一、互斥锁的实现1

class mutex
{
public:
    void lock()
    {
        while (locked);     // 关键行1
        locked = 1;         // 关键行2
    }

    void unlock() 
    {
        locked = 0;
    }

private:
    int locked = 0;
};

二、自旋锁的实现

class lock_t
{
private:
    int flag;

public:
    lock_t()
    {
        flag = 0;
    }

    void lock()
    {
        while (TestAndSet(flag, 1) == 1); 
        // 不停地自旋，TestAndSet就是将1和flag的值原子的交换，硬件指令
    }

    void unlock() { flag = 0; }
};