One ： background

1. Tell a story

I received a friend's help some time ago , Said the number of threads in his program soared , Find out how to solve .

After my analysis , I think this question is very representative , So take it out and share it with you , Or old tools WinDbg.

Two ： WinDbg analysis

1. Are threads really soaring

To check whether the thread has soared , It can be used !t Order to have a look .



0:000:x86> !t

ThreadCount:      382

UnstartedThread:  1

BackgroundThread: 376

PendingThread:    0

DeadThread:       2

Hosted Runtime:   no

                                                                         Lock

       ID OSID ThreadOBJ    State GC Mode     GC Alloc Context  Domain   Count Apt Exception

   0    1  59c 00e52fb0     26020 Preemptive  12D67610:00000000 00e4b408 0     STA

   2    2 2b30 00e61aa0     2b220 Preemptive  00000000:00000000 00e4b408 0     MTA (Finalizer)

   3    3 18cc 00ea72b8   202b220 Preemptive  00000000:00000000 00e4b408 0     MTA

   5    4 1f18 00f02998   1020220 Preemptive  00000000:00000000 00e4b408 0     Ukn (Threadpool Worker)

XXXX    6    0 00f056f8     39820 Preemptive  00000000:00000000 00e4b408 0     MTA

   6    7 2154 09052448   202b020 Preemptive  12E353E0:00000000 00e4b408 0     MTA

   ...

 377  373 2ee8 21a90958   1029220 Preemptive  12D1FCCC:00000000 00e4b408 0     MTA (Threadpool Worker)

 378  374 227c 21b1d510   1029220 Preemptive  12DCBFC8:00000000 00e4b408 0     MTA (Threadpool Worker)

 379  375  7e8 21b1baa8   1029220 Preemptive  12D39ADC:00000000 00e4b408 0     MTA (Threadpool Worker)

 380  376 1d1c 21a8fec8   1029220 Preemptive  12D11F40:00000000 00e4b408 0     MTA (Threadpool Worker)

 381  366 19ec 215c1bd0   1029220 Preemptive  12DB42D8:00000000 00e4b408 0     MTA (Threadpool Worker)

 382  377 1dc8 21b1bff0   1029220 Preemptive  12C71F9C:00000000 00e4b408 0     MTA (Threadpool Worker)

 383  378  f94 215bc750   1029220 Preemptive  12E10568:00000000 00e4b408 0     MTA (Threadpool Worker)

 384  379 17d4 21ac5580   1029220 Preemptive  12D8EE98:00000000 00e4b408 0     MTA (Threadpool Worker)

 385  381 2c1c 21b1b018   1029220 Preemptive  12D0DD00:00000000 00e4b408 0     MTA (Threadpool Worker)

 386  380 309c 21b1da58   1029220 Preemptive  12E25028:00000000 00e4b408 0     MTA (Threadpool Worker)

 387  382 3048 21ac6aa0   1029220 Preemptive  12DFA918:00000000 00e4b408 0     MTA (Threadpool Worker)

From the divination , The main thread is a STA, Description is a form program , A form can do 387 Threads , It's also very awesome , It can also be observed that most of them are ThreadPool Worker , That is, thread pool worker thread .

2. What are these threads doing

Here's a tip , That is, the larger the thread number , They are often newly created , Often you can get some useful things out of this , Just pick up the implication 380 ~ 387 The call stack of these threads .



0:387:x86> ~387s

ntdll_77380000!NtWaitForSingleObject+0xc:

773f29dc c20c00          ret     0Ch

0:387:x86> k

CvRegToMachine(x86) conversion failure for 0x14f

X86MachineInfo::SetVal: unknown register 0 requested

 # ChildEBP RetAddr

00 31fef104 755a1539     ntdll_77380000!NtWaitForSingleObject+0xc

01 31fef104 74b3ee3b     KERNELBASE!WaitForSingleObjectEx+0x99

02 31fef168 74b3efed     clr!CLRSemaphore::Wait+0xbe

03 31fef19c 74b3eee2     clr!ThreadpoolMgr::UnfairSemaphore::Wait+0x13a

04 31fef204 74a54c27     clr!ThreadpoolMgr::WorkerThreadStart+0x328

05 31feff24 7649fa29     clr!Thread::intermediateThreadProc+0x58

06 31feff34 773e7a7e     kernel32!BaseThreadInitThunk+0x19

07 31feff90 773e7a4e     ntdll_77380000!__RtlUserThreadStart+0x2f

0:387:x86> ~386s

ntdll_77380000!NtWaitForSingleObject+0xc:

773f29dc c20c00          ret     0Ch

0:386:x86> k

CvRegToMachine(x86) conversion failure for 0x14f

X86MachineInfo::SetVal: unknown register 0 requested

 # ChildEBP RetAddr

00 31d6ede4 755a1539     ntdll_77380000!NtWaitForSingleObject+0xc

01 31d6ede4 74b3ee3b     KERNELBASE!WaitForSingleObjectEx+0x99

02 31d6ee48 74b3efed     clr!CLRSemaphore::Wait+0xbe

03 31d6ee7c 74b3eee2     clr!ThreadpoolMgr::UnfairSemaphore::Wait+0x13a

04 31d6eee4 74a54c27     clr!ThreadpoolMgr::WorkerThreadStart+0x328

05 31d6fb84 7649fa29     clr!Thread::intermediateThreadProc+0x58

06 31d6fb94 773e7a7e     kernel32!BaseThreadInitThunk+0x19

07 31d6fbf0 773e7a4e     ntdll_77380000!__RtlUserThreadStart+0x2f

0:386:x86> ~385s

ntdll_77380000!NtWaitForSingleObject+0xc:

