code: private boolean sLockable(Lockers lks, long txNum) {
  		return (!xLocked(lks) || hasXLock(lks, txNum))
  				&& (!sixLocked(lks) || hasSixLock(lks, txNum))
  				&& (!ixLocked(lks) || isTheOnlyIxLocker(lks, txNum));
  	}
docs: /*
  Verify if an item is lockable to a tx.