I thought as well, but, when I wrote that impl there was no way to shortcut the 2 releases into a single atomic operation. That ended up creating forks or loosing blocks.
I tested that model and a few variations with loom (https://docs.rs/loom/latest/loom/), so I'm confident that it didn't work. However, I also think that a working design might exist. I just haven't found it yet :)
Another option that makes appends cheaper would be to use a Treiber stack (one acquire, one release!), but maintain a separate path for readers. When pushing, do a read (acquire) of the tail, then set (relaxed) a back link on the second-from-top element pointing to the current top, then CAS (release) to push your node. Since the back link will always write the same value, it's ok for contending writers to submit racing writes.
Readers start by reading the tail(acquire) and storing a pointer to the node before it. They then traverse from head until they reach the node before the tail, then skip reading its back link pointer (as they already know it will point to the tail).
> append your node using CAS(release)
> update the tail pointer with CAS (release).
I thought as well, but, when I wrote that impl there was no way to shortcut the 2 releases into a single atomic operation. That ended up creating forks or loosing blocks.
I tested that model and a few variations with loom (https://docs.rs/loom/latest/loom/), so I'm confident that it didn't work. However, I also think that a working design might exist. I just haven't found it yet :)