Encountered the following deadlock:

"Finalizer" daemon prio=8 tid=3 BLOCKED
at org.jboss.logmanager.LoggerNode.getParentLogger(LoggerNode.java:142)
Local Variable: org.jboss.logmanager.LoggerNode#362
at org.jboss.logmanager.LoggerInstance.getParent(LoggerInstance.java:167)
at org.jboss.logmanager.LoggerInstance.setLevel(LoggerInstance.java:96)
Local Variable: java.util.logging.Level#2
Local Variable: org.jboss.logmanager.LogContext#1
at org.jboss.logmanager.LoggerInstance.finalize(LoggerInstance.java:204)
at java.lang.ref.Finalizer.$$YJP$$invokeFinalizeMethod(Native Method)
at java.lang.ref.Finalizer.invokeFinalizeMethod(Finalizer.java)
at java.lang.ref.Finalizer.runFinalizer(Finalizer.java:83)
Local Variable: org.jboss.logmanager.LoggerInstance#161
at java.lang.ref.Finalizer.access$100(Finalizer.java:14)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:160)
Local Variable: java.lang.ref.Finalizer#65597

"Timer-Log4jService" daemon prio=5 tid=25 WAITING
at sun.misc.Unsafe.$$YJP$$park(Native Method)
at sun.misc.Unsafe.park(Unsafe.java)
Local Variable: sun.misc.Unsafe#1
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:747)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:778)
Local Variable: java.util.concurrent.locks.AbstractQueuedSynchronizer$Node#629
Local Variable: java.util.concurrent.locks.AbstractQueuedSynchronizer$Node#630
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1114)
at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186)
Local Variable: java.util.concurrent.locks.ReentrantLock$NonfairSync#89
at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:262)
Local Variable: java.util.concurrent.locks.ReentrantLock#42
at org.jboss.logmanager.LoggerInstance.setLevel(LoggerInstance.java:89)
at org.jboss.logmanager.LoggerInstance.<init>(LoggerInstance.java:53)
Local Variable: org.jboss.logmanager.LoggerInstance#1049
Local Variable: java.lang.String#936666
at org.jboss.logmanager.LoggerNode.getOrCreateLogger(LoggerNode.java:127)
at org.jboss.logmanager.LogContext.getLogger(LogContext.java:71)
at org.jboss.logmanager.LogManager.getLogger(LogManager.java:273)
at java.util.logging.LogManager.demandLogger(LogManager.java:390)
at java.util.logging.Logger.getLogger(Logger.java:274)
Local Variable: org.jboss.logmanager.LogManager#1
at org.jboss.logbridge.LogBridgeHandler.updateLoggers(LogBridgeHandler.java:123)
Local Variable: java.util.Collections$SynchronizedMap#43
Local Variable: java.util.Vector$1#3
Local Variable: org.apache.log4j.spi.RootLogger#1
Local Variable: org.apache.log4j.Hierarchy#1
Local Variable: org.apache.log4j.Logger#375
Local Variable: java.lang.String#582052
Local Variable: org.jboss.logbridge.LevelMapper#1
Local Variable: org.jboss.logbridge.LogBridgeHandler#1
at org.jboss.logbridge.LogNotificationListener.handleNotification(LogNotificationListener.java:67)
at sun.reflect.GeneratedMethodAccessor203.invoke(<unknown string>)
Local Variable: sun.reflect.GeneratedMethodAccessor203#1
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
Local Variable: sun.reflect.DelegatingMethodAccessorImpl#458
at java.lang.reflect.Method.invoke(Method.java:597)
Local Variable: org.jboss.logbridge.LogNotificationListener#1
at org.jboss.mx.notification.NotificationListenerProxy.invoke(NotificationListenerProxy.java:153)
Local Variable: java.lang.String#2851584
Local Variable: java.lang.Object[]#760535
Local Variable: org.jboss.mx.notification.NotificationListenerProxy#2
Local Variable: java.lang.reflect.Method#16042
at $Proxy73.handleNotification(<unknown string>)
at org.jboss.mx.util.JBossNotificationBroadcasterSupport.handleNotification(JBossNotificationBroadcasterSupport.java:127)
Local Variable: $Proxy73#1
at org.jboss.mx.util.JBossNotificationBroadcasterSupport.sendNotification(JBossNotificationBroadcasterSupport.java:108)
Local Variable: org.jboss.mx.notification.DefaultListenerRegistration#3
Local Variable: org.jboss.mx.notification.ListenerRegistry$ListenerRegistrationIterator#1
at org.jboss.logging.Log4jService.emitReconfigureNotification(Log4jService.java:560)
Local Variable: org.jboss.logging.Log4jService#1
Local Variable: javax.management.Notification#1
at org.jboss.logging.Log4jService$URLWatchTimerTask.reconfigure(Log4jService.java:716)
at org.jboss.logging.Log4jService$URLWatchTimerTask.run(Log4jService.java:636)
Local Variable: org.jboss.net.protocol.resource.ResourceURLConnection#1
at java.util.TimerThread.mainLoop(Timer.java:512)
Local Variable: java.lang.Object#18446
Local Variable: org.jboss.logging.Log4jService$URLWatchTimerTask#1
Local Variable: java.util.TaskQueue#5
at java.util.TimerThread.run(Timer.java:462)

The timer thread ran logging configuration while the finalizer was processing LoggerInstance objects.

The Finalizer thread calls context.levelTreeLock.lock() in LoggerInstance.setLevel(), then enters a synchronized code block in LoggerNode.getParentLogger(). The configuration thread enters a synchronized code block in LoggerNode.getOrCreateLogger(), then creates a new LoggerInstance which calls context.levelTreeLock.lock() in LoggerInstance.setLevel().