Deadlock on (client) RepositoryAdmin.commit()
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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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