Changing jboss-log4j.xml caused JBoss to go unresponsive

Issue

• We made a change to the jboss-log4j.xml file and then JBoss went unresponsive.

• Many threads are stuck waiting to lock a org.apache.log4j.spi.Rootlogger.  This RootLogger is locked by the Timer-Log4jService thread, which is in a waiting state itself:

      "Timer-Log4jService" daemon prio=10 tid=0x00002aaae02e5800 nid=0x50ac in Object.wait() [0x000000004287a000]
         java.lang.Thread.State: WAITING (on object monitor)
           at java.lang.Object.wait(Native Method)
           at java.lang.Thread.join(Thread.java:1186)
           - locked <0x00000004232ca6f8> (a java.lang.Thread)
           at java.lang.Thread.join(Thread.java:1239)
           at org.apache.log4j.AsyncAppender.close(AsyncAppender.java:240)
           at org.apache.log4j.helpers.AppenderAttachableImpl.removeAllAppenders(AppenderAttachableImpl.java:140)
           at org.apache.log4j.Category.removeAllAppenders(Category.java:868)
           - locked <0x000000040f464d78> (a org.apache.log4j.spi.RootLogger)
           at org.apache.log4j.xml.DOMConfigurator.parseChildrenOfLoggerElement(DOMConfigurator.java:410)
           at org.apache.log4j.xml.DOMConfigurator.parseRoot(DOMConfigurator.java:394)
           - locked <0x000000040f464d78> (a org.apache.log4j.spi.RootLogger)
           at org.apache.log4j.xml.DOMConfigurator.parse(DOMConfigurator.java:829)
           at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:712)
           at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:618)
           at org.apache.log4j.xml.DOMConfigurator.configure(DOMConfigurator.java:743)
           at org.jboss.logging.Log4jService$URLWatchTimerTask.reconfigure(Log4jService.java:697)
           at org.jboss.logging.Log4jService$URLWatchTimerTask.run(Log4jService.java:636)
           at java.util.TimerThread.mainLoop(Timer.java:512)
           at java.util.TimerThread.run(Timer.java:462)