内部异常的堆栈跟踪

【问题标题】：Stacktrace of an inner exception内部异常的堆栈跟踪
【发布时间】：2018-07-19 17:36:30
【问题描述】：

托管我的 .NET 应用程序的 w3wp 进程随机崩溃。我通过使用 DebugDiag 设置第二次机会异常规则收集了转储文件。以下是我执行的步骤。

lastevent 命令显示 .NET 异常。

0:027> .lastevent
Last event: 1ae4.2e98: CLR exception - code e0434352 (first/second chance not available)

这个线程的堆栈跟踪如下，

0:027> !CLRStack
OS Thread Id: 0x2e98 (68)
        Child SP               IP Call Site
000000266c1bab18 00007fff6e5d95fc [HelperMethodFrame: 000000266c1bab18] 
000000266c1bac00 00007fff5cb38afb System.Runtime.Fx+IOCompletionThunk.UnhandledExceptionFrame(UInt32, UInt32, System.Threading.NativeOverlapped*)
000000266c1bcb48 00007fff6657120d [HelperMethodFrame: 000000266c1bcb48] 
000000266c1bcc30 00007fff5cb359b5 System.Runtime.AsyncResult.Complete(Boolean)
000000266c1bea00 00007fff6657120d [FaultingExceptionFrame: 000000266c1bea00] 
000000266c1bef00 00007fff5bca63a5 System.Web.HttpApplication+AsyncEventExecutionStep.OnAsyncEventCompletion(System.IAsyncResult)
000000266c1bef60 00007fff5cb3586c System.Runtime.AsyncResult.Complete(Boolean)
000000266c1befd0 00007fff570da192 System.ServiceModel.Activation.HostedHttpRequestAsyncResult.OnBeginRequest(System.Object)
000000266c1bf020 00007fff5cb38b63 System.Runtime.IOThreadScheduler+ScheduledOverlapped.IOCallback(UInt32, UInt32, System.Threading.NativeOverlapped*)
000000266c1bf090 00007fff5cb38ac7 System.Runtime.Fx+IOCompletionThunk.UnhandledExceptionFrame(UInt32, UInt32, System.Threading.NativeOverlapped*)
000000266c1bf0f0 00007fff650a045c System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32, UInt32, System.Threading.NativeOverlapped*) [f:\dd\ndp\clr\src\BCL\system\threading\overlapped.cs @ 135]
000000266c1bf2a0 00007fff66416793 [GCFrame: 000000266c1bf2a0] 
000000266c1bf498 00007fff66416793 [DebuggerU2MCatchHandlerFrame: 000000266c1bf498] 
000000266c1bf628 00007fff66416793 [ContextTransitionFrame: 000000266c1bf628] 
000000266c1bf858 00007fff66416793 [DebuggerU2MCatchHandlerFrame: 000000266c1bf858]

pe 命令显示回调异常

0:027> !pe
Exception object: 0000002552364d38
Exception type:   System.Runtime.CallbackException
Message:          Async Callback threw an exception.
InnerException:   System.NullReferenceException, Use !PrintException 0000002552364ae8 to see more.
StackTrace (generated):
    SP               IP               Function
    000000266C1BCC30 00007FFF5CB359B5 System_ServiceModel_Internals_ni!System.Runtime.AsyncResult.Complete(Boolean)+0x235
    000000266C1BEFD0 00007FFF570DA192 System_ServiceModel_Activation_ni!System.ServiceModel.Activation.HostedHttpRequestAsyncResult.OnBeginRequest(System.Object)+0x92
    000000266C1BF020 00007FFF5CB38B63 System_ServiceModel_Internals_ni!System.Runtime.IOThreadScheduler+ScheduledOverlapped.IOCallback(UInt32, UInt32, System.Threading.NativeOverlapped*)+0x53
    000000266C1BF090 00007FFF5CB38AFB System_ServiceModel_Internals_ni!System.Runtime.Fx+IOCompletionThunk.UnhandledExceptionFrame(UInt32, UInt32, System.Threading.NativeOverlapped*)+0x6b
    000000266C1BF0F0 00007FFF650A045C mscorlib_ni!System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32, UInt32, System.Threading.NativeOverlapped*)+0x7c

