看到很多clr！CLRSemaphore ::在调用堆栈中等待

Question

我们看到很多像以下这样的调用堆栈，我可以知道什么是条件\情况会发生吗？

OS Thread Id: 0x48654 (559) 
Current frame: ntdll!NtWaitForSingleObject+0xa 
Child-SP   RetAddr   Caller, Callee 
00000020a76cf480 00007fffd4ea1118 KERNELBASE!WaitForSingleObjectEx+0x94, calling ntdll!NtWaitForSingleObject 
00000020a76cf520 00007fffce50ce66 clr!CLRSemaphore::Wait+0x8a, calling kernel32!WaitForSingleObjectEx 
00000020a76cf5e0 00007fffce50d247 clr!ThreadpoolMgr::UnfairSemaphore::Wait+0x109, calling clr!CLRSemaphore::Wait 
00000020a76cf620 00007fffce50d330 clr!ThreadpoolMgr::WorkerThreadStart+0x1b9, calling clr!ThreadpoolMgr::UnfairSemaphore::Wait 
00000020a76cf6c0 00007fffce5de8b6 clr!Thread::intermediateThreadProc+0x7d 
00000020a76cfb40 00007fffce5de89f clr!Thread::intermediateThreadProc+0x66, calling clr!_chkstk 
00000020a76cfb80 00007fffd60613d2 kernel32!BaseThreadInitThunk+0x22 
00000020a76cfbb0 00007fffd7be5454 ntdll!RtlUserThreadStart+0x34 
OS Thread Id: 0x3bd4c (560) 
Current frame: ntdll!NtWaitForSingleObject+0xa 
Child-SP   RetAddr   Caller, Callee 
00000020a774e910 00007fffd4ea1118 KERNELBASE!WaitForSingleObjectEx+0x94, calling ntdll!NtWaitForSingleObject 
00000020a774e9b0 00007fffce50ce66 clr!CLRSemaphore::Wait+0x8a, calling kernel32!WaitForSingleObjectEx 
00000020a774ea70 00007fffce50d247 clr!ThreadpoolMgr::UnfairSemaphore::Wait+0x109, calling clr!CLRSemaphore::Wait 
00000020a774eab0 00007fffce50d330 clr!ThreadpoolMgr::WorkerThreadStart+0x1b9, calling clr!ThreadpoolMgr::UnfairSemaphore::Wait 
00000020a774eb50 00007fffce5de8b6 clr!Thread::intermediateThreadProc+0x7d 
00000020a774ec30 00007fffd7c00c75 ntdll!RtlpLowFragHeapAllocFromContext+0x355, calling ntdll!memset 

Answer 1

如已经评论提及@Harry Johnston，这些都是无关的线程池的工作线程。

以下示例可用于复制此类堆栈。它会创建12个线程池工作线程，当调试器中断时，它们都处于闲置状态，就像您看到的一样。

的代码是基于微软的Fibunacci threadpool example：

using System.Diagnostics; 
using System.Threading; 

public class Fibonacci 
{ 
    public void ThreadPoolCallback(object threadContext) 
    { 
     FibOfN = Calculate(N); 
     DoneEvent.Set(); 
    } 

    public int Calculate(int n) 
    { 
     if (n <= 1) return n; 
     return Calculate(n - 1) + Calculate(n - 2); 
    } 

    public int N { get; set; } 
    public int FibOfN { get; private set; } 
    public ManualResetEvent DoneEvent { get; set; } 
} 

public class ClrSemaphoreWaitDemo 
{ 
    static void Main() 
    { 
     const int numberOfTasks = 12; 
     var doneEvents = new ManualResetEvent[numberOfTasks]; 
     var fibArray = new Fibonacci[numberOfTasks]; 
     ThreadPool.SetMaxThreads(numberOfTasks, numberOfTasks); 
     ThreadPool.SetMinThreads(numberOfTasks, numberOfTasks); 

     for (int i = 0; i < numberOfTasks; i++) 
     { 
      doneEvents[i] = new ManualResetEvent(false); 
      fibArray[i] = new Fibonacci {N= 4, DoneEvent= doneEvents[i]}; 
      ThreadPool.QueueUserWorkItem(fibArray[i].ThreadPoolCallback, i); 
     } 

     WaitHandle.WaitAll(doneEvents); 
     Debug.WriteLine("Now run .symfix; .reload; .loadby sos clr; !threads; !threads; !findstack clr!CLRSemaphore::Wait"); 
     Debugger.Break(); 
    } 
} 

当中断调试，运行以下命令：

.symfix; .reload; .loadby sos clr; !threads; !threads; !findstack clr!CLRSemaphore::Wait