Deadlock with log4j

Issue

• An application experiences deadlock during a logging operation. We are using a custom Appender (JDBC Appender), and it is involved in the deadlock.

See two thread dumps below:

• Dump 1:

"EJB-Timer-2[target=jboss.j2ee:service=EJB3,jar=ebet-tipex-adapter.jar,name=TipexImporter]":  
        at java.lang.Throwable.printStackTrace(Throwable.java:461)  
        - waiting to lock <0x00007f53ecb6ed38> (a org.jboss.logging.util.LoggerStream)  
        at org.jboss.util.NestedSQLException.printStackTrace(NestedSQLException.java:137)  
        at org.jboss.util.NestedSQLException.printStackTrace(NestedSQLException.java:160)  
        at de.aaa.jboss.log4j.JDBCAppender.append(JDBCAppender.java:125)

• Dump 2:

"EntityStoreManager watchdog timer":  
        at java.lang.Throwable.printStackTrace(Throwable.java:461)  
        - waiting to lock <0x00007fb471ade298> (a org.jboss.logging.util.LoggerStream)  
        at java.lang.Throwable.printStackTrace(Throwable.java:451)  
        at de.aaa.jboss.log4j.JDBCAppender.append(JDBCAppender.java:125)