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https://issues.apache.org/jira/browse/OPENJPA-1993?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13029019#comment-13029019
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Jody Grassel commented on OPENJPA-1993:
---------------------------------------
Checked in the fix for this issue. To preserve original behavior, the
ContextClassLoader override will only take place if the following OpenJPA
Compatibility option is set:
openjpa.Compatibility="OverrideContextClassloader=true"
> Deadlock Potential with ORM XML Processing
> ------------------------------------------
>
> Key: OPENJPA-1993
> URL: https://issues.apache.org/jira/browse/OPENJPA-1993
> Project: OpenJPA
> Issue Type: Bug
> Components: kernel
> Affects Versions: 1.0.0, 1.0.1, 1.0.2, 1.0.3, 1.0.4, 1.2.0, 1.2.1, 1.2.2,
> 2.0.0, 2.0.1, 2.1.0
> Reporter: Jody Grassel
> Assignee: Jody Grassel
>
> There exists the potential for deadlock with the ORM XML processing function.
> In an environment
> with multiple threads (such as an application server), operations (such as
> creating a new
> EntityManagerFactory or transformation Classloader activity) can lead to a
> point where
> a Xerces SAX Parser (acquired by XMLFactory) is constituted and executed.
> Xerces calls
> Thread.currentThread().getContextClassloader() during its execution to
> construct the
> SAXParser (via ObjectFactory.createObject()). This means that within the
> call to Xerces,
> a ClassLoader lock will be attempted on the Thread's ContextClassLoader. If
> there is already
> a lock with a ClassLoader higher in the heirarchy, and another thread with a
> lock on the
> same ContextClassLoader that is waiting to acquire a lock on a higher level
> ClassLoader, then
> a deadlock will occur.
> A solution to this problem is to temporally set the Thread's
> ContextClassLoader at the
> point where XML APIs are invoked (such as in XMLFactory, XMLMetaDataParser)
> to the
> ClassLoader that loaded the OpenJPA implementation classes. This will
> prevent Xerces from
> starting with a lower level classloader and avoid this deadlock potential.
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