Deadlock _ AI Flashcards by Wl hoe

Q

What is a deadlock?

A

Threads waiting for each other’s resources

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Q

Impact of deadlock?

A

Concurrent processes cannot complete

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Q

Methods to handle deadlocks?

A

Prevention, avoidance, detection, recovery

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Q

System resources consist of?

A

Finite resources among competing threads

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Q

Resource request sequence?

A

Request → Use → Release

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Q

Resource request via?

A

System calls (e.g., open/close)

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Q

Example deadlock problem?

A

Dining philosophers

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Q

Common sync tools?

A

Mutex locks and semaphores

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Q

Mutual exclusion?

A

Resource non-sharable

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Q

Hold and wait?

A

Holding and waiting for resources

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Q

No pre-emption?

A

Resources released voluntarily

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Q

Circular wait?

A

Cycle of threads waiting

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Q

How many conditions for deadlock?

A

All four must hold

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Q

Resource-allocation graph?

A

Directed graph of threads/resources

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Q

Request edge?

A

Thread → Resource request

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Q

Assignment edge?

A

Resource → Thread allocated

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Q

Threads shown as?

Study These Flashcards

A

Circles

Q

Resources shown as?

Study These Flashcards

A

Rectangles with instance dots

Q

No cycle implies?

Study These Flashcards

A

No deadlock

Q

Cycle implies deadlock when?

Study These Flashcards

A

Single instance per resource

Q

Cycle with multiple instances?

Study These Flashcards

A

Deadlock may not occur

Q

Three main approaches?

Study These Flashcards

A

Ignore, prevent/avoid, detect/recover

Q

Ignoring deadlocks cost?

Study These Flashcards

A

Cheaper, dev-managed

Q

Goal of prevention?

Study These Flashcards

A

Prevent a necessary condition

Prevention method?

Constrain request order

Avoidance requires?

Advance resource usage info

Avoidance decision based on?

Available, allocated, future requests

Avoidance side effect?

Low utilization

Detection graph variant?

Wait-for graph

Wait-for graph edge?

Thread→Thread wait

Detection overhead?

Runtime cost, recovery losses

Break deadlock methods?

Abort threads or preempt resources

Recovery option 1?

Abort all deadlocked processes

Recovery option 2?

Abort one process at a time

Reclaim resources from?

Terminated processes

Define system model importance?

Shows resource allocations

Primary deadlock methods?

Prevention, avoidance, detection, recovery

Prevention vs avoidance?

Limits requests vs uses info

Recovery methods?

Abort or preempt

List main topics?

Model, characterization, handling methods