Whose Turn Is It

An engineer writes Peterson's algorithm from memory. Reasoning that turn records whose turn it is to enter, they set it to their own thread id:

int flag[2] = {0, 0};
int turn = 0;

void lock(int self) {
    flag[self] = 1;
    turn = self;                                   // differs from Peterson's
    while (flag[1 - self] == 1 && turn == 1 - self)
        ;                                          // spin
}

void unlock(int self) { flag[self] = 0; }

Assume a sequentially consistent machine (no store reordering). Which interleaving puts both threads in the critical section at the same time?