Question

Example of Race condition as given in operating System Concepts is

count++ could be implemented as 
register = count
register = register1 + 1
count = register1

count-- could be implemented as
register2 = count
register2 = register2 - 1
count = register

consider this execution interleaving

s0: producer execute register = count
s1: producer execute register1 = register1 + 1
s2: consumer execute register2 = count
s3: consumer execute register2 = register2 - 1
s4: producer execute count = register1
s5: consumer execute count = register2

How the interleaving of instructions is decided? is it random or some algorithm is used for it? and, who decideds it?

Answer 1

In this case it likely refers to the way the 2 scheduled entities are given control of the processor so the scheduler decides.