Are North Korea and Russia/China experiencing some contention in their friendship?

North Korea is tolerated by China, propped up so that millions of starving Koreans won't flood into China. The irritant value she provides to the US amuses china. China would stomp N.Korea before she would jeopardize her position as economic superpower. China won't let N. Korea act up too much. Russia has her own problems internally and won't pay much attention to N. Korea.