ManualResetEventSlim:调用.Set()后紧跟.Reset()不会'；t释放*any*个等待线程

ManualResetEventSlim:调用.Set((后紧跟.Reset((不会释放任何等待线程

(注意：ManualResetEvent也会发生这种情况，而不仅仅是ManualResetEventSlim。(

我在发布和调试模式下都尝试了下面的代码。我将它作为一个32位版本运行，在四核处理器上运行的Windows7 64位上使用.Net 4。我从Visual Studio 2012编译了它(因此安装了.Net 4.5(。

当我在我的系统上运行它时，输出是：

Waiting for 20 threads to start
Thread 1 started.
Thread 2 started.
Thread 3 started.
Thread 4 started.
Thread 0 started.
Thread 7 started.
Thread 6 started.
Thread 5 started.
Thread 8 started.
Thread 9 started.
Thread 10 started.
Thread 11 started.
Thread 12 started.
Thread 13 started.
Thread 14 started.
Thread 15 started.
Thread 16 started.
Thread 17 started.
Thread 18 started.
Thread 19 started.
Threads all started. Setting signal now.
0/20 threads received the signal.

因此，设置然后立即重置事件并没有释放任何线程。如果取消对Thread.Sleep((的注释，那么它们都将被释放。

这似乎有些出乎意料。

有人能解释吗？

using System;
using System.Threading;
using System.Threading.Tasks;
namespace Demo
{
    public static class Program
    {
        private static void Main(string[] args)
        {
            _startCounter = new CountdownEvent(NUM_THREADS); // Used to count #started threads.
            for (int i = 0; i < NUM_THREADS; ++i)
            {
                int id = i;
                Task.Factory.StartNew(() => test(id));
            }
            Console.WriteLine("Waiting for " + NUM_THREADS + " threads to start");
            _startCounter.Wait(); // Wait for all the threads to have called _startCounter.Signal() 
            Thread.Sleep(100); // Just a little extra delay. Not really needed.
            Console.WriteLine("Threads all started. Setting signal now.");
            _signal.Set();
            // Thread.Sleep(50); // With no sleep at all, NO threads receive the signal.
            _signal.Reset();
            Thread.Sleep(1000);
            Console.WriteLine("'n{0}/{1} threads received the signal.'n'n", _signalledCount, NUM_THREADS);
            Console.WriteLine("Press any key to exit.");
            Console.ReadKey();
        }
        private static void test(int id)
        {
            Console.WriteLine("Thread " + id + " started.");
            _startCounter.Signal();
            _signal.Wait();
            Interlocked.Increment(ref _signalledCount);
            Console.WriteLine("Task " + id + " received the signal.");
        }
        private const int NUM_THREADS = 20;
        private static readonly ManualResetEventSlim _signal = new ManualResetEventSlim();
        private static CountdownEvent _startCounter;
        private static int _signalledCount;
    }
}

注意：这个问题也提出了类似的问题，但似乎没有答案(除了确认是的，这是可能发生的(。

ManualResetEvent未一致释放所有等待线程的问题

[编辑]

正如Ian Griffiths在下面指出的那样，答案是所使用的底层Windows API并不是为了支持这一点而设计的。

遗憾的是，ManualResetEventSlim.Set((的Microsoft文档错误地指出它是

将事件的状态设置为已发出信号，这允许一个或多个等待事件继续的线程。

显然，"一个或多个"应该是"零个或更多"。