Potential deadlock between Bundle.stop() and BundleContext.registerService()
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Key: FELIX-911
URL: https://issues.apache.org/jira/browse/FELIX-911
Project: Felix
Issue Type: Bug
Components: Framework
Affects Versions: felix-1.4.1, felix-1.4.0, felix-1.2.2, felix-1.2.1
, felix-1.2.0, felix-1.0.4, felix-1.0.3, felix-1.0.1, felix-1.0.0, felix-1.6.0
Reporter: Felix Meschberger
Fix For: felix-1.6.0
When a bundle tries to register a service (in thread T1) and the framework is
at the same time stopping the bundle (in thread T2), it may be that thread T2
holds the bundle's lock. T1 trying to register the service is thus blocked
since it cannot get the bundle lock.
This may cause a deadlock in Felix SCR, which also works with synchronized
instances: T1 may be SCR Actor thread starting a component and registering a
service and thus holding a lock on the component instance. T2 may be the
StartLevel service trying to stop the bundle, which causes the SCR to
immediately stop the component. Since the component is locked by T1, T2 cannot
acquire the lock. But since T2 already has the bundle lock, T1 cannot continue.
The problem is, that in this concrete case it is the Component's activate()
method which registers the service and not the SCR ComponentManager (the latter
deadlock situation has been taken care of in FELIX-384).
Looking at the code of Felix.registerService it looks like we could check for
the bundle state before holding the bundle lock (and we could recheck after
the lock just to be sure, if needed) and thus prevent the deadlock situation.
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