Bug 1734 - crash while refreshing devices
Summary: crash while refreshing devices
Alias: None
Product: Xamarin Studio
Classification: Desktop
Component: Android Add-in ()
Version: 2.8.1
Hardware: PC All
: High normal
Target Milestone: ---
Assignee: shana@xamarin.com
: 2561 ()
Depends on:
Reported: 2011-10-27 14:50 UTC by Sebastien Pouliot
Modified: 2012-03-20 18:53 UTC (History)
5 users (show)

Is this bug a regression?: ---
Last known good build:

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Description Sebastien Pouliot 2011-10-27 14:50:06 UTC
I clicked on "Run", "Run" and got the device/emulator dialog.

From there I could see both my emulator and Nexus S phone. Curiously I clicked "Refresh" and _lost_ my phone. A few more clicks _lost_ the simulator and another one crashed MonoDevelop.

M4A 1.9.2 on Mac OSX Lion
Comment 1 Sebastien Pouliot 2011-10-28 18:33:39 UTC
It happening again (after mba came out of sleep) and this time I got an MD dialog to show me the exception:

System.NullReferenceException: Object reference not set to an instance of an object
  at MonoDevelop.MonoDroid.AdbStartServerProcess.CaptureOutput () [0x00099] in /private/tmp/source/md-addins/MonoDevelop.MonoDroid/MonoDevelop.MonoDroid/Adb/DeviceManager.cs:446 
  at System.Threading.Thread.StartUnsafe () [0x00016] in /private/tmp/monobuild/build/BUILD/mono-2.10.6/mcs/class/corlib/System.Threading/Thread.cs:680
Comment 2 PJ 2012-01-06 16:46:18 UTC
*** Bug 2561 has been marked as a duplicate of this bug. ***
Comment 3 PJ 2012-01-06 16:58:09 UTC
Confirmed on:

MonoforAndroid 4.0.1
Mono 2.10.8
Windows 7 SP1

Unhandled exception after refreshing devices a number of times. 

System.NullReferenceException: Object reference not set to an instance of an

   at MonoDevelop.MonoDroid.AdbStartServerProcess.CaptureOutput()

   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)

   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext,
ContextCallback callback, Object state, Boolean ignoreSyncCtx)

   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext,
ContextCallback callback, Object state)

   at System.Threading.ThreadHelper.ThreadStart()

Windows Error Msg:

Problem signature:
  Problem Event Name:    CLR20r3
  Problem Signature 01:    monodevelop.exe
  Problem Signature 02:
  Problem Signature 03:    4f038baf
  Problem Signature 04:    MonoDevelop.MonoDroid
  Problem Signature 05:
  Problem Signature 06:    4f038c2d
  Problem Signature 07:    1df
  Problem Signature 08:    a5
  Problem Signature 09:    System.NullReferenceException
  OS Version:    6.1.7601.
  Locale ID:    1033
  Additional Information 1:    0a9e
  Additional Information 2:    0a9e372d3b4ad19135b953a78882e789
  Additional Information 3:    0a9e
  Additional Information 4:    0a9e372d3b4ad19135b953a78882e789

Also brought in duplicate bug from MacOSX so making this a multi-platform bug.
Comment 5 PJ 2012-02-22 15:21:35 UTC
I just reproduced this behavior on Mondevelop

Refreshing the device list repeatedly first results in this MonoDevelop output:


Continuing to do this results in a crash:

Comment 6 Alan McGovern 2012-03-02 12:14:16 UTC
I've just debugged the issue in the second gist  (https://gist.github.com/1886949) with Rodrigo and the consensus is it's a race condition between a thread abort and a null dereference. We have a workaround which is being committed to mono which should resolve the native crash permanently. I'll investigate the managed null reference exception (https://gist.github.com/a8e6e6bf7e4173714caf) now and try to get that resolved too.
Comment 7 Alan McGovern 2012-03-02 13:05:07 UTC
I think this one has been well and truly fixed now. We had missed a spot before which could still result in that null reference exception happening. I just pushed the fix for it and can verify that constant clicking on 'Refresh' does not crash MD for me anymore. Will backport it to 2.8.8-series now.
Comment 9 Alan McGovern 2012-03-20 10:46:59 UTC
Apparently the patch fixing this did not get backported from the 2-10 branch to the place where the latest 2.10.9 release came from. The commit in question is '02a2af110f4a0ffc77d75ea658baa6ddd2f5a6de'. We need a mono release with that patch in order to fix this issue for sure.
Comment 10 PJ 2012-03-20 18:53:06 UTC
I verified this fix on Mono 2.10.9 revision 8 using MD2.8.8.1 and MfA4.0.6

I can no longer crash MonoDevelop with repeated clicking of the button, although I can still get it into a non-refreshing state with an *excessive* number of rapid clicks (100).  

Change is live so I will close the bug.