Rewrite of example from http://preshing.com/20170612/can-reordering-of-release-acquire-operations-introduce-deadlock/

spinlock-example.cpp

#include <atomic>

class SpinLock {
    std::atomic<int> m_flag = 0;
    
public:
    void lock() {
        int expected = 0;
        while (!m_flag.compare_exchange_weak(expected, 1, std::memory_order_acquire)) {
            expected = 0;
        }
    }
    
    void unlock() {
        m_flag.store(0, std::memory_order_release);
    }
};

SpinLock A;
SpinLock B;

void thread1() {
    A.lock();
    A.unlock();
    B.lock();
    B.unlock();
}

void thread2() {
    B.lock();
    A.lock();
    A.unlock();
    B.unlock();    
}