std::mutex in shared memory not working

Question

I have a scenario where the shared memory area is exclusively accessed by two different processes. When I launch the processes, the first process successfully locks the mute

Answer 1

An std::mutex instance is only scoped to a single process; it is not capable of interprocess synchronization/concurrency. It is only capable of synchronizing child threads within a parent process.

Look to use Boost or an interprocess synchronization library instead.