Explain Busy Waiting Semaphores

Weak, Busy-wait Semaphores

a) The simplest way to implement semaphores.

b) Useful while critical sections last for a short time, or we comprise lots of CPUs.

c) S initialized to positive value (to permit someone in at the beginning).

d) S is an integer variable that, aside from initialization, can only be accessed by 2 atomic and mutually exclusive operations: 

wait(s):

while (s.value != 0);

s.value--;

signal(s):

s.value++;

 All happens atomically that is wrap pre and post protocols.