StackTraceString: <none>
HResult: 80131501
There are nested exceptions on this thread. Run with -nested for details

根据上一个命令的输出，我查找嵌套异常

0:027> !PrintException -nested /d 0000002552364ae8
Exception object: 0000002552364ae8
Exception type:   System.NullReferenceException
Message:          Object reference not set to an instance of an object.
InnerException:   <none>
StackTrace (generated):
    SP               IP               Function
    000000266C1BEF00 00007FFF5BCA63A5 System_Web_ni!System.Web.HttpApplication+AsyncEventExecutionStep.OnAsyncEventCompletion(System.IAsyncResult)+0x55
    000000266C1BEF60 00007FFF5CB3586C System_ServiceModel_Internals_ni!System.Runtime.AsyncResult.Complete(Boolean)+0xec

StackTraceString: <none>
HResult: 80004003

Nested exception -------------------------------------------------------------
Exception object: 0000002552364d38
Exception type:   System.Runtime.CallbackException
Message:          Async Callback threw an exception.
InnerException:   System.NullReferenceException, Use !PrintException 0000002552364ae8 to see more.
StackTrace (generated):
    SP               IP               Function
    000000266C1BCC30 00007FFF5CB359B5 System_ServiceModel_Internals_ni!System.Runtime.AsyncResult.Complete(Boolean)+0x235
    000000266C1BEFD0 00007FFF570DA192 System_ServiceModel_Activation_ni!System.ServiceModel.Activation.HostedHttpRequestAsyncResult.OnBeginRequest(System.Object)+0x92
    000000266C1BF020 00007FFF5CB38B63 System_ServiceModel_Internals_ni!System.Runtime.IOThreadScheduler+ScheduledOverlapped.IOCallback(UInt32, UInt32, System.Threading.NativeOverlapped*)+0x53
    000000266C1BF090 00007FFF5CB38AFB System_ServiceModel_Internals_ni!System.Runtime.Fx+IOCompletionThunk.UnhandledExceptionFrame(UInt32, UInt32, System.Threading.NativeOverlapped*)+0x6b
    000000266C1BF0F0 00007FFF650A045C mscorlib_ni!System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32, UInt32, System.Threading.NativeOverlapped*)+0x7c

StackTraceString: <none>
HResult: 80131501

我的下一步是找到那个 NullReferenceException 的堆栈跟踪

0:027> !do 0000002552364ae8
Name:        System.NullReferenceException
MethodTable: 00007fff652865a0
EEClass:     00007fff64c3f180
Size:        160(0xa0) bytes
File:        C:\Windows\Microsoft.Net\assembly\GAC_64\mscorlib\v4.0_4.0.0.0__b77a5c561934e089\mscorlib.dll
Fields:
              MT    Field   Offset                 Type VT     Attr            Value Name
00007fff65276948  400028e        8        System.String  0 instance 000000244f54d350 _className
00007fff6528f6b8  400028f       10 ...ection.MethodBase  0 instance 0000002552366f58 _exceptionMethod
00007fff65276948  4000290       18        System.String  0 instance 0000000000000000 _exceptionMethodString
00007fff65276948  4000291       20        System.String  0 instance 000000244bf27668 _message
00007fff65286788  4000292       28 ...tions.IDictionary  0 instance 00000025523751a8 _data
00007fff65276b78  4000293       30     System.Exception  0 instance 0000000000000000 _innerException
00007fff65276948  4000294       38        System.String  0 instance 0000000000000000 _helpURL
00007fff65276f28  4000295       40        System.Object  0 instance 0000002552364cc0 _stackTrace
00007fff65276f28  4000296       48        System.Object  0 instance 0000000000000000 _watsonBuckets
00007fff65276948  4000297       50        System.String  0 instance 0000000000000000 _stackTraceString
00007fff65276948  4000298       58        System.String  0 instance 0000000000000000 _remoteStackTraceString
00007fff65279288  4000299       88         System.Int32  1 instance                0 _remoteStackIndex
00007fff65276f28  400029a       60        System.Object  0 instance 0000000000000000 _dynamicMethods
00007fff65279288  400029b       8c         System.Int32  1 instance      -2147467261 _HResult
00007fff65276948  400029c       68        System.String  0 instance 000000255242ce60 _source
00007fff6528fbc0  400029d       78        System.IntPtr  1 instance                0 _xptrs
00007fff65279288  400029e       90         System.Int32  1 instance       -532462766 _xcode
00007fff65250340  400029f       80       System.UIntPtr  1 instance     7fff5bca63a4 _ipForWatsonBuckets
00007fff65265538  40002a0       70 ...ializationManager  0 instance 0000002552364c40 _safeSerializationManager
00007fff65276f28  400028d       b8        System.Object  0   shared           static s_EDILock
                                 >> Domain:Value  000000244acba390:NotInit  000000267072bd80:NotInit  <<

