#include <atomic>

class atomic_spin_lock {
  std::atomic_flag locked = ATOMIC_FLAG_INIT ;
public:
  void lock() noexcept {
    while (locked.test_and_set(std::memory_order_acquire)) { ; /* TODO cpu_relax() here for better performance */ }
  }

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