Comment by mmastrac | Hacker News Reader

Comment by mmastrac | Hacker News Reader

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It must be getting close to expiry at this point -- wasn't it filed in the mid 90s?

EDIT:

I did a little digging and some calculations in the USPTO's horrible, horrible expiry calculator and the list of patents in wikipedia (which TBH, I haven't dug into to figure out how relevant they are but the list below is roughly ordered from "fundamental" to "interesting things you can do with RCU"):

http://www.google.com/patents/US5442758 -- should have expired last year

http://www.google.com/patents/US5608893 -- will expire very shortly, but is noted as "lapsed" due to non-payment of fees

http://www.google.com/patents/US5727209 -- will expire next year

https://www.google.com/patents/US6219690 -- this one will be a few more years

http://www.google.com/patents/US6886162 -- even longer

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.

Greg, if you know anybody that has some pull on these kinds of things within IBM, can you contact The FreeBSD Foundation? We might need some kind of "FreeBSD and derivative" exemption or an interpretation of the unexpired patents effects on an RCU implementation. Justin Gibbs said last time he tried to contact IBM he got directed immediately to legal staff and does not have a good contact within IBM.

Try contacting the Linux kernel RCU maintainer, he should be able to look into if IBM is willing to do this or not.

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...)

> 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.

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.

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