[Mono-list] Patch for GC_stop_world bug in Android apps

Koushik Dutta koush at koushikdutta.com
Thu Oct 14 06:02:09 EDT 2010

I think I sent this email to the wrong list. Sorry for the duplicate:

Hey guys, thanks for taking my earlier patch that fixes garbage collection
in multithreaded apps!

Debugging threads on Android is currently broken due to the same underlying
issue. Currently the debugger will exhibit some very strange behavior when
attempting to debug a thread, and eventually hang the process. I was able to
reproduce the same problem in my parallel project which I've been
maintaining. Here is the patch to fix the debugger agent (and another
pthread_kill related issue which I haven't been able to find a bug for yet):


Submitted under the terms of the MIT/X11 license.


On Fri, Oct 1, 2010 at 9:31 AM, Koushik Dutta <koush at koushikdutta.com>wrote:

> I submit this patch under the terms of the MIT/X11 license
> On Fri, Oct 1, 2010 at 7:12 AM, Geoff Norton <gnorton at novell.com> wrote:
>> Koush,
>>   Nice, can you please confirm on the list that you're willing to
>> contribute this patch under the terms of the MIT/X11 license?
>> Thanks
>> -g
>> On 2010-09-30, at 12:26 AM, Koushik Dutta wrote:
>> Here is the fix for the following bug:
>> https://bugzilla.novell.com/show_bug.cgi?id=633454
>> The underlying problem is there is a bug in Android's libc, where after a
>> process forks, the kernel id of the forked thread is not changed to reflect
>> the new child thread. The pthread kernel id still points to the kernel id of
>> the parent process: zygote.
>> This bug breaks all multithread monodroid apps (as well as my mono on
>> Android port), as Garbage Collection fails and the process hangs.
>> The fix/workaround for the bug in Android is as follows:
>> The GC_Thread structure on Android has a new "kernel_id" member. When
>> GC_new_thread is called, the kernel id is also retrieved and stored with
>> gettid. When the world needs to be stopped/started, a new function
>> android_thread_kill is called, which is a reimplementation of Android's
>> pthread_kill. Instead, which takes the correct kernel id, rather than the
>> potentially hosed pthread.
>> I have attached a patch file, as well as committed to my fork of mono on
>> Github:
>> http://github.com/koush/mono/commit/414aff5598a2dea618741bea714fa8dd1baf0d52
>> <pthread_android.patch>_______________________________________________
>> Mono-list maillist  -  Mono-list at lists.ximian.com
>> http://lists.ximian.com/mailman/listinfo/mono-list
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