title: What is "Locked ownable synchronizers" in thread dump?
body: <p>I am trying to understand what does <code>Locked ownable synchronizers</code> refer to in a thread dump?</p>
  
  <p>I started using <a href="https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/locks/ReentrantReadWriteLock.html" rel="noreferrer"><code>ReentrantReadWriteLock</code></a> have a thread in <code>WAITING</code> state, waiting for a <code>ReentrantReadWriteLock$FairSync</code> in the "locked ownable synchronizers" list of another thread in <code>WAITING</code> state (a <code>ThreadPoolExecutor</code>).</p>
  
  <p>I couldn't find much information about that. Is it some kind of locks "passed onto" the thread? I'm trying to figure out where my deadlock comes from and I can't see any thread actively locking those (i.e. no corresponding <code>- locked &lt;0x...&gt;</code> in any stack trace).</p>