[Helma-user] java.util.ConcurrentModificationException on app.addRepository

[Hannes Wallnoefer]

2008/7/17 Burghard Britzke <bubi at charmides.in-berlin.de>:
>
> Am 17.07.2008 um 13:22 schrieb Hannes Wallnoefer:
>
>> 2008/7/17 Bernhard Fröhlich <decke at bluelife.at>:
>>>> Hello list,
>>>>
>>>> we load our widgets on helma start with app.addRepository and
>>>> sometimes we
>>>> get the following error code:
>>>>
>>>> ...
>>>> [2008/07/17 11:19:23] [ERROR] null:
>>>> java.util.ConcurrentModificationException
>>>> ...
>>>> the error is reproduceable on some machines (windows, linux) under
>>>> helma1.6.0 and helma 1.6.2, java1.6.0_01 and java1.6.0_06. it
>>>> seems to be
>>>> a
>>>> racing condition?
>>>
>>>
>>> I am not familiar with the Helma code but as far as i can tell
>>> there seems
>>> to be a missing synchronisation in
>>> TypeManager.java:checkRepositories()
>>> because the Iterator is not protected from getting invalid.
>>>
>>> So it seems like an helma bug - would you mind creating an bugreport?
>>
>> Yes, it's definitely a helma bug, so please file a bug report.
>>
>> I'm not sure just adding synchronization would help, as it could be
>> the same thread inserting into the prototype map, or synchronization
>> could result in  a deadlock. It's probably worth a try, though.
>>
>> hannes
>>
>>> Bernhard Fröhlich
>
> ConcurrentModificationExceptions can be preventet by adding proper
> synchronization

not if the collection is modified by the same thread using the iterator.

> deadlocks can be prevented by accessing the resources in the same
> sequence for each thread.

If only that was so simple as it sounded!

hannes

> sincerely,
> burghard.
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