这里我尝试获取 NullReferenceException 的堆栈跟踪。这看起来像一个 SByte 数组。

0:027> !do 0000002552364cc0
Name:        System.SByte[]
MethodTable: 00007fff65202b20
EEClass:     00007fff64c34f60
Size:        120(0x78) bytes
Array:       Rank 1, Number of elements 96, Type SByte (Print Array)
Content:     ........0Qkv&....c.[.......l&...x..[............kX.\....`..l&...`..\............................
Fields:
None

我的期望是获取堆栈跟踪/详细信息，了解导致此空引用的方法/代码行/对象。我也尝试转储 SByte 数组的内容，但这并没有为我提供任何有用的信息。关于如何获取有关此 NullReferenceException 的更多信息的任何建议？

【问题讨论】：

  • 为什么要将 NRE 作为对象转储？您应该先尝试 !sos.pe 0000002552364ae8。另外，请注意 !sos.pe 将为您提供当前线程上的最后一个异常。您可能需要检查 !sos.threads 以查看是否有任何其他线程有相关的（最近的）异常。此外，您可以为所有异常转储托管堆。像 !sos.dumpheap -type Exception 之类的东西。但请注意，旧的异常将被 GC 处理，因此可能不再存在。此外，还有一些预分配的异常（OutOfMemory、StackOverlow、ExecutionEngine、ThreadAbort）可能没有发生，所以要小心。

标签： callback windbg sos sosex


【解决方案1】：

首先，我认为!pe -nested 已经显示了您正在寻找的调用堆栈：

0:027> !PrintException -nested /d 0000002552364ae8
[...]
StackTrace (generated):
    SP               IP               Function
    000000266C1BEF00 00007FFF5BCA63A5 System_Web_ni!System.Web.HttpApplication+AsyncEventExecutionStep.OnAsyncEventCompletion(System.IAsyncResult)+0x55
    000000266C1BEF60 00007FFF5CB3586C System_ServiceModel_Internals_ni!System.Runtime.AsyncResult.Complete(Boolean)+0xec
[...]

接下来，堆栈跟踪正是您在 SByte[] 中看到的内容：它只是一堆数字。

这些数字只有与 PDB 文件一起才有意义。 PDB 文件包含将数字转换为名称的信息。

查看SP 列和IP 列中的值。它们是：

000000266C1BEF00
000000266C1BEF60 
00007FFF5BCA63A5 
00007FFF5CB3586C

现在，使用将这些值转换为文本的转换器：

您会发现可打印字符与 WinDbg 在SByte[] 中显示的输出相匹配：

0:027> !do 0000002552364cc0
[...]
Content:     ........0Qkv&....c.[.......l&...x..[............kX.\....`..l&...`..\............................

由于 little/big-endianness，顺序可能会有所不同。

【讨论】：

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