A Wait-Free Stack
I'm not sure I see what's novel about this - maybe it's a verbiage thing around "wait free," but if they're atomically updating the top pointer and linked list, there will be lock contention on writes, and similarly when marking an item popped, on reads. I suppose the contention is bounded by the number of readers or writers,  but I wouldn't consider that wait free (again, that could just be a verbiage thing). But, more to the point, this is just a slight twist on how Kafka works (stack vs log / queue, but same with the pointer holding place and a cleanup operation), I don't really see it as particularly novel...perhaps I'm missing something?