Back to USA through Canada

Explore the possibility of
Go: USA --> Canada --> China.
Back China --> Canada --> USA.
without going through the time-consuming visa stamp application. The whole journey takes less than 30days, and I am a Canada permanent resident (not citizen yet).
I know that if I go to Canada and come back to USA within 30days, I don't need to submit I-94 and no visa stamp is needed. And since I am a Canada permanent resident, I don't need a visa to enter Canada from China. From legal point of view, is it OK? Anyone tried it? I am working in USA now, and don't think I can afford 2-month or even longer background check.
Thanks for your help in advance.
Synthia