How does the 72hours visa free works for cruise travelers?

I'm flying from USA to embark a Holland America cruise from Hong Kong, then 2nd port overnight in Shanghai, then will go to S. Korea and last disembark in Japan; do I qualify for 72 hrs visa free? Do I have to do normal visa application or it is a landing visa or it means don't have to apply at all? Or cruiselines will arrange Chinese Immigration officers to stamp for cruise travelers?