调试 .NET Core 中的死锁

呆呆

发布于 2022-01-09 11:59:44

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发布于 2022-01-09 11:59:44

文章被收录于专栏：centosDai

本文适用于： ✔️ .NET Core 3.1 SDK 及更高版本

本教程将介绍如何调试死锁情况。使用提供的示例 ASP.NET Core Web 应用源代码存储库，可以故意造成死锁。终结点将停止响应并遇到线程累积问题。你将了解如何使用各种工具来分析问题，例如核心转储、核心转储分析和进程跟踪。

在本教程中，你将：

调查已停止响应的应用

生成核心转储文件

分析转储文件中的进程线程

分析调用堆栈和同步块

诊断并解决死锁

先决条件

本教程使用：

.NET Core 3.1 SDK 或更高版本

用于触发场景的示例调试目标 - Web 应用

用于列出进程的 dotnet-trace

收集和分析转储文件的 dotnet-dump

核心转储生成

为了调查应用程序无响应问题，核心转储或内存转储允许你检查其线程的状态以及任何可能存在争用问题的锁定状态。使用以下命令从示例根目录运行示例调试应用程序：

dotnet run

若要查找进程 ID，请使用以下命令：

dotnet-trace ps

注意命令输出中的进程 ID。我们的进程 ID 是 4807，你的进程 ID 将不同。导航到以下 URL，该 URL 是示例站点上的 API 终结点：

https://localhost:5001/api/diagscenario/deadlock

向站点发出的 API 请求将停止响应。让请求运行大约 10-15 秒。然后使用以下命令创建核心转储：

Linux

Windows

sudo dotnet-dump collect -p 4807

dotnet-dump collect -p 4807

分析核心转储

若要启动核心转储分析，请使用以下 dotnet-dump analyze 命令打开核心转储。参数是先前收集的核心转储文件的路径。

dotnet-dump analyze ~/.dotnet/tools/core_20190513_143916

由于要查看可能无响应的应用程序，因此需要对进程中的线程活动有一个总体了解。可以按如下所示使用 threads 命令：

> threads

*0 0x1DBFF (121855)

1 0x1DC01 (121857)

2 0x1DC02 (121858)

3 0x1DC03 (121859)

4 0x1DC04 (121860)

5 0x1DC05 (121861)

6 0x1DC06 (121862)

7 0x1DC07 (121863)

8 0x1DC08 (121864)

9 0x1DC09 (121865)

10 0x1DC0A (121866)

11 0x1DC0D (121869)

12 0x1DC0E (121870)

13 0x1DC10 (121872)

14 0x1DC11 (121873)

15 0x1DC12 (121874)

16 0x1DC13 (121875)

17 0x1DC14 (121876)

18 0x1DC15 (121877)

19 0x1DC1C (121884)

20 0x1DC1D (121885)

21 0x1DC1E (121886)

22 0x1DC21 (121889)

23 0x1DC22 (121890)

24 0x1DC23 (121891)

25 0x1DC24 (121892)

26 0x1DC25 (121893)

...

317 0x1DD48 (122184)

318 0x1DD49 (122185)

319 0x1DD4A (122186)

320 0x1DD4B (122187)

321 0x1DD4C (122188)

该输出显示进程中当前运行的所有线程及其关联的调试器线程 ID 和操作系统线程 ID。基于输出，有超过 300 个线程。

下一步是通过获取每个线程的调用堆栈来更好地了解线程当前正在执行的操作。 clrstack 命令可用于输出调用堆栈。它既可以输出单个调用堆栈，也可以输出所有调用堆栈。使用以下命令输出进程中所有线程的所有调用堆栈：

clrstack -all

输出的典型部分如下所示：

...

