Peterson算法中为何不将turn变量设置为当前进程？

在Peterson算法中，进程会将turn变量设置为另一个进程。但我想知道为何我们不将turn变量设置为当前进程，示例代码如下：

void process0() {
    flag[0] = 1; // Process 0 wants to access the critical section
    turn = 0; // It's Process 0's turn to access the critical section
    while (flag[1] && turn == 1); // If Process 1 wants to access the critical section and it IS Process 1's turn, then Process 0 should wait
    // Process 0 accesses the critical section
    flag[0] = 0; // Process 0 quits the critical section
    // Remaining codes
}

void process1() {
    flag[1] = 1; // Process 1 wants to access the critical section
    turn = 1; // It's Process 1's turn to access the critical section
    while (flag[0] && turn == 0); // If Process 0 wants to access the critical section and it IS Process 0's turn, then Process 1 should wait
    // Process 1 accesses the critical section
    flag[1] = 0; // Process 1 quits the critical section
    // Remaining codes
}

看起来始终有且仅有一个进程能进入临界区，那为何不将turn变量设为当前进程编号？

我用以下Python代码进行了测试：

import threading, random


END_POSSIBILITY = 0.001 # The possibility that one process finishes running

flag = [False, False]
turn = 0

class CriticalSection:
    def __init__(self) -> None:
        self.visitor = -1

    def visit(self, visitor: int) -> None:
        if self.visitor == -1:
            self.visitor = visitor
        else:
            raise Exception(f"CRITICAL SECTION IS ALREADY BEING VISITED BY PROCESS {self.visitor}, CANNOT BE VISITED BY {visitor}!!!")
        
    def unvisit(self) -> None:
        self.visitor = -1


critical_section = CriticalSection()

def process0():
    global turn
    
    while True:
        flag[0] = True

        turn = 0

        while flag[1] and turn == 1:
            pass

        critical_section.visit(0)

        flag[0] = False
        critical_section.unvisit()

        if (random.random() <= END_POSSIBILITY):
            break


def process1():
    global turn
    
    while True:
        flag[1] = True

        turn = 1

        while flag[0] and turn == 0:
            pass

        critical_section.visit(1)

        flag[1] = False
        critical_section.unvisit()

        if (random.random() <= END_POSSIBILITY):
            break


thread0 = threading.Thread(target=process0)
thread1 = threading.Thread(target=process1)

thread0.start()
thread1.start()

多次运行该代码后，一切均正常。

内容的提问来源于stack exchange，提问作者yvvt0379