IllegalMonitorStateException Thrown From Synchronized Block

Question

Greetings,
We recently had a case where a java.lang.IllegalMonitorStateException was thrown from section of code (in activemq) that I'm 99.9% sure was properly synchronized. Has anyone ever seen this exception thrown when the object whose wait method is being called is currently owened (via. a synchronized block)?
The code that this exception occurred was in the backport-util-concurrent library. A get method (which is synchronized) call was made to a FutureTask instance which (eventually) calls Object.wait(). This call threw the exception. Below is the FutureTask code.
public synchronized Object get() throws InterruptedException, ExecutionException
  waitFor();
  return getResult();
private void waitFor() throws InterruptedException
  while (!isDone())
    wait();
}And the stack trace on the exception was:
ERROR - 21/2 08:56:41 - Failed to checkpoint a message store: java.lang.IllegalMonitorStateException - org.apache.activemq.store.journal.JournalPersistenceAdapter 395
java.lang.IllegalMonitorStateException
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:485)
at edu.emory.mathcs.backport.java.util.concurrent.FutureTask.waitFor(FutureTask.java:267)
at edu.emory.mathcs.backport.java.util.concurrent.FutureTask.get(FutureTask.java:117)
at org.apache.activemq.store.journal.JournalPersistenceAdapter.doCheckpoint(JournalPersistenceAdapter.java:386)
at org.apache.activemq.store.journal.JournalPersistenceAdapter$2.iterate(JournalPersistenceAdapter.java:129)
at org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:117)
at org.apache.activemq.thread.PooledTaskRunner.access$100(PooledTaskRunner.java:26)
at org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:44)
at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650)
at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675)
at java.lang.Thread.run(Thread.java:619)We are running Java 1.6 on solaris (64-bit). If anybody has any feedback on what might have caused this problem it would be appreciated.
Thanks,
Corey

Answer 1

There seem to be some difficult to reproduce bugs in JDK 6 relating to hotspot compilation (and maybe synchronization). A few threads worth checking out:
http://forum.java.sun.com/thread.jspa?threadID=5251785&tstart=0
http://forum.java.sun.com/thread.jspa?threadID=5262404&tstart=0
My own bug report (this one is reproducible): http://www.blinkenbyte.org/jvm/hotspot_bug_reviewid_1085121.html
Which reminds me, I need to get around to submitting an update to the report.. disabling HotSpot compilation on the problematic method made the problem go away in my case...
If at all possible to turn this into a test case, please do so and submit a bug report to Sun. Somehow Sun needs to pay attention to this problem, but I haven't even got a bug id on my problem despite it being 100% reproducible.