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copied!<p>To find out which object the thread is waiting for, you will have to do some debugging.</p> <p>First, start with the stack trace that you have:</p> <blockquote> <p>0:000> !CLRStack<br> OS Thread Id: 0x25a8 (0)<br> ESP EIP<br> 001af038 77455e74 [GCFrame: 001af038]<br> 001af108 77455e74 [HelperMethodFrame_1OBJ: 001af108] System.Threading.Monitor.Enter(System.Object)<br> 001af160 00290192 ConsoleApplication1.MyClass.Main(System.String[])<br> 001af3c0 70fc1b4c [GCFrame: 001af3c0] </p> </blockquote> <p>Find out the frame that is calling Monitor.Enter(). In this case it is MyClass::Main(string [] args)</p> <blockquote> <p>001af160 00290192 ConsoleApplication1.MyClass.Main(System.String[]) </p> </blockquote> <p>Now you need to disassemble the caller. Use !sos.u [eip] to do that.</p> <pre><code> 0:000> !u 00d10177 Normal JIT generated code Program.Main(System.String[]) Begin 00d100f8, size 9d 00d100f8 55 push ebp 00d100f9 8bec mov ebp,esp 00d100fb 83ec10 sub esp,10h 00d100fe 894dfc mov dword ptr [ebp-4],ecx 00d10101 833de430970000 cmp dword ptr ds:[9730E4h],0 00d10108 7405 je 00d1010f 00d1010a e802a63b79 call mscorwks!JIT_DbgIsJustMyCode (7a0ca711) 00d1010f 33d2 xor edx,edx 00d10111 8955f8 mov dword ptr [ebp-8],edx 00d10114 90 nop *** WARNING: Unable to verify checksum for C:\WINDOWS\assembly\NativeImages_v2.0.50727_32\mscorlib\7bffd7ff2009f421fe5d229927588496\mscorlib.ni.dll 00d10115 b9fc7e3179 mov ecx,offset mscorlib_ni+0x257efc (79317efc) (MT: System.Threading.ThreadStart) 00d1011a e8ad1fc5ff call 009620cc (JitHelp: CORINFO_HELP_NEWSFAST_CHKRESTORE) 00d1011f 8945f4 mov dword ptr [ebp-0Ch],eax 00d10122 b858c09700 mov eax,97C058h 00d10127 50 push eax 00d10128 6864203b00 push 3B2064h 00d1012d 8b4df4 mov ecx,dword ptr [ebp-0Ch] 00d10130 33d2 xor edx,edx 00d10132 e8b9a45678 call mscorlib_ni+0x1ba5f0 (7927a5f0) (System.MulticastDelegate.CtorOpened(System.Object, IntPtr, IntPtr), mdToken: 060003bf) 00d10137 b9f8103379 mov ecx,offset mscorlib_ni+0x2710f8 (793310f8) (MT: System.Threading.Thread) 00d1013c e8c3c41679 call mscorwks!JIT_NewFast (79e7c604) 00d10141 8945f0 mov dword ptr [ebp-10h],eax 00d10144 8b55f4 mov edx,dword ptr [ebp-0Ch] 00d10147 8b4df0 mov ecx,dword ptr [ebp-10h] 00d1014a e8e1685c78 call mscorlib_ni+0x216a30 (792d6a30) (System.Threading.Thread..ctor(System.Threading.ThreadStart), mdToken: 060012ab) 00d1014f 8b45f0 mov eax,dword ptr [ebp-10h] 00d10152 8945f8 mov dword ptr [ebp-8],eax 00d10155 8b4df8 mov ecx,dword ptr [ebp-8] 00d10158 3909 cmp dword ptr [ecx],ecx 00d1015a e861695c78 call mscorlib_ni+0x216ac0 (792d6ac0) (System.Threading.Thread.Start(), mdToken: 060012b1) 00d1015f 90 nop 00d10160 8b0d30202e02 mov ecx,dword ptr ds:[22E2030h] ("Acquiring lock") 00d10166 e89d38a878 call mscorlib_ni+0x6d3a08 (79793a08) (System.Console.WriteLine(System.String), mdToken: 060007c8) 00d1016b 90 nop 00d1016c 8b0dfc1e2e02 mov ecx,dword ptr ds:[22E1EFCh] (Object: SyncBlock) 00d10172 e8ae281679 call mscorwks!JIT_MonEnterWorker (79e72a25) >>> 00d10177 90 nop 00d10178 8b0d34202e02 mov ecx,dword ptr ds:[22E2034h] ("Releasing lock") 00d1017e e88538a878 call mscorlib_ni+0x6d3a08 (79793a08) (System.Console.WriteLine(System.String), mdToken: 060007c8) 00d10183 90 nop 00d10184 8b0dfc1e2e02 mov ecx,dword ptr ds:[22E1EFCh] (Object: SyncBlock) 00d1018a e8102b1679 call mscorwks!JIT_MonExitWorker (79e72c9f) 00d1018f 90 nop 00d10190 90 nop 00d10191 8be5 mov esp,ebp 00d10193 5d pop ebp 00d10194 c3 ret </code></pre> <p>Note the call site. At this point you have the following debug spew:</p> <pre> 00d1016c 8b0dfc1e2e02 mov ecx,dword ptr ds:[22E1EFCh] (Object: SyncBlock) 00d10172 e8ae281679 call mscorwks!JIT_MonEnterWorker (79e72a25) >>> 00d10177 90 nop 00d10178 8b0d34202e02 mov ecx,dword ptr ds:[22E2034h] ("Releasing lock") 00d1017e e88538a878 call mscorlib_ni+0x6d3a08 (79793a08) (System.Console.WriteLine(System.String), mdToken: 060007c8) 00d10183 90 nop </pre> <p>Just before the call to JitMon::Enter() you see the address of the object being moved into the ECX register. This is the object your thread is waiting on.</p>

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