how to decrement mutithreaded using fetch_sub and ratomic_thread_fence?

We have a member method (bool try()) which is supposed to be thread-safe which decrements the variable m_count if it is greater than 0 and we try to avoid mutexes and instead use fetch_sub and atomic_thread_fence.

struct Test {
  bool try_wait() {
    if (m_count<1)
        return false;
    int count = m_count.fetch_sub(1, std::memory_order_relaxed);
    std::atomic_thread_fence(std::memory_order_acquire);
    return true;
  }
  Test():m_count(1) {}
private:
  std::atomic<int> m_count;
}

We want to ensure that m_count never becomes less than 0 and that try returns true if m_count is decremented. Above two threads can decrement m_count from 1 to -1 and that is not acceptable.