Deadlocks

Question 1

What is a deadlock?

Answer 1

A permanent blocking of a set of processes that are competing for resources

Question 2

How do deadlocks occur?

Answer 2

1. When 2 processes request the same resource that can’t be run twice at the same time
2. When there is limited memory available and a process tries to request more memory than is available

Question 3

What are the preconditions that will lead to a deadlock?

Answer 3

Mutual exclusion - only one process can use a resource at a time

Hold-and-wait - a process can hold resources while it is waiting for other resources to become available

Question 4

What is a condition that will lead to a deadlock?

Answer 4

Circular wait - Processes wait for each other to release resources they want to acquire, they form a kind of “closed chain of processes”

Question 5

How to handle deadlocks with deadlock prevention?

Answer 5

Avoid at least 1 of the 4 deadlock conditions

Question 6

How to handle deadlocks with deadlock avoidance?

Answer 6

Resources are reserved in a way so they do not lead to a deadlock

Question 7

How to handle deadlocks with deadlock detection?

Answer 7

1. There is no restriction on resource allocation
2. There is a periodic check to see if a deadlock is occurring
3. In case a deadlock is detected, recovery mechanisms are employed