773f29dc c20c00          ret     0Ch

0:385:x86> k

CvRegToMachine(x86) conversion failure for 0x14f

X86MachineInfo::SetVal: unknown register 0 requested

 # ChildEBP RetAddr

00 31eaee64 755a1539     ntdll_77380000!NtWaitForSingleObject+0xc

01 31eaee64 74b3ee3b     KERNELBASE!WaitForSingleObjectEx+0x99

02 31eaeec8 74b3efed     clr!CLRSemaphore::Wait+0xbe

03 31eaeefc 74b3eee2     clr!ThreadpoolMgr::UnfairSemaphore::Wait+0x13a

04 31eaef64 74a54c27     clr!ThreadpoolMgr::WorkerThreadStart+0x328

05 31eafb7c 7649fa29     clr!Thread::intermediateThreadProc+0x58

06 31eafb8c 773e7a7e     kernel32!BaseThreadInitThunk+0x19

07 31eafbe8 773e7a4e     ntdll_77380000!__RtlUserThreadStart+0x2f

From the thread stack , These threads are UnfairSemaphore Waiting for , This is a normal phenomenon , Because these threads are through UnfairSemaphore Lock to wake up , But strangely enough , Why do these threads occur , Why not die ？

According to experience, predict ： There must be code constantly scheduling Thread pool Threads , Then I did a short-lived operation , As a result, threads in the thread pool are constantly added , There is no threshold at which threads can die .

3. Is the program really scheduling threads frequently

Since the guess is that the program is calling the thread pool thread frequently , What we can do is to observe this moment dump Thread stack of all threads in , See if you can find something valuable , have access to ~*e !clrstack command .

After careful observation, this near 400 A thread stack , Found to have 37 Everywhere System.Threading.Thread.Sleep(Int32), And most of them are HslCommunication.Core.Net.NetworkBase.ThreadPoolCheckTimeOut(System.Object) function , You can clearly see that it is initiated by the thread pool , The next step is to use ILSpy Decompile this function to see what's going on .



        protected void ThreadPoolCheckTimeOut(object obj)

        {

            HslTimeOut hslTimeOut;

            if ((hslTimeOut = obj as HslTimeOut) == null)

            {

                return;

            }

            while (!hslTimeOut.IsSuccessful)

            {

                Thread.Sleep(100);

                if ((DateTime.Now - hslTimeOut.StartTime).TotalMilliseconds > (double)hslTimeOut.DelayTime)

                {

                    if (!hslTimeOut.IsSuccessful)

                    {

                        LogNet?.WriteWarn(ToString(), "Wait Time Out : " + hslTimeOut.DelayTime);

                        hslTimeOut.Operator?.Invoke();

                        hslTimeOut.WorkSocket?.Close();

                    }

                    break;

                }

            }

        }

Next through ILSpy Check the reference of this method , I found many places , Take a few as follows ：



        protected OperateResult<TNetMessage> ReceiveMessage<TNetMessage>(Socket socket, int timeOut, TNetMessage netMsg) where TNetMessage : INetMessage

        {

            ...

            if (timeOut > 0)

            {

                ThreadPool.QueueUserWorkItem(ThreadPoolCheckTimeOut, hslTimeOut);

            }

            ...

        }

        protected OperateResult<Socket> CreateSocketAndConnect(IPEndPoint endPoint, int timeOut)

        {

            ...

            ThreadPool.QueueUserWorkItem(ThreadPoolCheckTimeOut, hslTimeOut);

            ...

        }

        protected void CreateSocketAndConnect(IPEndPoint endPoint, int timeOut, Action<OperateResult<Socket>> connectCallback)

        {

            ...

            ThreadPool.QueueUserWorkItem(ThreadPoolCheckTimeOut, hslTimeOut);

            ...

        }

From the code above , There are indeed some areas for discussion , A great deal of socket Operations are handled by thread pools ThreadPoolCheckTimeOut() function , And in this function, when hslTimeOut.IsSuccessful =false When , stay if ((DateTime.Now - hslTimeOut.StartTime).TotalMilliseconds > (double)hslTimeOut.DelayTime) There will always be sleep, This leads to when socket After the request quantity goes up , Many threads are in sleep state , The thread pool has to generate more threads to process ThreadPoolCheckTimeOut() Logic .

Here we finally found a match Thread pool thread The soaring underlying logic , So let's see HslCommunication.dll What is it , Look for its class library declaration .



[assembly: CompilationRelaxations(8)]

[assembly: RuntimeCompatibility(WrapNonExceptionThrows = true)]

[assembly: Debuggable(DebuggableAttribute.DebuggingModes.IgnoreSymbolStoreSequencePoints)]

[assembly: AssemblyTitle("HslCommunication")]

[assembly: AssemblyDescription(" A framework library , It includes perfect network communication and log components ")]

[assembly: AssemblyConfiguration("")]

[assembly: AssemblyCompany("")]

[assembly: AssemblyProduct("HslCommunication")]

[assembly: AssemblyCopyright("Copyright  By Richard.Hu 2018")]

[assembly: AssemblyTrademark("")]

[assembly: ComVisible(false)]

[assembly: Guid("d3710b78-1b32-4d53-9604-0451a795a2f5")]

[assembly: AssemblyFileVersion("5.3.2.0")]

[assembly: AssemblyVersion("5.3.2.0")]

You can see , This is a commercial component .

3、 ... and ： summary

It is suspected that HslCommunication Problems with components , After a look, I still Business Edition , This is awkward , The suggested solution is as follows ：

1） short-term ：

use ThreadPool.SetMaxThreads Limit the thread limit .

2） long-term ：

Find the author to see if there is the latest version , Or to https://github.com/dathlin/HslCommunication Bring up one issue, Let others solve it systematically .

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