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Deadlock can occur when two processes hold resources and wait for each other to release them.
Deadlock can occur when two processes hold resources and wait for each other to release them.
True
In a deadlock situation, all processes can continue to execute without any intervention.
In a deadlock situation, all processes can continue to execute without any intervention.
False
A gridlock alert in New York is similar to a deadlock in operating systems.
A gridlock alert in New York is similar to a deadlock in operating systems.
True
Process A holding Drive B while waiting for Drive A to continue is an example of deadlock.
Process A holding Drive B while waiting for Drive A to continue is an example of deadlock.
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Deadlock can be resolved by unplugging the computer.
Deadlock can be resolved by unplugging the computer.
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Resource allocation is irrelevant in the context of deadlock.
Resource allocation is irrelevant in the context of deadlock.
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In the given example, Process A and Process B are both trying to copy files simultaneously from the same drives.
In the given example, Process A and Process B are both trying to copy files simultaneously from the same drives.
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The presence of two processes each waiting for a resource held by the other can lead to a deadlock condition.
The presence of two processes each waiting for a resource held by the other can lead to a deadlock condition.
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Process P2 has a need of 6 instances of resource A.
Process P2 has a need of 6 instances of resource A.
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The total number of instances of resource B that process P4 needs is 3.
The total number of instances of resource B that process P4 needs is 3.
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The available resources for type C are calculated as 2 instances.
The available resources for type C are calculated as 2 instances.
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Process P1 is allocated 2 instances of resource C.
Process P1 is allocated 2 instances of resource C.
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The calculated need for resource B for process P3 is 1 instance.
The calculated need for resource B for process P3 is 1 instance.
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Eliminating mutual exclusion can be achieved solely through software solutions.
Eliminating mutual exclusion can be achieved solely through software solutions.
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Preventing hold and wait requires that processes must necessarily surrender their held resources before requesting new ones.
Preventing hold and wait requires that processes must necessarily surrender their held resources before requesting new ones.
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Requiring processes to request all needed resources before execution can lead to high resource utilization.
Requiring processes to request all needed resources before execution can lead to high resource utilization.
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Circular waiting can be eliminated by enforcing a specific order for resource allocation.
Circular waiting can be eliminated by enforcing a specific order for resource allocation.
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Starvation may occur when resources are held for long periods without being utilized.
Starvation may occur when resources are held for long periods without being utilized.
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A process can hold multiple resources indefinitely while waiting for others under all conditions.
A process can hold multiple resources indefinitely while waiting for others under all conditions.
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Eliminating hold and wait does not affect the overall efficiency of a system.
Eliminating hold and wait does not affect the overall efficiency of a system.
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Processes must wait indefinitely if they do not hold any resources at the time of requesting new ones.
Processes must wait indefinitely if they do not hold any resources at the time of requesting new ones.
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P0's request for 2 B's is more than the available resources.
P0's request for 2 B's is more than the available resources.
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The allocation changes for P0 after requesting 2 B's.
The allocation changes for P0 after requesting 2 B's.
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P0's need for resources is increased after the allocation of 2 B's.
P0's need for resources is increased after the allocation of 2 B's.
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After P0's request, the state remains safe.
After P0's request, the state remains safe.
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The process P1 has a maximum need of 2 resources of type B.
The process P1 has a maximum need of 2 resources of type B.
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Adding 2 B's to P0's allocation makes it impossible to meet the needs of other processes.
Adding 2 B's to P0's allocation makes it impossible to meet the needs of other processes.
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The total number of resources of type C available is 1 after processing P0's request.
The total number of resources of type C available is 1 after processing P0's request.
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The work vector reflects the total available resources after P0's allocation.
The work vector reflects the total available resources after P0's allocation.
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Only one process can read from a keyboard at a time.
Only one process can read from a keyboard at a time.
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Hold and wait means that a process cannot hold onto a resource while waiting for another.
Hold and wait means that a process cannot hold onto a resource while waiting for another.
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Circular waiting involves a scenario where process A is waiting for process B, which is waiting for process C, and C is waiting for A.
Circular waiting involves a scenario where process A is waiting for process B, which is waiting for process C, and C is waiting for A.
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Mutual exclusion allows multiple processes to hold the same resource simultaneously.
Mutual exclusion allows multiple processes to hold the same resource simultaneously.
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In a resource-allocation graph, an arrow pointing from a resource to a process indicates that the process is holding the resource.
