19. Mutual Exclusion

Question 1

Race Condition

Answer 1

• An uncontrolled access by two or more concurrent processes to a shared variable where the final state of the data depends on the interleaving of instructions

Question 2

Critical Section

Answer 2

• The part of the code that changes the state of a shared resource

Question 3

Mutual Exclusion

Answer 3

• At most one process can be in the critical section of the code

Question 4

Isolation

Answer 4

• Processes not in the critical section nor trying to get into the critical section should not participate in the protocol used to guarantee mutual exclusion and should not be affected by it

Question 5

Progress

Answer 5

• The decision of which process may access the critical section cannot be postponed indefinitely

Question 6

Bounded Waiting

Answer 6

• After a process has made a request to enter its critical section, there is a bound on the number of times that other processes are allowed to enter their critical sections

Question 7

Flaw of Hardware Solution for Mutual Exclusion

Answer 7

• Not possible in multi-processing environments
• Violates isolation and bounded waiting in uni-processing environments

Question 8

Flaw of Taking Strict Turns

Answer 8

• Violates isolation

Question 9

Flaw of Signal Use of Critical Section

Answer 9

• Violates mutual exclusion due to a race condition

Question 10

Flaw of Signal Intention to Use Critical Section

Answer 10

• Can lead to livelock

Question 11

Flaw of Intermittently Signal Intention to Use Critical Section

Answer 11

• Can lead to livelock