Concurrency

Question 1

Atomic Operation

Answer 1

A function or action that cannot be interrupted under any circumstances

Question 2

Critical Section

Answer 2

A section of code with shared resources that cannot be executed when another process is using the shared resources

Question 3

Deadlock

Answer 3

When 2 or more processes cannot run as they are waiting for each other to run

Question 4

Livelock

Answer 4

When 2 or more processes continuously change their state in response to the other processes, without doing any meaningful work

Question 5

Mutual Exclusion

Answer 5

The requirement that only one process can have access to shared resources at at time

Question 6

Race Condition

Answer 6

Multiple processes access a shared data file and the final result depends on the timing of the process

Question 7

Starvation

Answer 7

A process is overlooked indefinitely by the scheduler, it is ready to run but is never run

Question 8

How to prevent race conditions?

Answer 8

Create critical sections with mutual exclusion. Processes can only access shared resources after another process has finished accessing the same resources

Question 9

Problem with mutual exclusion?

Answer 9

Enforcing mutual exclusions creates deadlocks and starvation

Question 10

Solutions to critical section problem?

Answer 10

Software Solution - shared lock variables, busy waiting
Hardware Solution - disabling interrupts, special instructions
Higher Level OS Constructs - semaphores, monitors, message passing

Question 11

Shared lock problem

Answer 11

The lock itself is a shared variable so it is possible 2 processes could have a race condition on it