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我有一个具有最小值和最大值的原子整数变量。两个线程更新变量，一个增加它，另一个减少它。如果递增会使值超过最大值，则线程阻塞并等待条件变量。当值达到最小值时，减量也会发生同样的事情。当值递减并且旧值是最大值时，递减线程应该通知递增线程，并且在递增时应该以相反的方式发生同样的事情。

递减函数体：

if (atomic_var.load(std::memory_order_acquire) == minimum) {
    std::unique_lock<std::mutex> lk(mutex);
    if (atomic_var.load(std::memory_order_acquire) == minimum) {
        //we have hit the minimum so we have to wait for the other thread to increase the variable
        condition_var.wait(lk, [&]() {
            return atomic_var.load(std::memory_order_relaxed) > minimum;
        });
    }

    //do stuff

    std::atomic_fetch_sub_explicit(&atomic_var, 1u, std::memory_order_release);
    lk.unlock();
    condition_var.notify_all();
    return;
}

//do stuff

if (std::atomic_fetch_sub_explicit(&atomic_var, 1u, std::memory_order_release) == maximum) {
    //we have hit the maximum so the other thread might be waiting
    std::atomic_thread_fence(std::memory_order_acquire);
    condition_var.notify_all();
}
//adding condition_var.notify_all() here fixes the problem but I'm afraid
//that causes a bit too great performance penalty when it could be easily avoided

我应该使用哪些内存顺序进行这些检查？我当前的实现似乎导致死锁......

编辑：将所有内存顺序更改为 std::memory_order_seq_cst 似乎并没有解决问题。

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