FULL PRODUCT VERSION :
java version "1.8.0_111"
Java(TM) SE Runtime Environment (build 1.8.0_111-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.111-b14, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
ThreadMXBean.findDeadlockedThreads() fails to detect a deadlock involving ReentrantReadWriteLock. Here are the steps to reproduce the deadlock.

ReentrantReadWriteLock lock1, lock2;

- Thread A: lock1.readLock().lock();
- Thread B: lock2.readLock().lock();
- Thread C: lock1.writeLock().lock();
- Thread D: lock2.writeLock().lock();
- Thread A: lock2.readLock().lock();
- Thread B: lock1.readLock().lock();

The first 2 operations succeed. The rest of the operations cause the threads to block.

ThreadMXBean doesn't account for Thread C and D causing Thread A and B to block. Hence, ThreadMXBean doesn't report a deadlock.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Fix compiler errors in the source code by adding imports and "throws" statements. Run the code.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
bean.findDeadlockedThreads() should return a long[] of the threads involved in the deadlock. "Deadlock detected" should be printed to the screen.
ACTUAL -
Nothing is printed to the screen.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class Deadlock
{
   public static void main(String arg[])
   {
      ReentrantReadWriteLock lock1, lock2;
      ThreadMXBean bean;

      lock1 = new ReentrantReadWriteLock();
      lock2 = new ReentrantReadWriteLock();

      new Thread(() -> deadlocker(lock1, lock2)).start();
      new Thread(() -> deadlocker(lock2, lock1)).start();
      new Thread(() -> lockUnlock(lock1.writeLock())).start();
      new Thread(() -> lockUnlock(lock2.writeLock())).start();

      bean = ManagementFactory.getThreadMXBean();

      while (bean.findDeadlockedThreads() == null)
         Thread.sleep(1000);

      System.out.println("Deadlock detected");
   }

   private static void deadlocker(ReentrantReadWriteLock lock1, ReentrantReadWriteLock lock2) // TODO - Remove this
   {
      lock1.readLock().lock();
      lockUnlock(lock2.readLock());
   }

   private static void lockUnlock(Lock lock)
   {
      while (true)
      {
         lock.lock();
         lock.unlock();
      }
   }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
None found yet. I just figured out how to reproduce the deadlock and not have it detected by ThreadMXBean. I now need to write my own deadlock detector so I can figure out how to resolve my deadlock issue.