std::atomic_flag实现自旋锁和互斥锁

锁

class Mutex
{
    DISABLE_COPY(Mutex)
public:
    Mutex() {}
    ~Mutex() {}

    void lock()
    {
        while (m_atomic_flag.test_and_set(std::memory_order_acquire)) {
            // 有这一行 ？ 互斥锁：自旋锁；
            // std::this_thread::yield();
        }
    }

    void unlock() { m_atomic_flag.clear(std::memory_order_release); }

private:
    std::atomic_flag m_atomic_flag;
};

RAII锁定

class MutexLocker
{
    Mutex *m_mutex;

    DISABLE_COPY(MutexLocker)
public:
    MutexLocker(Mutex *mutex)
        : m_mutex(mutex)
    {
        m_mutex->lock();
    }

    ~MutexLocker() { m_mutex->unlock(); }
};

测试

class TestMutex
{
    Mutex m_mutex;
    int count = 0;

public:
    void run()
    {
        while (count < 30) {
            MutexLocker locker(&m_mutex);
            std::cout << std::this_thread::get_id() << ": " << ++count << std::endl;
        }
    }
};

int main(int argc, char *argv[])
{
    TestMutex test;
    std::thread t1(std::bind(&TestMutex::run, &test));
    std::thread t2(std::bind(&TestMutex::run, &test));
    t1.join();
    t2.join();

    return 0;
}

结果

自旋

互斥