The only carry-on problem I've had in Shanghai was at the old HongQuao airport back before PVG opened. Someone was wanting me to check the backpack (it's sized to be carry-on legal) I was wearing because it was over 5kg. I of course balked at the notion of checking $3k in camera equipment. My wife (a native speaker) was able to convince them to allow it to be carried on.

I've flown the same bag through there other times without difficulty.