9 - Dining Philosophers, Locks, Mutexes

Question 1

What is Deadlock?

Answer 1

A state in which each member of a group is waiting for another member, including itself, to take action, such as sending a message or more commonly releasing a lock.

Question 2

What is Livelock?

Answer 2

States of the processes involved in the livelock constantly change with regard to one another, none progressing.

Question 3

What is the Arbitrator Solution?

Answer 3

One thread gets to go at a time.

Non-optimal use of resources

Question 4

What is the Random Timeout Solution?

Answer 4

If resources are not availible, thread takes a short RANDOM sleep.
A small (likely non-permanent) chance of starvation.

Question 5

What is the Resource Hierarchy Solution?

Answer 5

Establishes a partial order on resources

Question 6

What is a Mutex?

Answer 6

Mutex = Mutual Exclusion

A synchronization mechanism used for ensuring exclusive access to a resource in concurrent programs.

Question 7

What is Unfairness?

Answer 7

Not all processes get equal opportunity to progress

Question 8

Name/explain two general approaches for cancelling a thread.

Answer 8

Asynchronous
 - pthread_kill()
Deferred / Synchronous
 - Setting some shared global flag
 - pthread_cancel()

Question 9

Are signals handled per thread or per process?

Answer 9

Per process

Question 10

Race Conditions are not a problem among processes, only threads.
True or False?

Answer 10

False

Question 11

A mutex has only two states: Locked and unlocked.

True or False?

Answer 11

True