Should thread-safe class have a memory barrier at the end of its constructor?

Question

When implementing a class intended to be thread-safe, should I include a memory barrier at the end of its constructor, in order to ensure that any internal structures have c

Answer 1

In answer to your simplified question:

ConcurrentQueue queue = null;

Parallel.Invoke(
    () => queue = new ConcurrentQueue(),
    () => queue?.Enqueue(5));

It is definitely possible that your code could try to call queue.Enqueue(5) before queue has a value, but it isn't anything you could protect against from within the constructor of Queue. queue won't actually be assigned a reference to the new instance until the constructor completes.