c# - 为什么我的堆上有两个空的 ThreadAbortExceptions？

Question

我正在使用 WinDBG 调查内存转储，我想知道为什么堆中有两个 System.Threading.ThreadAbortExceptions 都是空的。

对于其他三个已发现的异常，我理解它们存在的原因以及它们是默认创建的:

1. System.ExecutionEngineException

2. System.StackOverflowException

3. System.OutOfMemoryException

WinDBG 输出

0:000> !dumpheap -type System.Threading.ThreadAbortException

Address       MT     Size
010210fc 79330ef8       72     
01021144 79330ef8       72     
total 2 objects

Statistics:
MT    Count    TotalSize Class Name
79330ef8        2          144 System.Threading.ThreadAbortException

Total 2 objects

0:000> !pe 010210fc

Exception object: 010210fc
Exception type: System.Threading.ThreadAbortException
Message: <none>
InnerException: <none>
StackTrace (generated):<none>
StackTraceString: <none>
HResult: 80131530

0:000> !pe 01021144

Exception object: 01021144
Exception type: System.Threading.ThreadAbortException
Message: <none>
InnerException: <none>
StackTrace (generated): <none>
StackTraceString: <none>
HResult: 80131530

所以我的问题是:

1. 这两个是否也是默认创建的？如果是，为什么会有两个？
2. 如果不是，为什么它们是空的？

内存转储来自 Windows 服务。

使用转储中的线程信息进行更新

0:000> !线程

ThreadCount: 14
UnstartedThread: 0
BackgroundThread: 8
PendingThread: 0
DeadThread: 4
Hosted Runtime: no
PreEmptive   GC Alloc           Lock

ID OSID ThreadOBJ    State     GC       Context       Domain   Count APT Exception
0    1 11d4 0015c538      a020 Enabled  00000000:00000000 00163aa0     0 MTA
2    2  71c 0016f6a0      b220 Enabled  00000000:00000000 00163aa0     0 MTA (Finalizer)
3    4 1914 0019ac48   180b220 Enabled  6a205b0c:6a207910 00163aa0     0 MTA (Threadpool Worker)
5    6 1bd4 001b1580   200b020 Enabled  00000000:00000000 00163aa0     0 MTA
6    7 16a4 001bd260   200b220 Enabled  6a1dc7b8:6a1dd910 00163aa0     0 MTA
7    8  870 001c4a58   200b220 Enabled  6a1da740:6a1db910 00163aa0     0 MTA
8    9 2204 001cf798      b220 Enabled  00000000:00000000 00163aa0     0 MTA
9    d  4d8 0021cb98    80a220 Enabled  00000000:00000000 00163aa0     0 MTA (Threadpool Completion Port)
10    e 1b70 002227c0   200b220 Enabled  6a27d820:6a27d910 00163aa0     0 MTA
11   89 2224 68a3fbd0   880b220 Enabled  00000000:00000000 00163aa0     0 MTA (Threadpool Completion Port)
XXXX   11    0 2336e658   8801820 Enabled  00000000:00000000 00163aa0     0 Ukn (Threadpool Completion Port)
XXXX   46    0 16d17270   8801820 Enabled  00000000:00000000 00163aa0     0 Ukn (Threadpool Completion Port)
XXXX   3a    0 16ca7a70   8801820 Enabled  00000000:00000000 00163aa0     0 Ukn (Threadpool Completion Port)
XXXX   3b    0 10e64250   8801820 Enabled  00000000:00000000 00163aa0     0 Ukn (Threadpool Completion Port)

Answer 1

它们由 CLR 预先分配。我将使用 SSCLI20 版本的 CLR 中的这些片段来讲述这个故事:

来自 clr/src/vm/clrex.cpp，CLRException::GetThrowable():

// If creating a normal ThreadAbortException fails, due to OOM or StackOverflow,
// use a pre-created one.
// We do not won't to change a ThreadAbortException into OOM or StackOverflow, because
// it will cause recursive call when escalation policy is on:
// Creating ThreadAbortException fails, we throw OOM.  Escalation leads to ThreadAbort.
// The cycle repeats.
throwable = GetPreallocatedThreadAbortException();

同一个文件，CLRException::GetPreallocatedRudeThreadAbortException() 方法:

// When we are hosted, we pre-create this exception.
// This function should be called only if the exception has been created.
_ASSERTE(g_pPreallocatedRudeThreadAbortException);
return ObjectFromHandle(g_pPreallocatedRudeThreadAbortException);

“循环重复”可以使用一些解释:OutOfMemoryException -> Thread.Abort() -> new ThreadAbortException() -> OutOfMemoryException -> Thread.Abort()。等等。

出于完全相同的原因，同一源文件也有 GetPreallocatedOutOfMemoryException()、GetPreallocatedStackOverflowException() 和 GetPreallocatedExecutionEngineException()。