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From "Julian Sedding (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FELIX-5215) Deadlocks involving global lock
Date Mon, 14 Mar 2016 16:55:33 GMT
Julian Sedding created FELIX-5215:

             Summary: Deadlocks involving global lock
                 Key: FELIX-5215
                 URL: https://issues.apache.org/jira/browse/FELIX-5215
             Project: Felix
          Issue Type: Improvement
          Components: Framework
    Affects Versions: framework-5.4.0, framework-4.6.1
            Reporter: Julian Sedding

I have recently analyzed two thread dumps on a framework 4.6.1 with deadlocks involving the
{{FelixFrameworkWiring}} thread calling {{Felix.refreshPackages}} and another thread.

In both cases the {{FelixFrameworkWiring}} thread holds Felix' global lock in {{Felix.refreshPackages}},
the other thread holds a lock in {{HttpServiceImpl}} and {{ServiceRegistry}}, respectively.
(Note, both {{HttpServiceImpl}} and {{ServiceRegistry}} had their synchronization removed
in trunk, possibly due to similar deadlocks).

While fixing the other players in the deadlock certainly helps, I was wondering if it would
be possible to change the code inside the framework in a way that such deadlocks are no longer

I believe section 4.7.3 "Synchronization Pitfalls" in the OSGi spec talks about this situation
(quoted from v5.0.0):
Generally, a bundle that calls a listener should not hold any Java monitors. This means that
neither the Framework nor the originator of a synchronous event should be in a monitor when
a callback is initiated.


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