Child SP IP Call Site

00007F2AE37B5680 00007f305abc6360 [GCFrame: 00007f2ae37b5680]

00007F2AE37B5770 00007f305abc6360 [GCFrame: 00007f2ae37b5770]

00007F2AE37B57D0 00007f305abc6360 [HelperMethodFrame_1OBJ: 00007f2ae37b57d0] System.Threading.Monitor.ReliableEnter(System.Object, Boolean ByRef)

00007F2AE37B5920 00007F2FE392B31F testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_1() [/home/marioh/webapi/Controllers/diagscenario.cs @ 36]

00007F2AE37B5950 00007F2FE392B46D System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/__w/3/s/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs @ 201]

00007F2AE37B5CA0 00007f30593044af [GCFrame: 00007f2ae37b5ca0]

00007F2AE37B5D70 00007f30593044af [DebuggerU2MCatchHandlerFrame: 00007f2ae37b5d70]

OS Thread Id: 0x1dc82

Child SP IP Call Site

00007F2AE2FB4680 00007f305abc6360 [GCFrame: 00007f2ae2fb4680]

00007F2AE2FB4770 00007f305abc6360 [GCFrame: 00007f2ae2fb4770]

00007F2AE2FB47D0 00007f305abc6360 [HelperMethodFrame_1OBJ: 00007f2ae2fb47d0] System.Threading.Monitor.ReliableEnter(System.Object, Boolean ByRef)

00007F2AE2FB4920 00007F2FE392B31F testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_1() [/home/marioh/webapi/Controllers/diagscenario.cs @ 36]

00007F2AE2FB4950 00007F2FE392B46D System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/__w/3/s/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs @ 201]

00007F2AE2FB4CA0 00007f30593044af [GCFrame: 00007f2ae2fb4ca0]

00007F2AE2FB4D70 00007f30593044af [DebuggerU2MCatchHandlerFrame: 00007f2ae2fb4d70]

OS Thread Id: 0x1dc83

Child SP IP Call Site

00007F2AE27B3680 00007f305abc6360 [GCFrame: 00007f2ae27b3680]

00007F2AE27B3770 00007f305abc6360 [GCFrame: 00007f2ae27b3770]

00007F2AE27B37D0 00007f305abc6360 [HelperMethodFrame_1OBJ: 00007f2ae27b37d0] System.Threading.Monitor.ReliableEnter(System.Object, Boolean ByRef)

00007F2AE27B3920 00007F2FE392B31F testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_1() [/home/marioh/webapi/Controllers/diagscenario.cs @ 36]

00007F2AE27B3950 00007F2FE392B46D System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/__w/3/s/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs @ 201]

00007F2AE27B3CA0 00007f30593044af [GCFrame: 00007f2ae27b3ca0]

00007F2AE27B3D70 00007f30593044af [DebuggerU2MCatchHandlerFrame: 00007f2ae27b3d70]

OS Thread Id: 0x1dc84

Child SP IP Call Site

00007F2AE1FB2680 00007f305abc6360 [GCFrame: 00007f2ae1fb2680]

00007F2AE1FB2770 00007f305abc6360 [GCFrame: 00007f2ae1fb2770]

00007F2AE1FB27D0 00007f305abc6360 [HelperMethodFrame_1OBJ: 00007f2ae1fb27d0] System.Threading.Monitor.ReliableEnter(System.Object, Boolean ByRef)

00007F2AE1FB2920 00007F2FE392B31F testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_1() [/home/marioh/webapi/Controllers/diagscenario.cs @ 36]

00007F2AE1FB2950 00007F2FE392B46D System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/__w/3/s/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs @ 201]

00007F2AE1FB2CA0 00007f30593044af [GCFrame: 00007f2ae1fb2ca0]

00007F2AE1FB2D70 00007f30593044af [DebuggerU2MCatchHandlerFrame: 00007f2ae1fb2d70]

OS Thread Id: 0x1dc85

Child SP IP Call Site

00007F2AE17B1680 00007f305abc6360 [GCFrame: 00007f2ae17b1680]

00007F2AE17B1770 00007f305abc6360 [GCFrame: 00007f2ae17b1770]

00007F2AE17B17D0 00007f305abc6360 [HelperMethodFrame_1OBJ: 00007f2ae17b17d0] System.Threading.Monitor.ReliableEnter(System.Object, Boolean ByRef)

00007F2AE17B1920 00007F2FE392B31F testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_1() [/home/marioh/webapi/Controllers/diagscenario.cs @ 36]

