Deadlock when shutting down

Karaf sometimes hangs while shutting down, and a thread dump shows a deadlock in DOSGi. In general, the OSGi specs recommend not to hold any locks when calling the APIs since it can result in a deadlock, as is the case here.

A proposed fix calls ServiceRegistration.unregister outside of the synchronized block in ImportRegistrationImpl.close (note that it still is synchronized when called from closeAll, which may pose a related but separate problem - but the fix does fix this specific deadlock as it was encountered here).

Found one Java-level deadlock:
=============================
"pool-18-thread-3":
waiting to lock monitor 0x00007f0658003f40 (object 0x00000000e5b485b0, a org.eclipse.osgi.internal.serviceregistry.ServiceUse),
which is held by "Blueprint Extender: 2"
"Blueprint Extender: 2":
waiting to lock monitor 0x00007f0654002a50 (object 0x00000000f1b70240, a org.apache.cxf.dosgi.dsw.service.ImportRegistrationImpl),
which is held by "pool-18-thread-3"

Java stack information for the threads listed above:
===================================================
"pool-18-thread-3":
at org.eclipse.osgi.internal.serviceregistry.ServiceRegistrationImpl.releaseService(ServiceRegistrationImpl.java:562)

• waiting to lock <0x00000000e5b485b0> (a org.eclipse.osgi.internal.serviceregistry.ServiceUse)
  at org.eclipse.osgi.internal.serviceregistry.ServiceRegistrationImpl.unregister(ServiceRegistrationImpl.java:245)
  at org.apache.cxf.dosgi.dsw.service.ImportRegistrationImpl.instanceClosed(ImportRegistrationImpl.java:118)
• locked <0x00000000f1b70240> (a org.apache.cxf.dosgi.dsw.service.ImportRegistrationImpl)
  at org.apache.cxf.dosgi.dsw.service.ImportRegistrationImpl.close(ImportRegistrationImpl.java:100)
• locked <0x00000000f1b70240> (a org.apache.cxf.dosgi.dsw.service.ImportRegistrationImpl)
  at org.apache.cxf.dosgi.topologymanager.importer.TopologyManagerImport.unexportNotAvailableServices(TopologyManagerImport.java:227)
  at org.apache.cxf.dosgi.topologymanager.importer.TopologyManagerImport.access$200(TopologyManagerImport.java:53)
  at org.apache.cxf.dosgi.topologymanager.importer.TopologyManagerImport$2.run(TopologyManagerImport.java:201)
• locked <0x00000000ea71b6c0> (a java.util.HashMap)
• locked <0x00000000ea71b6f8> (a java.util.HashMap)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
  at java.lang.Thread.run(Thread.java:722)

"Blueprint Extender: 2":
at org.apache.cxf.dosgi.dsw.service.ImportRegistrationImpl.closeAll(ImportRegistrationImpl.java:127)

• waiting to lock <0x00000000f1b70240> (a org.apache.cxf.dosgi.dsw.service.ImportRegistrationImpl)
  at org.apache.cxf.dosgi.dsw.service.ClientServiceFactory.remove(ClientServiceFactory.java:110)
  at org.apache.cxf.dosgi.dsw.service.ClientServiceFactory.ungetService(ClientServiceFactory.java:104)
• locked <0x00000000f1b6f7e0> (a org.apache.cxf.dosgi.dsw.service.ClientServiceFactory)
  at org.eclipse.osgi.internal.serviceregistry.ServiceUse$2.run(ServiceUse.java:238)
  at java.security.AccessController.doPrivileged(Native Method)
  at org.eclipse.osgi.internal.serviceregistry.ServiceUse.ungetService(ServiceUse.java:236)
  at org.eclipse.osgi.internal.serviceregistry.ServiceRegistrationImpl.ungetService(ServiceRegistrationImpl.java:518)
• locked <0x00000000e5b485b0> (a org.eclipse.osgi.internal.serviceregistry.ServiceUse)
  at org.eclipse.osgi.internal.serviceregistry.ServiceRegistry.ungetService(ServiceRegistry.java:510)
  at org.eclipse.osgi.framework.internal.core.BundleContextImpl.ungetService(BundleContextImpl.java:636)
  at org.apache.aries.blueprint.container.ReferenceListRecipe$ServiceDispatcher.destroy(ReferenceListRecipe.java:197)
• locked <0x00000000e5bab728> (a org.apache.aries.blueprint.container.ReferenceListRecipe$ServiceDispatcher)
  at org.apache.aries.blueprint.container.ReferenceListRecipe.untrack(ReferenceListRecipe.java:147)
• locked <0x00000000eaef82d0> (a java.lang.Object)
  at org.apache.aries.blueprint.container.AbstractServiceReferenceRecipe.serviceRemoved(AbstractServiceReferenceRecipe.java:370)
  at org.apache.aries.blueprint.container.AbstractServiceReferenceRecipe.access$200(AbstractServiceReferenceRecipe.java:72)
  at org.apache.aries.blueprint.container.AbstractServiceReferenceRecipe$3.run(AbstractServiceReferenceRecipe.java:324)
  at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
  at java.util.concurrent.FutureTask.run(FutureTask.java:166)
  at org.apache.aries.blueprint.container.ExecutorServiceWrapper.run(ExecutorServiceWrapper.java:106)
  at org.apache.aries.blueprint.utils.threading.impl.DiscardableRunnable.run(DiscardableRunnable.java:48)
  at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
  at java.util.concurrent.FutureTask.run(FutureTask.java:166)
  at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:178)
  at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:292)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
  at java.lang.Thread.run(Thread.java:722)

Found 1 deadlock.