The first known correct software solution to the critical-section problem for n processes with a lower bound on waiting of n ? 1 turns was presented by Eisenberg and McGuire.
The processes share the following variables: enum pstate {idle, want in, in cs}; pstate flag[n];
int turn;
All the elements of flag are initially idle; the initial value of turn is immaterial (between 0 and n-1). The structure of process Pi is shown in Figure 6.26.
Prove that the algorithm satisfies all three requirements for the critical-section problem.