.Net 内存转储中的大量死线程答案

【问题标题】：Large number of dead threads in .Net memory dump.Net 内存转储中的大量死线程
【发布时间】：2019-11-21 05:45:03
【问题描述】：

在分析 .Net4.5 WCF w3wp 进程的内存转储期间，我遇到了许多被识别为已死线程的线程。 !threads 显示 107 个线程中有 68 个已死，这似乎相当高。我想知道这些线程是否可以容纳大量内存，因为进程最终会高达 20GB+ 并且似乎永远不会下降。

如何检查这些线程并查看这些线程所持有的对象/内存？有这么多正常吗？

0:000> !threads
ThreadCount:      107
UnstartedThread:  0
BackgroundThread: 35
PendingThread:    0
DeadThread:       68
Hosted Runtime:   no

       ID OSID ThreadOBJ           State GC Mode     GC Alloc Context                  Domain           Count Apt Exception
   7    1 16fc 0000009d253a36e0    28220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
  14    2  a64 000000a1702d7560    2b220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Finalizer) 
XXXX    3    0 000000a1702f9390  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Completion Port) 
XXXX    4    0 000000a1702fa270  8038820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
  16    6 21c8 000000a17031f310  102a220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
  17    7 2af4 000000a170327ef0    21220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
  19    9 1b50 000000a1703cccd0  1020220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
  21   10  85c 000000a170416570  202b020 Preemptive  000000A0945502B8:000000A094550FD0 000000a1703360c0 0     MTA 
  25   11 13cc 000000a1711823f0  202b020 Preemptive  000000A094554D60:000000A094554FD0 000000a1703360c0 0     MTA 
  26   12 2044 000000a1711921d0  3029220 Preemptive  0000000000000000:0000000000000000 000000a1703360c0 0     MTA (Threadpool Worker) 
XXXX   16    0 000000a17128a690  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Completion Port) 
XXXX   17    0 000000a1712bd610  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Completion Port) 
XXXX   18    0 000000a1712c5e30  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Completion Port) 
XXXX   19    0 000000a1712c4e90  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Completion Port) 
   2   20  8a4 000000a1712c6600    20220 Preemptive  0000009E8B81C238:0000009E8B81DFD0 0000009d25385d70 0     Ukn 
  18   21 28f8 000000a1712c3720    20220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
  22   22  bfc 000000a1712c3ef0    20220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
  20   23 257c 000000a1712c5660    20220 Preemptive  000000A09457AC30:000000A09457AFD0 0000009d25385d70 0     Ukn 
  23   24 13e0 000000a1712c6dd0    20220 Preemptive  0000009F87F0B5C8:0000009F87F0CFD0 0000009d25385d70 0     Ukn 
XXXX   26    0 000000a1713d8fb0  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
  28   27 2aac 000000a1713dbe90  a029220 Preemptive  0000000000000000:0000000000000000 000000a1703360c0 0     MTA (Threadpool Completion Port) 
XXXX   29    0 000000a1713dc660  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Completion Port) 
  29   30 284c 000000a1713d9f50  202b220 Preemptive  0000000000000000:0000000000000000 000000a1703360c0 0     MTA 
XXXX   31    0 000000a1713da720  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   32    0 000000a1713db6c0  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Completion Port) 
XXXX   33    0 000000a174347600  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   34    0 000000a174344720  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   35    0 000000a174345e90  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   36    0 000000a174346660    39820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
XXXX   37    0 000000a174346e30  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   38    0 000000a1743456c0  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   39    0 000000a1741b9d10  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   40    0 000000a1741bc420  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   41    0 000000a1741bcbf0  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   42    0 000000a1741ba4e0  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   43    0 000000a1741be360  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
   3   44 1e94 000000a1741bd3c0    20220 Preemptive  0000009F87E511F8:0000009F87E52FD0 0000009d25385d70 0     Ukn 
XXXX   45    0 000000a1741bdb90  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
  35   46 12dc 000000a1741bacb0    20220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA 
XXXX   47    0 000000a1741beb30    30820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
XXXX   48    0 000000a1741bf300  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX   49    0 000000a171171f40  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
  36   50 2bb4 000000a171173e80  202b020 Preemptive  0000000000000000:0000000000000000 000000a1703360c0 0     MTA 
  37   51  9e4 000000a171177530  202b020 Preemptive  000000A0945528D0:000000A094552FD0 000000a1703360c0 0     MTA 
  39   53  6d0 000000a171174e20    21220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
  40   54  f34 000000a171172ee0    21220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
  41   55  f74 000000a1711755f0    21220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
  42   56 2198 000000a171174650    21220 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn 
XXXX   57    0 000000a171175dc0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   60    0 000000a171176590  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   62    0 000000a171177d00  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   64    0 000000a171178ca0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   65    0 000000a1741bfad0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   70    0 000000a174344ef0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   71    0 000000a1713d9780  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   69    0 000000a171171770  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   68    0 000000a1711736b0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   67    0 000000a171172710  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   66    0 000000a171176d60  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   59    0 000000a1711784d0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   58    0 000000a1741bbc50  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   63    0 000000a1741c1240  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   61    0 000000a1741c02a0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   28    0 000000a1741c0a70  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   25    0 000000a1712c46c0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   15    0 000000a1713daef0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   14    0 000000a174347dd0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   13    0 000000a16744b400  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   52    0 000000a167448520  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX    8    0 000000a16744bbd0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   72    0 000000a16744ac30  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Completion Port) 
XXXX   73    0 000000a16744a460  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   74    0 000000a171268f50  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   75    0 000000a1712658a0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   76    0 000000a171269720  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   77    0 000000a171266070  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   78    0 000000a1712677e0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   79    0 000000a171269ef0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   80    0 000000a171266840  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   81    0 000000a17126a6c0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   82    0 000000a171267010  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   83    0 000000a17126ae90  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
XXXX    5    0 000000a171268780  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Completion Port) 
  43   84  dcc 000000a17126b660  8029220 Preemptive  0000009D9D1B3B88:0000009D9D1B3FD0 0000009d25385d70 0     MTA (Threadpool Completion Port) 
XXXX   85    0 000000a171267fb0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   86    0 000000a17126be30  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
  46   87 1e54 000000a17126c600  1029220 Preemptive  000000A094575068:000000A094576FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   88    0 000000a17126cdd0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
  45   89 1db8 000000a16744c3a0  1029220 Preemptive  000000A094577250:000000A094578FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   90    0 000000a167448cf0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
XXXX   91    0 000000a16744cb70  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   92    0 000000a1674494c0  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   93    0 000000a16744d340  1039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Worker) 
  50   94 15a4 000000a16744db10  1029220 Preemptive  000000A09456AF80:000000A09456AFD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  47   95 29c8 000000a167449c90  1029220 Preemptive  000000A094573D08:000000A094574FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  48   96 28c4 000000a16744e2e0  1029220 Preemptive  000000A094548ED8:000000A094548FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  49   97  69c 000000a16744eab0  1029220 Preemptive  0000009D9D1863F0:0000009D9D187FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
XXXX   98    0 000000a16744fa50  8039820 Preemptive  0000000000000000:0000000000000000 0000009d25385d70 0     Ukn (Threadpool Completion Port) 
  51   99 2bac 000000a16744f280  8029220 Preemptive  0000009F87F32660:0000009F87F32FD0 0000009d25385d70 0     MTA (Threadpool Completion Port) 
  52  101  c40 000000a174599040  1029220 Preemptive  0000009D9D178538:0000009D9D179FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  54  102 1e5c 000000a174598870  1029220 Preemptive  0000009F87F51578:0000009F87F52FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  56  103 2b68 000000a174596930  1029220 Preemptive  0000009D9D188E70:0000009D9D189FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  55  104 2924 000000a174595990  1029220 Preemptive  0000009D9D18C290:0000009D9D18DFD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  53  105  2f0 000000a174599810  1029220 Preemptive  0000009E8B89EFD0:0000009E8B89FFD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  57  106  f5c 000000a174596160  1029220 Preemptive  0000009E8B894828:0000009E8B895FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  58  107  20c 000000a174599fe0  1029220 Preemptive  0000009F87F53258:0000009F87F54FD0 0000009d25385d70 0     MTA (Threadpool Worker) 
  60  100 1f60 000000a17459a7b0  8029220 Preemptive  0000009F87F7B1A8:0000009F87F7CFD0 0000009d25385d70 0     MTA (Threadpool Completion Port)

