Operating Systems Chapter 6 Flashcards
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Questions and Answers

Give examples of reusable and consumable resources.

Examples of reusable resources are processors, I/O channels, main and secondary memory, devices, and data structures such as files, databases, and semaphores. Examples of consumable resources are interrupts, signals, messages, and information in I/O buffers.

What are the three conditions that must be present for deadlock to be possible?

Mutual exclusion, hold and wait, and no preemption.

What are the four conditions that create deadlock?

Mutual exclusion, hold and wait, no preemption, and circular wait.

How can the hold-and-wait condition be prevented?

<p>By requiring that a process request all of its required resources at one time and blocking the process until all requests can be granted simultaneously.</p> Signup and view all the answers

How can the circular wait condition be prevented?

<p>By defining a linear ordering of resource types.</p> Signup and view all the answers

What is the difference among deadlock avoidance, detection, and prevention?

<p>Deadlock prevention constrains resource requests to prevent one of the conditions of deadlock. Deadlock avoidance allows the conditions but makes judicious choices to ensure the deadlock point is never reached. Deadlock detection grants resources whenever possible and uses algorithms to detect circular wait.</p> Signup and view all the answers

Mutual exclusion allows multiple processes to use a resource at the same time.

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

Hold and wait means a process is waiting while holding at least one resource.

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

No preemption means resources can be forcibly taken from a process.

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

What does circular wait refer to?

<p>A closed chain of processes exists such that each process holds at least one resource needed by the next process in the chain.</p> Signup and view all the answers

What are the categories of reusable resources?

<p>Resources that can be safely used by only one process at a time and are not depleted by that use.</p> Signup and view all the answers

What defines consumable resources?

<p>Consumable resources are those that can be created and destroyed.</p> Signup and view all the answers

What is meant by a 'safe state'?

<p>A state in which there is at least one sequence of resource allocations to processes that does not result in a deadlock.</p> Signup and view all the answers

What is an 'unsafe state'?

<p>A state that is not safe.</p> Signup and view all the answers

Flashcards

Reusable Resource

A resource that can be used by multiple processes without being depleted.

Consumable Resource

A resource that is used up, consumed, or depleted in the process of being used.

Mutual Exclusion

Only one process can use a resource at once.

Hold and Wait

A process holding resources while waiting for more.

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No Preemption

Resources can't be taken away from a process once allocated.

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Circular Wait

Processes waiting for resources in a circle, each needing one held by the next.

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Deadlock Prevention (Hold-and-Wait)

Processes need to request all needed resources at once.

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Deadlock Prevention (Circular Wait)

Setting a linear order of resource types for processes.

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Deadlock Prevention

Techniques to prevent deadlock conditions by controlling resource requests.

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Deadlock Avoidance

Approaches that evaluate resource requests and decide whether to grant them to prevent deadlock.

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Deadlock Detection

Checking for circular dependencies and allowing resource requests to break cycles if found.

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Safe State

A state where there's a way to allocate resources to processes without deadlock.

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Unsafe State

A state where deadlock is possible during resource allocation.

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Deadlock Avoidance

Makes choices about allocating resources to avoid deadlock

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Study Notes

Resource Types

  • Reusable Resources: Include processors, I/O channels, main and secondary memory, devices, files, databases, and semaphores. They can be safely utilized by one process at a time and are not depleted with use.
  • Consumable Resources: Examples are interrupts, signals, messages, and I/O buffer information. These can be produced and consumed.

Deadlock Conditions

  • Mutual Exclusion: Only one process can use a resource at any given time.
  • Hold and Wait: A process may hold allocated resources while waiting for additional resources.
  • No Preemption: Resources cannot be forcibly taken from a process that is holding them.
  • Circular Wait: A closed loop of processes exists where each holds at least one resource needed by the next.

Deadlock Prevention and Avoidance

  • Preventing Hold-and-Wait: Processes must request all required resources simultaneously and are blocked until all requests can be granted.
  • Preventing Circular Wait: Define a linear ordering of resource types, allowing processes to request only those types that follow their already allocated resource.

Deadlock Management Strategies

  • Deadlock Prevention: Involves constraints on resource requests to eliminate at least one of the four necessary deadlock conditions.
  • Deadlock Avoidance: Allows the three necessary conditions but makes careful decisions to prevent reaching a deadlock state.
  • Deadlock Detection: Periodically checks for circular wait conditions and allows resource requests whenever possible under a detection algorithm.

Resource Allocation States

  • Safe State: A condition where there is at least one sequence of resource allocations to processes that avoids deadlock.
  • Unsafe State: A scenario without a guarantee of avoiding deadlock, indicating potential risk in resource allocation.

Key Definitions

  • Mutual Exclusion: Only one process can utilize a resource at a time.
  • Hold and Wait: A process is holding resources and waiting for others.
  • No Preemption: Resources cannot be preempted from any process holding them.
  • Circular Wait: Represents a situation where processes form a loop, each waiting on resources from others.

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Test your knowledge on Chapter 6 of Operating Systems with these flashcards. This chapter focuses on resource types and conditions for deadlock. Enhance your understanding through examples and key concepts presented in this quiz.

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