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From "Dennis Geurts (JIRA)" <j...@apache.org>
Subject [jira] Created: (ACE-105) Deadlock on (client) RepositoryAdmin.commit()
Date Thu, 13 Jan 2011 21:34:45 GMT
Deadlock on (client) RepositoryAdmin.commit()
---------------------------------------------

                 Key: ACE-105
                 URL: https://issues.apache.org/jira/browse/ACE-105
             Project: Ace
          Issue Type: Bug
    Affects Versions: 0.8.0
            Reporter: Dennis Geurts
         Attachments: ace-roi.patch, dump.txt

During a commit of changes to the repository, I have reached a deadlock.

Basically, what happens is the following: 

The commit() action triggers a call to commit on all repository sets. This triggers a serialization
to XML of the repositories. During this action, each repository is set to busy, which eventually
sets all contained RepositoryObject to busy ( i.e. RepositoryObjectImpl.setBusy() is called).
This is where a lock is created, first on its attributes, then on its associations.

Meanwhile, based on a synchronous EventAdmin event, it is decided that a new deployment version
is required for a particular target. During this deployment creation process, it is possible
that we loop over all objects in the repository. During this process we end up in the getAssociations()
call of the same RepositoryObjectImpl, that was just set to busy. Unfortunately, this call
to getAssociations() first locks the contained associations. Then, during the equals() call,
a lock is created on the contained attributes.

This can lead to a deadlock. I will attach a threaddump that reproduces the issue. 


I propose the following patch (see attachemnt) where in the RepositoryObjectImpl.setBusy()
call the lock order is reversed.

After applying this patch locally, I have not been able to reproduce this deadlock anymore.


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