【问题讨论】：

您不能假设 anything 在您决定进行小型转储时是正常的。死线程不能拥有任何内存分配，线程对象没有得到清理，因为内存管理出现问题是一个明智的结论。也许你不应该等太久再做 minidump。
每个托管线程都由本机线程和 System.Thread 对象支持。在您的情况下，“死线程”确实表明本机线程不再存在，但曾经配对的 System.Thread 对象仍然存在。在该线程上创建的可能对象仍在被引用，因此无法被 GC。您可以转储 System.Thread 对象的根以跟踪引用。您还应该检查终结队列，看看它是否过大或被阻塞。
@Dono，我如何使用 ThreadObj 获取 Thread 对象，因为由于 XXX，我没有线程号。
@Pascal 你不能。只需从托管堆中转储所有 System.Threading.Thread 对象。您必须过滤结果。

标签： 64-bit .net-4.5 windbg

【解决方案1】：

我想知道这些线程是否可以容纳大量内存

记住以下规则：一个进程提供内存，一个线程消耗CPU时间。反之亦然：进程不运行，线程不持有内存。如果有人说“我的进程仍在运行”，那是对“我的进程至少有一个仍在运行的线程”这句话的简化。

死线程（标记为XXXX）意味着内存中有一个.NET Thread 对象，而“真正的”线程（操作系统维护的内核对象）已经消失。

以下是针对这种情况的 MCVE：

using System;
using System.Collections.Generic;
using System.Threading;

namespace DeadThreadExample
{
    class Program
    {
        static List<Thread> AllThreadsIEverStarted = new List<Thread>();
        static void Main()
        {
            for(int i=0; i<1000; i++)
            {
                Thread t = new Thread(DoNothing);
                t.Start();
                AllThreadsIEverStarted.Add(t);
                t.Join();
            }
            Console.WriteLine("There should be 1000 dead threads now. Debug it with WinDbg and SOS !threads");
            Console.ReadLine();
        }

        private static void DoNothing()
        {
            // Just nothing
        }
    }
}

调试会话是：

0:006> !threads
PDB symbol for clr.dll not loaded
ThreadCount:      1002
UnstartedThread:  0
BackgroundThread: 1
PendingThread:    0
DeadThread:       1000
Hosted Runtime:   no
[...]

