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I have a multi-threaded .NET application that hangs on an OnUserPreferenceChanged event. This is typically caused by a UI control or message loop started on a background thread (see e.g. http://www.ikriv.com/en/prog/info/dotnet/MysteriousHang.html), but as far as I can tell that isn't the case here. I verified this by setting a breakpoint in the WindowsFormsSynchronizationContext (as suggested here http://www.aaronlerch.com/blog/2008/12/15/debugging-ui/) and it is only constructed once, in the main UI thread.

Here's the output from !clrstack in windbg:

0013eea8 7c90e514 [HelperMethodFrame_1OBJ: 0013eea8] System.Threading.WaitHandle.WaitOneNative(Microsoft.Win32.SafeHandles.SafeWaitHandle, UInt32, Boolean, Boolean) 0013ef54 792b68af System.Threading.WaitHandle.WaitOne(Int64, Boolean) 0013ef70 792b6865 System.Threading.WaitHandle.WaitOne(Int32, Boolean) 0013ef84 7b6f1a4f System.Windows.Forms.Control.WaitForWaitHandle(System.Threading.WaitHandle) 0013ef98 7ba2d68b System.Windows.Forms.Control.MarshaledInvoke(System.Windows.Forms.Control, System.Delegate, System.Object[], Boolean) 0013f038 7b6f33ac System.Windows.Forms.Control.Invoke(System.Delegate, System.Object[]) 0013f06c 7b920bd7 System.Windows.Forms.WindowsFormsSynchronizationContext.Send(System.Threading.SendOrPostCallback, System.Object) 0013f084 7a92ed62 Microsoft.Win32.SystemEvents+SystemEventInvokeInfo.Invoke(Boolean, System.Object[]) 0013f0b8 7a92dc8f Microsoft.Win32.SystemEvents.RaiseEvent(Boolean, System.Object, System.Object[]) 0013f104 7a92e227 Microsoft.Win32.SystemEvents.OnUserPreferenceChanged(Int32, IntPtr, IntPtr) 0013f124 7aaa06ec Microsoft.Win32.SystemEvents.WindowProc(IntPtr, Int32, IntPtr, IntPtr)

The last method I can get param info on is:

0013f084 7a92ed62 Microsoft.Win32.SystemEvents+SystemEventInvokeInfo.Invoke(Boolean, System.Object[]) PARAMETERS: this = 0x01404420 checkFinalization = 0x00000001 args = 0x0144a298

Here's my question: How can I get more information here? Ultimately, I'd like to know which objects and/or threads this Invoke is for. Something like "!do 0x01404420" or "!do 0x0144a298" but I don't know where to go from there.

JMH
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2 Answers2

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Search for exceptions in the heap by using !dumpheap -type Exception.

Also you can see the value of variables in a class,which will be useful to understand the state of the class. Use !dumpheap -type ClassName. You will get a MT(Method Table) address. From MT address see the Object address. Use !do address to dump the class.

Use !syncblk to see the locked threads

Rockstart
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  • That's good info but in this case I have a known deadlock scenario: Thread 0 is waiting to invoke OnUserPreferenceChanged event to some other thread. I just need to know which thread it's invoking to. – JMH Mar 29 '12 at 14:48
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Regarding problems caused by SystemEvents class and in particular OnUserPreferenceChanged event try to use the CheckSystemEventsHandlersForFreeze() function in this answer which can help to find root cause, i.e. which controls was created on wrong thread and thus causing freeze.

Vlad Rudenko
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