Good digging.
If the original RCU patents are expired, it might make more sense for the BSDs to start to use RCU, it makes things much easier in the long run, and should scale a lot better than this proposed solution.
If the original RCU patents are expired, it might make more sense for the BSDs to start to use RCU, it makes things much easier in the long run, and should scale a lot better than this proposed solution.
Odds are, they are not, it was a very specific decision to let this be a GPLv2 only patent grant, but as I haven't worked for IBM for almost a decade, I can't speak for them in any form (not that I ever could...)
Optimizations and new versions of RCU are patented as well: preemptible variations, scalability optimizations, tiny/embedded variations, and many common data structures.
However, I agree that even the most basic RCU implementation will scale far better than referencing counting for many applications.