Thread: Explanation of Code

I am having trouble seeing what this code is doing. I keep getting flag[i] as the only on going into the critical section, which obviously means I am missing something! This isnt homework and I didn't write this code, we are discussing it in class, but I need a better understanding of what is going on! Please explain! Thanks!

So all elements of flag are initially idle, and inital value of turn is between 0 and n-1 (this is what is throwing me off I think.) The processes share:

Code:

enum pstate {idle, want_int, in_cs};
pstate flag[n];
int turn;

Code:

do {
    while(TRUE){
         flag[i] - want_in;
         j = turn;
     
        while( j != i){
                if (flag[j] != idle)
                     j = turn;
                else
                     j = (j + 1) % n;
                }

        flag[i] = in_cs;
        j = 0;

        while ((j<n) && (j == i || flag[j] != in_cs))
               j++;

         if ((j >=n) && (turn == i || flag[turn] == idle))
               break;
}

//critical section

j = (turn + 1) % n;

while (flag[j] == idle)
       j = (j + 1) % n;

turn = j;
flag[i]= idle;

//remainder section

} while (TRUE)