In a resource-allocation graph, an arrow pointing from a resource to a process indicates that the process is holding the resource.
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A circuit in a resource-allocation graph guarantees that a deadlock will occur.
A circuit in a resource-allocation graph guarantees that a deadlock will occur.
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The statement '5 chairs, no waiting' implies that at most 5 customers can be served at the same time.
The statement '5 chairs, no waiting' implies that at most 5 customers can be served at the same time.
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No preemption means that a resource can be taken from a process forcefully at any time.
No preemption means that a resource can be taken from a process forcefully at any time.
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A system without deadlock avoidance must implement algorithms for deadlock detection and deadlock recovery.
A system without deadlock avoidance must implement algorithms for deadlock detection and deadlock recovery.
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In the case of single-instance resource allocation, a graphical approach can be used to detect deadlock.
In the case of single-instance resource allocation, a graphical approach can be used to detect deadlock.
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All processes in a deadlock situation are waiting for resources they currently hold.
All processes in a deadlock situation are waiting for resources they currently hold.
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The allocation graph can indicate deadlocks by showing circuits among processes and resources.
The allocation graph can indicate deadlocks by showing circuits among processes and resources.
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Work and Finish vectors are used in the deadlock detection algorithm when there are multiple instances of each resource.
Work and Finish vectors are used in the deadlock detection algorithm when there are multiple instances of each resource.
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Redrawing the request edges in a resource allocation graph makes it harder to identify which process is waiting for a resource.
Redrawing the request edges in a resource allocation graph makes it harder to identify which process is waiting for a resource.
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Deadlock recovery does not require a separate algorithm if deadlock detection is implemented.
Deadlock recovery does not require a separate algorithm if deadlock detection is implemented.
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If all processes in the system have a Finish status of True, then deadlock is guaranteed to be present.
If all processes in the system have a Finish status of True, then deadlock is guaranteed to be present.
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Study Notes
Deadlock in Operating Systems
- Deadlock occurs when two or more processes are blocked indefinitely, waiting for each other to release resources.
- This is a critical issue in operating systems, impacting efficiency and causing system instability.
- Gridlock in traffic is a real-world analogy. Cars are stuck in an intersection, blocking cross-traffic paths. This creates a system-wide blockage.
Necessary Conditions for Deadlock
- Mutual Exclusion: A resource can be used 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 can't be forcibly taken away from a process holding it; the process must voluntarily release it.
- Circular Wait: There exists a circular chain of two or more processes, where each process is waiting for a resource held by the next process in the chain.
How Deadlock Occurs
- Processes effectively block each other.
- Each process is holding something that the other process wants.
- Neither process can move forward.
Example of Deadlock
- Process A: Copies a file from drive A to drive B, holding drive A and waiting for drive B.
- Process B: Copies a file from drive B to drive A, holding drive B and waiting for drive A.
- Both processes are blocked, waiting for the other to release a necessary resource (the drive).
Resource Allocation Graph
- Resource allocation graph helps visualize the problem.
- Green circles represent resources.
- Blue rectangles represent processes.
- An arrow from a resource to a process means the process holds the resource.
- An arrow from a process to a resource means the process is waiting for that resource.
- A cycle in the graph indicates a potential deadlock.
Deadlock Prevention
- Eliminating Mutual Exclusion: (Rarely Possible) Not suitable for most shared resources.
- Eliminating Hold and Wait: Request all needed resources before starting. Request resources before releasing others or a process is unable to request resources if it's already holding any (if possible).
- Eliminating No Preemption: Allow OS to preempt resources of a process waiting for another resource. A process that is holding resources must give up all the acquired resources.
- Eliminating Circular Wait: Require resources have a strict ordering for request .
Deadlock Avoidance
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Safe State: The system can allocate resources to processes in some order such that no deadlock will occur.
-
Unsafe State: The system might enter a state from which deadlock is possible.
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Operating system prevention and system throughput get reduced.
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Operating system manages resource requests.
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Determines whether or not requests can be fulfilled without risk of a deadlock.
Banker's Algorithm
- Useful approach to avoid deadlock.
- OS checks for the safety of granting all requests.
- Checks if granting the resource and releasing it will lead to a safe state.
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Description
This quiz explores the concept of deadlock in operating systems, detailing its definition, conditions, and implications. Understand how processes can become indefinitely blocked and the necessary conditions that lead to such scenarios. Learn about the real-world analogies that help clarify this critical issue.
