A fully lock free allocator would be a huge result by itself: you would be able to allocate from a signal handler, or having truly lock free algorithms that do not need custom allocators, or avoid deadlock prone code in tricky parts like dlclose...

But I guess this was only one part and malloc wouldn't be fully lockfree.

In any case the lockfree mallocs designs I have seen use NxN queues to shuffle buffers around, but I guess it would be unsuitable for a generic malloc.