JBoss becomes unresponsive with threads blocking on org.apache.log4j.spi.RootLogger

Issue

• JBoss becomes slow/unresponsive with many threads blocking on org.apache.log4j.spi.RootLogger like so:

  "ajp-127.0.0.1-8009-1" daemon prio=10 tid=0x0000000062320800 nid=0x3b40 waiting for monitor entry [0x0000000045f89000]
     java.lang.Thread.State: BLOCKED (on object monitor)
      at org.apache.log4j.Category.callAppenders(Category.java:201)
      - locked <0x0000000771a28f70> (a org.apache.log4j.spi.RootLogger)
      at org.apache.log4j.Category.forcedLog(Category.java:388)
      at org.apache.log4j.Category.log(Category.java:853)
      at org.apache.commons.logging.impl.Log4JLogger.error(Log4JLogger.java:257)
  

• Threads may also lock org.apache.log4j.Logger, as seen below:

"ajp-127.0.0.1-8080-36" daemon prio=3 tid=0x0c320400 nid=0xed waiting for monitor entry [0x55349000]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at org.apache.log4j.Category.callAppenders(Category.java:201)
    - waiting to lock <0x8f07d578> (a org.apache.log4j.Logger)
    at org.apache.log4j.Category.forcedLog(Category.java:388)
    at org.apache.log4j.Category.debug(Category.java:257)