获取等待un mutex的线程数

Question

从假设无法原子地增加计数器和锁定互斥锁（或获取它的ty）开始，是否有任何多线程库允许读取互斥锁上的等待线程数？

Answer 1

我不知道您编写的是哪种编程语言，但在C＃中，您可以try to get an exclusive lock在一个没有阻塞的对象上，因此您的Mutex实现将如下所示：

class MyMutex
{
    public int LockedThreadsCount
    {
        get { lock (countLock) { return waitingThreads; } }
    }

    public void WaitOne()
    {
        if (!Monitor.TryEnter(mainLock))
        {
            lock (countLock) { waitingThreads++; }
            Monitor.Enter(mainLock);
            lock (countLock) { waitingThreads--; }
        }
    }

    public void Release()
    {
        Monitor.Exit(mainLock);
    }

    private int waitingThreads = 0;
    private object countLock = new object();
    private object mainLock = new object();
}