Deadlock

Question 1

Try to explain deadlock in a sentence

Answer 1

Where process A has resource A, wants resource B.
A goes into waiting.
Process B has resource B. It wants resource B.
B goes into waiting.
Nothing escapes = deadlock

Question 2

What are the four conditions for deadlock

Answer 2

Mutual exclusion
No preemption
Hold and wait
Circular wait

Question 3

Explain mutual exclusion in relation to deadlock

Answer 3

a singular resource is currently held by one process

Question 4

Explain hold and wait in relation to deadlock

Answer 4

a process or process currently holding resources can ask for more resources

Question 5

Explain ‘no preemption’ in relation to deadlock

Answer 5

once a process holds a resource, this cannot be taken away from it

Question 6

Explain ‘circular wait’ in relation to deadlock

Answer 6

each process is waiting to get access to a resource held by another process

Question 7

Name the three ways typically used to handle deadlock

Answer 7

Ignoring it (ostrich)
Detection and recovery
Dynamic allocation of resources

Question 8

Why is dynamic allocation of resources problematic

Answer 8

You have to be able to preempt resources for a process. Once a human touches it = you’re fucked.

Question 9

Once deadlock has occurred, what are the four things you can do?

Answer 9

Abort everything
Backup processes to a checkpoint
Abort processes and restart them again

Question 10

What are the four things associated with critical regions and deadlock prevention to be mindful of

Answer 10

No two processes can enter a critical region = can’t request resources
No assumptions made about speed
No process outside critical region can interript something inside a critical region
Fairness still important, though, for scheduling.