Podcast
Questions and Answers
How many instances of resource type R3 are there?
How many instances of resource type R3 are there?
- 2
- 1 (correct)
- 3
- 0
Process P2 is waiting for an instance of resource type R4.
Process P2 is waiting for an instance of resource type R4.
False (B)
What resource is Process P3 holding?
What resource is Process P3 holding?
R3
Process P1 is holding an instance of R2 and waiting for an instance of _____
Process P1 is holding an instance of R2 and waiting for an instance of _____
Match the following processes with their statuses:
Match the following processes with their statuses:
What is a deadlock in an operating system?
What is a deadlock in an operating system?
In a deadlock, at least one resource must be held by a process that is not waiting.
In a deadlock, at least one resource must be held by a process that is not waiting.
What does RAG stand for in the context of resource allocation?
What does RAG stand for in the context of resource allocation?
A deadlock occurs when each process is waiting for a resource that is held by _______.
A deadlock occurs when each process is waiting for a resource that is held by _______.
In a Resource Allocation Graph (RAG), what does the notation 'P R' represent?
In a Resource Allocation Graph (RAG), what does the notation 'P R' represent?
Match the following processes with their states:
Match the following processes with their states:
The Resource Allocation Graph provides complete information about all processes and resources in a system.
The Resource Allocation Graph provides complete information about all processes and resources in a system.
What is the significance of the directed arrow in a Resource Allocation Graph?
What is the significance of the directed arrow in a Resource Allocation Graph?
Flashcards
Resource Instance
Resource Instance
A specific and available copy of a resource type.
Process State
Process State
The current status of a process in terms of holding resources and waiting for others.
Resource Type
Resource Type
A category of resources, like printers or desks.
Safe State (system)
Safe State (system)
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Deadlock
Deadlock
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Deadlock
Deadlock
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Resource Allocation Graph (RAG)
Resource Allocation Graph (RAG)
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Process
Process
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Resource
Resource
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Waiting/Request Edge
Waiting/Request Edge
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Holding/Assignment Edge
Holding/Assignment Edge
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Resource Instance
Resource Instance
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Deadlock Prevention
Deadlock Prevention
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Study Notes
Deadlock in Operating Systems
- Deadlock is a situation where each computer process waits for a resource assigned to another process. No process gets executed due to resource dependency.
Resource Allocation Graph (RAG)
- RAG visually represents the system's state.
- It details all processes holding or waiting for resources.
- It includes information about the available or used resources by processes.
RAG Components
- P: Represents a process.
- R: Represents resources.
- Filled Square: Denotes resources.
- Filled Circle: Denotes process instances.
- Filled Circle inside a square: Denotes the number of instances.
- P—>R: Waiting/request edge.
- R—>P: Holding/assignment edge.
Creating a RAG
- RAG Situation: Define processes (P) and resources (R) along with the relationship between them using edges (E).
- Resource Instances: Determine the number of each resource type (e.g., R1, R2).
- Process States: Detail the processes (e.g., P1, P2) and resource instances they currently hold or are waiting for
- Examples of RAG Situations provided include Example 1, Example 2, and Example 3.
Deadlock Avoidance
- To avoid deadlock, guarantee the system is in a safe state.
- A safe state allows resource allocation such that a safe sequence of processes exists.
- In an unsafe state, deadlock can potentially occur.
Safe vs. Unsafe States
- Examples for safe and unsafe states (Example 1, Example 2, and Example 3) illustrate how the maximum, current, and needed resources of processes determine the system's safety. Resource allocation needs are calculated to determine the system's safety.
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