public boolean tryExclusiveLock(Procedure<?> proc) {
    if (isLocked()) {
      return hasLockAccess(proc);
    }
    exclusiveLockOwnerProcedure = proc;
    return true;
  }
Returns whether we should wake the procedures waiting on the lock here.
hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/LockAndQueue.java