code: private void takeCloseLock()
     {
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc, "takeCloseLock");
  
        while (true)
        {
           try
           {
              closeLock.readLock().lockInterruptibly();
              break;
           }
           catch (InterruptedException e)
           {
              // No FFDC code needed.
           }
        }
  
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "takeCloseLock");
     }
docs: Take a "reader" lock on the close synchronization primative.