Question

I have multiple preforked server processes which accept requests to modify a shared STL C++ list on a server. Each process simply pushes a new element at the end of the list and returns the iterator.

I’m not sure how should each process attempt to acquire lock on the list? Should it be on entire object or are STL Lists capable of handling concurrency since we’re just pushing an element at the end of the list?

Answer 1

The mechanism for doing this kind of synchronisation between multiple processes requires that the developer deal with several issues. Firstly whatever is being shared between the processes needs to be set up outside of them. What this usually means in practice is the use of shared memory.

Then these processes need to communicate with each other with respect to accessing the memory being shared. After all if one thread starts to work on a data structure being shared, but gets swapped out before completing the operation it will leave the data inconsistent.

This synchronisation can be done using operating system constructs such as semaphores in linux, and will allow competing processes to coordinate.

See This for linux based IPC detail
See This for Windows based IPC detail

For some reference you can use the Boost.Interprocess documentation which provides a platform independent implementation of IPC mechanisms.