in a strict sequence dictated by priority</p> Signup and view all the answers

    How does a process operate on a resource after it has been granted?

    <p>By using the resource to complete its task</p> Signup and view all the answers

    What happens to a process if its resource request cannot be granted immediately?

    <p>The process waits until the resource is available</p> Signup and view all the answers

    What condition occurs when a process holds a resource while waiting for another resource?

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

    What is the Conservative approach in resource allocation?

    <p>Ensuring all necessary resources are available before execution starts</p> Signup and view all the answers

    What is one potential drawback of using the No Preemption condition?

    <p>It may lead to system starvation for some processes</p> Signup and view all the answers

    Which of the following methods can help prevent circular wait?

    <p>Prioritizing resources and limiting requests to increasing order</p> Signup and view all the answers

    What happens when a process requests additional resources while holding some?

    <p>All held resources are pre-empted</p> Signup and view all the answers

    Why is the Conservative approach considered inefficient?

    <p>Processes cannot determine their resource needs initially</p> Signup and view all the answers

    In a situation where pre-emption is allowed, what might be a worst-case scenario?

    <p>No process can complete due to resource pre-emption</p> Signup and view all the answers

    Which of the following conditions must be satisfied for a deadlock to potentially occur?

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

    What is a characteristic of the Hold and Wait condition?

    <p>Processes hold resources while waiting for others</p> Signup and view all the answers

    What does the condition 'Hold and Wait' imply in the context of deadlocks?

    <p>A process can hold multiple resources while requesting additional resources.</p> Signup and view all the answers

    Which of the following statements best describes 'No Preemption' in deadlock scenarios?

    <p>Resources can only be released by processes voluntarily.</p> Signup and view all the answers

    In a situation where processes engage in circular waiting, what is likely to happen?

    <p>All involved processes will remain in a waiting state, leading to deadlock.</p> Signup and view all the answers

    If all four conditions necessary for a deadlock are fulfilled, what can be concluded?

    <p>A deadlock may or may not happen.</p> Signup and view all the answers

    Which scenario exemplifies the condition of 'Circular Wait'?

    <p>Process 3 is requesting Resource 1 held by Process 1, which is waiting for Resource 2 held by Process 2.</p> Signup and view all the answers

    What does Mutual Exclusion ensure in the context of resource allocation?

    <p>That only one process can hold a specific resource at any time.</p> Signup and view all the answers

    Which statement best embodies the concept of 'Hold and Wait'?

    <p>Processes can wait for more resources while retaining those currently held.</p> Signup and view all the answers

    What is the primary goal of deadlock avoidance?

    <p>To grant resource requests only if the resulting state is safe</p> Signup and view all the answers

    Which algorithm is associated with deadlock avoidance?

    <p>Banker's Algorithm</p> Signup and view all the answers

    What defines a safe state in a system?

    <p>A state where all processes can finish in some order</p> Signup and view all the answers

    In the context of Banker's Algorithm, what does the Need matrix represent?

    <p>Resources still needed by each process to complete</p> Signup and view all the answers

    What happens in an unsafe state regarding deadlock?

    <p>The state may lead to deadlock if resources are requested</p> Signup and view all the answers

    When a process requests resources in the Resource-Request Algorithm, what is the first course of action?

    <p>Check if the request can result in a safe state</p> Signup and view all the answers

    Which of the following best describes a deadlock?

    <p>A state where processes are waiting indefinitely for resources</p> Signup and view all the answers

    In the context of resource allocation, which resource would be prioritized in a safe state?

    <p>Resources that can be allocated to allow all processes to finish</p> Signup and view all the answers

    What is the primary objective of deadlock prevention?

    <p>To ensure deadlock will never occur</p> Signup and view all the answers

    Which condition is essential for a deadlock to occur?

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

    What defines deadlock avoidance in operating systems?

    <p>Using a data set to ensure a safe state before granting requests</p> Signup and view all the answers

    Which of the following can help prevent deadlock through resource sharing?

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

    What happens during deadlock detection and recovery?

    <p>Deadlock occurs and is detected for recovery</p> Signup and view all the answers

    Which technique allows a process to continue working without waiting for a dedicated resource like a printer?

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

    What must be violated to effectuate deadlock prevention?

    <p>At least one of the four necessary conditions</p> Signup and view all the answers

    Which of the following is NOT a condition necessary for a deadlock?

    <p>Resource sharing</p> Signup and view all the answers

    Study Notes

    Introduction to Deadlock

    • Deadlock is a situation where each computer process waits for a resource assigned to another process.
    • In this scenario, no process executes, as each waits for a resource held by another waiting process.
    • A deadlock creates an impasse, as resources are held by processes which are blocked, waiting for other resources

    System Model

    • A system has a finite number of resources allocated among multiple competing processes.
    • Resources can be categorized into various types.
    • Each resource type has multiple instances (e.g., printers, DVD drives, CPUs).
    • A process must request a resource before using it and release it afterwards.
    • A process can request multiple resources to perform its task.
    • The number of resources requested doesn't exceed the total available resources.

    Deadlock Sequence

    • Processes request a resource
    • If available, the OS grants the resource; otherwise, the process waits.
    • The process uses the resource and releases it upon completion.

    Necessary Conditions for Deadlock

    • Mutual Exclusion: A resource can be held by only one process at a time.
    • Hold and Wait: A process holding at least one resource is waiting to acquire additional resources held by other processes.
    • No Preemption: A resource cannot be forcibly taken away from a process holding it; it can only be released voluntarily.
    • Circular Wait: A circular chain of two or more processes exists, where each process is waiting for a resource held by the next process in the chain.

    Strategies for Handling Deadlock

    • Deadlock Prevention: Designing a system to violate at least one of the four necessary conditions for deadlock to prevent it from occurring.
    • Deadlock Avoidance: Maintaining data about resource allocation to decide whether granting a resource request will lead to a safe state. Banker's Algorithm is an example.
    • Deadlock Detection and Recovery: Detecting deadlocks when they occur and recovering by taking actions such as process termination or resource preemption.

    Banker's Algorithm

    • The algorithm uses data structures (Available, Max, Allocation, Need) to analyze the state of the system.
    • A system state is safe if a sequence of processes can be found to complete without causing a deadlock.
    • If a request would lead to an unsafe state, the request is denied.
    • Safety algorithm is used to check for safe states.
    • Resource request algorithm allows for a resource to be granted, if a safe state is maintained.

    Recovery from Deadlock

    • Process Termination: Aborting one or more deadlocked processes to break the deadlock cycle. - Kill all deadlocked processes. - Kill one process at a time.
    • Resource Pre-emption: Taking a resource away from a process and giving it to another to break the cycle. - Selecting a victim: Determining which resource and process to preempt, based on cost factors. - Rollback: Rolling back the process to a previous safe state to restart it.
    • Starvation: Ensuring that a process is not repeatedly chosen as a victim to prevent it from never completing its assigned tasks.

    Deadlock vs Starvation

    • Deadlock occurs when multiple processes are blocked, and none can proceed. There is a circular wait.
    • Starvation happens when a process is repeatedly denied resources, preventing it from making progress. Limited resources may be continuously used by other, higher priority processes.

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    Related Documents

    OS Unit 3 - Deadlocks 2023 PDF

    Description

    Explore the fundamental concepts of deadlock in computer systems. This quiz covers the definition of deadlock, system model, and the sequence of events leading to deadlock situations. Understand how competing processes interact with resources and what causes them to reach an impasse.

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