Thread leak in JustMock

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Last Updated: 02 Feb 2021 09:32 by ADMIN

Calvin

Created on: 10 Dec 2020 19:18

Type: Bug Report

Thread leak in JustMock

I am a member of the Visual Studio Perf Reliability team

Recently, I’ve found several customer dumps with huge # of threads.

In this dump:

Watson : Cab Search (microsoft.com)

Thd_ThreadStack_telerik_justmock_debugwindow_service_client!Telerik.JustMock.DebugWindow.Service.Client.ConnectionSetupServiceClientBase`[[System.__Canon,mscorlib]].get_ServiceAvailable

2,136,997,888

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There are 2084 threads using 2G mem, most with the stack below:

This is caused by threadpool starvation: the JustMock call ties up a thread for more than 1 second, then another request comes in.

The CLR will create an additional thread after 1 second to satisfy the request. This keeps happening and creates thousands of threads, each with size 1Meg.

00 ntdll!NtWaitForMultipleObjects
01 KERNELBASE!WaitForMultipleObjectsEx
02 clr!WaitForMultipleObjectsEx_SO_TOLERANT
03 clr!Thread::DoAppropriateAptStateWait
04 clr!Thread::DoAppropriateWaitWorker
05 clr!Thread::DoAppropriateWait
06 clr!SOIntolerantTransitionHandler::SetNoException
07 clr!CLREventBase::WaitEx
08 clr!CLREventBase::Wait
09 clr!AwareLock::EnterEpilogHelper
0a clr!ThreadDebugBlockingInfo::PopBlockingItem
0b clr!DebugBlockingItemHolder::{dtor}
0c clr!AwareLock::EnterEpilog
0d clr!AwareLock::Enter
0e clr!AwareLock::Contention
0f clr!JITutil_MonReliableContention
10 Telerik_JustMock_DebugWindow_Service_Client!Telerik.JustMock.DebugWindow.Service.Client.ConnectionSetupServiceClientBase<Telerik.JustMock.DebugWindow.Service.Proxy.TraceEventsSubscriptionServiceProxy>.get_ServiceAvailable
11 Telerik_JustMock_DebugWindow_Service_Client!Telerik.JustMock.DebugWindow.Service.Client.SessionServiceClientBase<Telerik.JustMock.DebugWindow.Service.Proxy.MockRepositorySubscriptionServiceProxy>.KeepAliveTimer_Elapsed
12 System_ni!System.Timers.Timer.MyTimerCallback
13 mscorlib_ni!System.Threading.TimerQueueTimer.CallCallbackInContext
14 mscorlib_ni!System.Threading.ExecutionContext.RunInternal
15 mscorlib_ni!System.Threading.ExecutionContext.Run
16 mscorlib_ni!System.Threading.TimerQueueTimer.CallCallback
17 mscorlib_ni!System.Threading.TimerQueueTimer.Fire
18 mscorlib_ni!System.Threading.TimerQueue.FireNextTimers
19 mscorlib_ni!System.Threading.TimerQueue.AppDomainTimerCallback
1a clr!CallDescrWorkerInternal
1b clr!CallDescrWorkerWithHandler
1c clr!MethodDescCallSite::CallTargetWorker
1d clr!MethodDescCallSite::Call
1e clr!AppDomainTimerCallback_Worker
1f clr!ManagedThreadBase_DispatchInner
20 clr!ManagedThreadBase_DispatchMiddle::__l16::Cleanup::{dtor}
21 clr!ManagedThreadBase_DispatchMiddle
22 clr!ManagedThreadBase_DispatchOuter
23 clr!ManagedThreadBase_FullTransitionWithAD
24 clr!ManagedThreadBase::ThreadPool
25 clr!AppDomainTimerCallback
26 clr!ThreadpoolMgr::AsyncTimerCallbackCompletion
27 clr!UnManagedPerAppDomainTPCount::DispatchWorkItem
28 clr!ThreadpoolMgr::ExecuteWorkRequest
29 clr!ThreadpoolMgr::WorkerThreadStart
2a clr!Thread::intermediateThreadProc
2b kernel32!BaseThreadInitThunk
2c ntdll!__RtlUserThreadStart
2d ntdll!_RtlUserThreadStart

7 comments

ADMIN

Mihail

Posted on: 02 Feb 2021 09:32

Hello Calvin,

The issue was fixed and it is available with our latest release R1 2021 version (2021.1.115.1). You could try it and get back to us if you encounter any issues.

Regards,
Mihail
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ADMIN

Ivo

Posted on: 21 Dec 2020 09:45

Hello Calvin,

Many thanks for your prompt reply. It gives us the confidence that we are on the right way. We will do our best to provide the fix for the upcoming R1.2021 release, which is expected to be available in mid-January next year.

Wish you Happy holidays!

Regards,
Ivo
Progress Telerik

Calvin

Posted on: 18 Dec 2020 20:04

yes, using a timer in a background thread can lead to such problems. It's hard to tell without a debugger and the source code.

One way could be: A timer could be used to kick off a Task on a threadpool thread, and the task might not finish in 1 second, and another Tick causes another to occur.

If the task does something that e.g. does network or disk i/o, it could cause it.

instead of a timer, an alternative is to use

async mytask(cancelationtoken token)

{

await Task.Delay(Timeinterval, token);

}

ADMIN

Ivo

Posted on: 18 Dec 2020 13:31

Hello Calvin,

I have found that we are using Timer-s in the thread context of the background task, which seems to be a potential problem and could be the root cause for the described behavior. Could you please confirm our observations, so we can refactor the code to use a pure async approach?

Regards,
Ivo
Progress Telerik

ADMIN

Ivo

Posted on: 14 Dec 2020 13:26

Hello Calvin,

Thank you for providing this useful sample, it gives an excellent starting point for investigation and helps us to resolve this issue timely.

Regards,
Ivo
Progress Telerik

Calvin

Posted on: 11 Dec 2020 18:29

Sample ThreadPool Thread Leak demo:

ThreadPool/MainWindow.xaml.cs at master · calvinhsia/ThreadPool (github.com)

look at the DoDemoThreadLeakAsync method

ADMIN

Ivo

Posted on: 11 Dec 2020 15:08

Hello Calvin,

Thank you for letting us know about this major issue. Looking at the short description is seems to be related to the DebugWindow feature, which has been added recently to the product and is still in beta. We will start the investigation and will get back to you as soon as we have more info. It will take some time to be completed, so I would like to ask for patience.

Regards,
Ivo
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