There are many problems with this concurrent queue. Here are a few I found in a cursory reading.
In order to enqueue an element, you have to change two atomic pointers: tail->next and tail. That cannot be done atomically.
enqueue() assumes that the queue is not empty.
enqueue() happily overwrites current_tail->next even if it is not null (which may happen if some other producer has enqueued something since we read current_tail).
Then there is the old-time favourite ABA problem.
By the way, when used in a loop, compare_exchange_weak is preferred to compare_exchange_strong, and there is no need to reload the atomic every time: compare_exchange_* do that for you by updating the argument containing the expected value.
In order to enqueue an element, you have to change two atomic pointers: tail->next and tail. That cannot be done atomically.
enqueue() assumes that the queue is not empty.
enqueue() happily overwrites current_tail->next even if it is not null (which may happen if some other producer has enqueued something since we read current_tail).
Then there is the old-time favourite ABA problem.
By the way, when used in a loop, compare_exchange_weak is preferred to compare_exchange_strong, and there is no need to reload the atomic every time: compare_exchange_* do that for you by updating the argument containing the expected value.