code: public void stop()
    {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
        SibTr.entry(tc, "stop");
        
      // Lock exclusively for start operations
      mpioLockManager.lockExclusive();
      started = false;
      mpioLockManager.unlockExclusive();
      
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
        SibTr.exit(tc, "stop"); 
    }
docs: Method to stop MPIO from processing any new messages.
  This will take an exclusive lock on the lock manager and change
  the started flag to false.