Atomic code block

(NS7520 NET+OS6.3) Is it possible to create atomic code execution blocks ? We are currently having problems writing to our memory mapped io. The interrupt posture remains part of that thread’s context. (Net+OS6.3 documentation) We can’t just disable the interrupts, execute our atomic code block and re-enable the interrupts. We have to make shure the executing thread remains the executing thread (elevate his priority) to avoid re-enablement of the interrupts during execution of our atomic block. Is there an other way to create atomic code blocks ???