Question

I have a thread push-backing to STL list and another thread pop-fronting from the list. Do I need to lock the list with mutex in such case?

Answer 1

From SGI’s STL on Thread Safety:

If multiple threads access a single container, and at least one thread may potentially write, then the user is responsible for ensuring mutual exclusion between the threads during the container accesses.

Since both your threads modify the list, I guess you have to lock it.