00007F2AE17B1950 00007F2FE392B46D System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/__w/3/s/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs @ 201]

00007F2AE17B1CA0 00007f30593044af [GCFrame: 00007f2ae17b1ca0]

00007F2AE17B1D70 00007f30593044af [DebuggerU2MCatchHandlerFrame: 00007f2ae17b1d70]

OS Thread Id: 0x1dc86

Child SP IP Call Site

00007F2AE0FB0680 00007f305abc6360 [GCFrame: 00007f2ae0fb0680]

00007F2AE0FB0770 00007f305abc6360 [GCFrame: 00007f2ae0fb0770]

00007F2AE0FB07D0 00007f305abc6360 [HelperMethodFrame_1OBJ: 00007f2ae0fb07d0] System.Threading.Monitor.ReliableEnter(System.Object, Boolean ByRef)

00007F2AE0FB0920 00007F2FE392B31F testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_1() [/home/marioh/webapi/Controllers/diagscenario.cs @ 36]

00007F2AE0FB0950 00007F2FE392B46D System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/__w/3/s/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs @ 201]

00007F2AE0FB0CA0 00007f30593044af [GCFrame: 00007f2ae0fb0ca0]

00007F2AE0FB0D70 00007f30593044af [DebuggerU2MCatchHandlerFrame: 00007f2ae0fb0d70]

OS Thread Id: 0x1dc87

Child SP IP Call Site

00007F2AE07AF680 00007f305abc6360 [GCFrame: 00007f2ae07af680]

00007F2AE07AF770 00007f305abc6360 [GCFrame: 00007f2ae07af770]

00007F2AE07AF7D0 00007f305abc6360 [HelperMethodFrame_1OBJ: 00007f2ae07af7d0] System.Threading.Monitor.ReliableEnter(System.Object, Boolean ByRef)

00007F2AE07AF920 00007F2FE392B31F testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_1() [/home/marioh/webapi/Controllers/diagscenario.cs @ 36]

00007F2AE07AF950 00007F2FE392B46D System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/__w/3/s/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs @ 201]

00007F2AE07AFCA0 00007f30593044af [GCFrame: 00007f2ae07afca0]

00007F2AE07AFD70 00007f30593044af [DebuggerU2MCatchHandlerFrame: 00007f2ae07afd70]

OS Thread Id: 0x1dc88

Child SP IP Call Site

00007F2ADFFAE680 00007f305abc6360 [GCFrame: 00007f2adffae680]

00007F2ADFFAE770 00007f305abc6360 [GCFrame: 00007f2adffae770]

00007F2ADFFAE7D0 00007f305abc6360 [HelperMethodFrame_1OBJ: 00007f2adffae7d0] System.Threading.Monitor.ReliableEnter(System.Object, Boolean ByRef)

00007F2ADFFAE920 00007F2FE392B31F testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_1() [/home/marioh/webapi/Controllers/diagscenario.cs @ 36]

00007F2ADFFAE950 00007F2FE392B46D System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/__w/3/s/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs @ 201]

00007F2ADFFAECA0 00007f30593044af [GCFrame: 00007f2adffaeca0]

00007F2ADFFAED70 00007f30593044af [DebuggerU2MCatchHandlerFrame: 00007f2adffaed70]

...

观察所有 300 多个线程的调用堆栈可以发现一个模式，其中大多数线程共享一个公共调用堆栈：

OS Thread Id: 0x1dc88

Child SP IP Call Site

00007F2ADFFAE680 00007f305abc6360 [GCFrame: 00007f2adffae680]

00007F2ADFFAE770 00007f305abc6360 [GCFrame: 00007f2adffae770]

00007F2ADFFAE7D0 00007f305abc6360 [HelperMethodFrame_1OBJ: 00007f2adffae7d0] System.Threading.Monitor.ReliableEnter(System.Object, Boolean ByRef)

00007F2ADFFAE920 00007F2FE392B31F testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_1() [/home/marioh/webapi/Controllers/diagscenario.cs @ 36]

00007F2ADFFAECA0 00007f30593044af [GCFrame: 00007f2adffaeca0]

