[geotk] [JIRA] Created: (GEOTK-72) Deadlock vulnerability between ThreadedEpsgFactory and FactoryFinder

[Martin Desruisseaux (JIRA)]

Deadlock vulnerability between ThreadedEpsgFactory and FactoryFinder
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                 Key: GEOTK-72
                 URL: http://jira.geotoolkit.org/browse/GEOTK-72
             Project: Geotoolkit
          Issue Type: Bug
          Components: Referencing
    Affects Versions: 3.06, 3.05, 3.04, 3.03, 3.02, 3.01, 3.00
            Reporter: Martin Desruisseaux
            Assignee: Martin Desruisseaux
             Fix For: 3.07


When {{FactoryFinder.getCRSAuthorityFactory(...)}} is invoked extensively in a multi-thread environment, there is sometime a deadlock:

* {{AuthorityFactoryFinder.getCRSAuthorityFactory(...)}} holds a lock on {{AuthorityFactoryFinder.class}}
* {{ThreadedAuthorityFactory.availability()}} holds a lock on {{this}}
* Both of the above methods wait for the lock of the other one (indirectly, the call stack is somewhat deep).

The easy fix is to remove the {{synchronized}} statement on {{ThreadedAuthorityFactory.availability()}}, which was not strictly necessary since the method implementation was already thread-safe (provided that the {{status}} field is made volatile). The cost is that the same work may be done twice, but I don't think it will happen often in practice.

However we should take the opportunity for reducing a bit more the amount of locks, especially in {{createBackingStore()}}, because the later invoke client code that we may not control. Even in the case of Geotk implementation, the call stack is deep with recursive calls to {{FactoryFinder}}. We are safer to arrange the code in such a way that {{createBackingStore()}} is invoked outside any synchronized block.


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