On NT you can get this sort of stuff through WMI, although I'll admit it's not entirely clear to me how that resolves internally

I guess my point/question was more - is whatever system/library call you'd use atomic? There's technically no reason the system couldn't have a syscall that returns a full data structure of process info for as many processes as are in scope and guarantee that it's a perfect atomic snapshot of exactly how the process table looked when that call returned, but I'd want to be very confident and have explicit documentation promising as much before I depended on it.