Race conditions are not a problem if we only have a computer with a single CPU.

Allowing two or more threads to access a critical region at the same time is desirable.

A thread can only block other threads from a critical region once that thread is inside the critical region.

A race condition is when two or more threads are racing against each other and it is hard to predict the winner.

In concurrent programming, a critical region is a part of the program where time-critical (or safety-critical) operations take place.

If only one thread at a time can access a shared resource, we have enforced mutual exclusion.