可以容纳大量内存

0:006> !dumpheap -stat
Statistics:
      MT    Count    TotalSize Class Name
[...]
53dde9b0     1000        20000 System.Threading.ThreadHelper
53d66bf0     1000        44000 System.Threading.ExecutionContext
53d62e10     1001        52052 System.Threading.Thread
53dad5cc     2000        64000 System.Threading.ThreadStart

所以，是的，如果您将静态集合称为泄漏，则存在“内存泄漏”。也许这不是泄漏，因为您在某个时间点需要该信息。一旦收集被清除，它就不再是泄漏。

1000 个死线程相当于 ~180 kB “内存泄漏”。我不会称之为“大量”。即使您将对象作为参数传递（使用ParameterizedThreadStart），似乎Thread 对象的属性m_ThreadStartArg 也没有设置，所以我几乎看不出会有更多的内存泄漏。

如果您不喜欢这种情况，请使用内存分析器并找出哪些 GC 根仍然具有对这些线程的引用。

有这么多正常吗？

也许你只是不走运。它们可能会随着下一次垃圾回收而消失。

我如何检查这些线程并查看它们持有的对象/内存？

使用!dumpheap -stat -type，然后使用dumpheap -mt，然后使用!do：

0:006> !dumpheap -stat -type Thread
Statistics:
      MT    Count    TotalSize Class Name
[...]
53d62e10     1001        52052 System.Threading.Thread

0:006> !dumpheap -mt 53d62e10  
 Address       MT     Size
02ec247c 53d62e10       52     
02ec2504 53d62e10       52     
[...]  

Statistics:
      MT    Count    TotalSize Class Name
53d62e10     1001        52052 System.Threading.Thread
Total 1001 objects

0:006> !do 02ec247c
Name:        System.Threading.Thread
MethodTable: 53d62e10
EEClass:     53e679a4
Size:        52(0x34) bytes
File:        C:\WINDOWS\Microsoft.Net\assembly\GAC_32\mscorlib\v4.0_4.0.0.0__b77a5c561934e089\mscorlib.dll
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
53d6cd68  400192d        4 ....Contexts.Context  0 instance 00000000 m_Context
53d66bf0  400192e        8 ....ExecutionContext  0 instance 00000000 m_ExecutionContext
53d624e4  400192f        c        System.String  0 instance 00000000 m_Name
53d63c70  4001930       10      System.Delegate  0 instance 00000000 m_Delegate
53d65074  4001931       14 ...ation.CultureInfo  0 instance 00000000 m_CurrentCulture
53d65074  4001932       18 ...ation.CultureInfo  0 instance 00000000 m_CurrentUICulture
53d62734  4001933       1c        System.Object  0 instance 00000000 m_ThreadStartArg
53d67b18  4001934       20        System.IntPtr  1 instance  11519f8 DONT_USE_InternalThread
53d642a8  4001935       24         System.Int32  1 instance        2 m_Priority
53d642a8  4001936       28         System.Int32  1 instance        3 m_ManagedThreadId
53d6878c  4001937       2c       System.Boolean  1 instance        0 m_ExecutionContextBelongsToOuterScope
[ ... static ... ]

【讨论】：

Thomas，也许我没有正确地提出我的问题。当我谈论线程占用的空间量时，我不仅仅谈论 Thread 对象本身，还谈论它可能保留的对其他对象的每个引用，并防止垃圾收集器清理它们。如果我有一个死线程对象持有一个大型 DataTable 对象（想想 100K++ 行），那么内存将永远不会被回收。
在线程上执行转储堆时，我不知道哪个死了。在执行 !threads 时，我确实看到了哪一个已经死了，但是我如何使用 ThreadObj 来查询它？
@Pascal：我目前看到的持有额外内存的Thread 对象的唯一方法是成员m_ThreadStartArg。在我的测试中，我无法看到该属性集。恕我直言，数据表更有可能以其他方式泄露。使用 .NET 内存分析器，如 JetBrains dotTrace。它会告诉您对象连接到的位置。
@Pascal：我想唯一的方法是通过DONT_USE_InternalThread 属性。但我不知道谁来解释 IntPtr 以返回操作系统线程。
@eranotzap：那是 WinDbg (UI) 或 CDB（命令行）。这两个调试器中的命令是等效的。它需要 SOS 扩展。