Tool to check global variables thread-safe protection

I have large C code base for a micro-controller. I am working开发者_运维知识库 on a task to check if all global variables are thread-safe or not.

We don't have threads, but we have interrupts (high priority interrupts can preempt low priority ones).

NOTE: I use SciTools Understand tool to make searching for global variables and their references easily. but this requires a LOT of manual searching/reading/checking.

Is there any tool which can find the global variables used in more than one call tree?

It seems there is no something ready which do this. I did a perl script which uses SciTools Understand APIs to get the shared global variables.