如何在彼此依赖的C文件中定义pthread和互斥锁？

I’m new to pthread and mutex lock. I used them before but in a single file (main.c that creates the threads and locks are in the same file as functions and memory that use the locks). How to define mutex lock in C files that depend on each other? Ideally, I wish not to change the current structure. I’m new to pthread and mutex lock. I used them