00007F2ADFFAED70 00007f30593044af [DebuggerU2MCatchHandlerFrame: 00007f2adffaed70]

该调用堆栈似乎显示请求传入了死锁方法，而死锁方法继而又调用了 Monitor.ReliableEnter。此方法表示这些线程正试图进入监视器锁定。它们正在等待该锁定的可用性。它可能已被其他线程锁定。

下一步是找出实际持有监视器锁定的线程。由于监视器通常将锁定信息存储在同步块表中，因此我们可以使用 syncblk 命令来获取更多信息：

> syncblk

Index SyncBlock MonitorHeld Recursion Owning Thread Info SyncBlock Owner

43 00000246E51268B8 603 1 0000024B713F4E30 5634 28 00000249654b14c0 System.Object

44 00000246E5126908 3 1 0000024B713F47E0 51d4 29 00000249654b14d8 System.Object

-----------------------------

Total 344

CCW 1

RCW 2

ComClassFactory 0

Free 0

两个有趣的列是“MonitorHeld”和“Owning Thread Info” 。 “MonitorHeld”列显示线程是否获取了监视器锁定以及正在等待的线程的数量。 “Owning Thread Info”列显示当前拥有监视器锁定的线程。线程信息有三个不同的子列。第二个子列显示操作系统线程 ID。

此时，我们知道两个不同的线程（0x5634 和 0x51d4）持有监视器锁定。下一步是查看这些线程正在执行的操作。我们需要检查它们是否无限期陷入持有锁定。让我们使用 setthread 和 clrstack 命令切换到每个线程并显示调用堆栈。

若要查看第一个线程，请运行 setthread 命令，并找到 0x5634 线程的索引（我们的索引是 28）。死锁函数正在等待获取某个锁定，但它已拥有该锁定。该函数处于正在等待它已经持有的锁定的死锁状态。

> setthread 28

> clrstack

OS Thread Id: 0x5634 (28)

Child SP IP Call Site

0000004E46AFEAA8 00007fff43a5cbc4 [GCFrame: 0000004e46afeaa8]

0000004E46AFEC18 00007fff43a5cbc4 [GCFrame: 0000004e46afec18]

0000004E46AFEC68 00007fff43a5cbc4 [HelperMethodFrame_1OBJ: 0000004e46afec68] System.Threading.Monitor.Enter(System.Object)

0000004E46AFEDC0 00007FFE5EAF9C80 testwebapi.Controllers.DiagScenarioController.DeadlockFunc() [C:\Users\dapine\Downloads\Diagnostic_scenarios_sample_debug_target\Controllers\DiagnosticScenarios.cs @ 58]

0000004E46AFEE30 00007FFE5EAF9B8C testwebapi.Controllers.DiagScenarioController.<deadlock>b__3_0() [C:\Users\dapine\Downloads\Diagnostic_scenarios_sample_debug_target\Controllers\DiagnosticScenarios.cs @ 26]

0000004E46AFEE80 00007FFEBB251A5B System.Threading.ThreadHelper.ThreadStart_Context(System.Object) [/_/src/System.Private.CoreLib/src/System/Threading/Thread.CoreCLR.cs @ 44]

0000004E46AFEEB0 00007FFE5EAEEEEC System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/_/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs @ 201]

0000004E46AFEF20 00007FFEBB234EAB System.Threading.ThreadHelper.ThreadStart() [/_/src/System.Private.CoreLib/src/System/Threading/Thread.CoreCLR.cs @ 93]

0000004E46AFF138 00007ffebdcc6b63 [GCFrame: 0000004e46aff138]

0000004E46AFF3A0 00007ffebdcc6b63 [DebuggerU2MCatchHandlerFrame: 0000004e46aff3a0]

第二个线程类似。它还尝试获取已拥有的锁定。其余 300 多个正在等待的线程很可能也在等待导致死锁的锁定之一。

请参阅

用于列出进程的 dotnet-trace

用于检查托管内存使用情况的 dotnet-counters

用于收集和分析转储文件的 dotnet-dump

dotnet/diagnostics

后续步骤

.NET Core 中提供哪些诊断工具

本文系外文翻译，前往查看

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