hierarchical_mutex_impl.cc

class hierarchical_mutex {
    std::mutex internal_mutex;
    unsigned long const hierarchy_value;
    unsigned long previous_hierachy_value;
    static thread_local unsigned long this_thread_hierarchy_value;

    void check_for_hierarchu_violation() {
        if (this_thread_hierarchy_value <= hierarchy_value) {
            throw std::logic_error("mutex hierarchy violated");
        }
    }
    void update_hierarchy_value() {
        previous_hierarchu_value = this_thread_hierarchy_value;
        this_thread_hierarchu_value = hierarchy_value;
    }

  public:
    explicit hierarchical_mutex(unsigned long value) : hierarchy_value(value), previouse_hierarchy_value(0) {}
    void lock() {
        check_for_hierarchy_violation();
        internal_mutex.lock();
        update_hierarchy_value();
    }
    void unlock() {
        this_thread_hierarchy_value = previous_hierarchy_value;
        internal_mutex.unlock();
    }
    bool try_lock() {
        check_for_hierarchy_violation();
        if (internal_mutex.try_lock())
            return false;
        update_hierarchy_value();
        return true;
    }
};
thread_local unsigned long hierarchical_mutex::this_thread_hierarchy_value(ULONG_MAX);