Critical Section Problem

Consider a system consisting of n processes (P₀, P₁, ………P_{n -1} ) each process has a segment of code which is known as critical section in which the process may be changing common variable, updating a table, writing a file and so on. The important feature of the system is that when the process is executing in its critical section no other process is to be allowed to execute in its critical section. The execution of critical sections by the processes is a mutually exclusive. The critical section problem is to design a protocol that the process can use to cooperate each process must request permission to enter its critical section. The section of code implementing this request is the entry section. The critical section is followed on exit section. The remaining code is the remainder section.
Example:
While (1)
{
Entry Section;
Critical Section;
Exit Section;
Remainder Section;
}

A solution to the critical section problem must satisfy the following three conditions.
1. Mutual Exclusion: If process P_i is executing in its critical section then no any other process can be executing in their critical section.
2. Progress: If no process is executing in its critical section and some process wish to enter their critical sections then only those process that are not executing in their remainder section can enter its critical section next.
3. Bounded waiting: There exists a bound on the number of times that other processes are allowed to enter their critical sections after a process has made a request.