public void all_and( long mask ) {
      long[] t = _t;
      for( int i=0; i<t.length; i++ ) {
        boolean done = false;
        while( !done ) {
          long old = t[i];
          done = CAS(t,i, old, old&mask );
        }
      }
      if( _next != null ) _next.all_and(mask);
      if( _sum_cache != Long.MIN_VALUE )
        _sum_cache = Long.MIN_VALUE; // Blow out cache
    }