C++ 11 自旋锁

// Spin lock implementation.
// BasicLockable.
// Async-signal safe.
// unlock() "synchronizes with" lock().
class spinlock {
    std::atomic<bool> _busy = { false };
public:
    spinlock() = default;
    spinlock(const spinlock&) = delete;
    
    ~spinlock() { assert(!_busy.load(std::memory_order_relaxed)); }

    void lock() noexcept {
        while (_busy.exchange(true, std::memory_order_acquire)) {
            _mm_pause();
        }
    }

    void unlock() noexcept {
        _busy.store(false, std::memory_order_release);
    }
};