I need help in design for the following situation:

There is a background handler running and catching socket messages which generates a SIGIO interrupts. This interrupt invokes a handler which looks at the data on the socket and in return calls the appropriate function for it. Now the problem is some of the datastructures used are linked lists, queues, ect.. What is best way I can prevent the interrupt from messing up the list, such as when I am deleting an item and an interrupt comes in. I think a signprocmask would work with BLOCK and UNBLOCK before and after the datastructure code. I just want to verify that sigpending would work properly espeically if more signals than just SIGIO are used.

Thanks

Don't mistake interrupts with signals. The two things are different. The interrupt will not deal with your data structures, but the signal handler will. You can use mutexes or semaphores to protect the list. But it's not a good solution, especially when you have onthread program (so the signal handler will be locked forever, because the lock will be never unlocked by the code). I recommend to modify your program in such a way that signal handlers only set certain variables. Then your program checks from time to time if the variable is set and if it is - runs a function that deals with what it needs.