Details about two algorithms below can be refered from slides by Prof. Gagan.

Lamport Algo.

FIFO: required
Lamport Clock: not

What’s the problem if FIFO is not satisfied?
Some thread could enter into critical section at the same time.

Ricart-Agrawala Algo.

FIFO: not required
Lamport Clock: required

What happens if the system violates the rule of Lamport Clock?
The critical section could be accessed by different threads simultaneously.