// Indicate the intent to enter the critical section
bIWantToEnter = true;
// Be polite and act as if it is not our
// turn to enter the critical section
iWhoseTurn = HIS_TURN;
// Wait until the other process either does not
// intend to enter the critical section or
// acts as if its our turn to enter
while (bHeWantsToEnter && (iWhoseTurn != MY_TURN)) { }

// Code of critical section comes here
...

bIWantToEnter = false;