Antonio Vargas <[EMAIL PROTECTED]> wrote: > On 11/18/06, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: >> Bill Huey (hui) <[EMAIL PROTECTED]> wrote: >> > >> > There are patent issues and the GPL license, but this is just too powerful >> > an >> > algorithm to ignore. In many way, this brings out the ultimate in what >> > shared >> > memory system can do. >> >> >> Without entering such troll subjects, the patent issue completely kills using >> RCU outside of Linux. RCU is patented IBM with special licence to use in >> Linux >> only, as far as i remember. Due to the history of IBM it would be suicidal
> Linux-only doesn't exist per-se, since linux is GPL and any GPL code > can be remixed without problems. So, the question would be if it's ok > to remix GPL with DFBSD license (which probably doesn't) Indeed you are right, RCU patent has been licensed by IBM to use in GPL code only. Hence any GPL OS can use it, but the BSDs certainly cannot, and no more Solaris. In practice, only Linux can make use of it, which was obviously IBM intent. Note this is a patent question, not a copyright question so you cannot work around it by rewriting it. To check that, i have googled a little bit and found some comments by proeminent Linux developers who were not very convinced of the performance gain associated with RCU. Of course the reads are lockless, but from time to time you have to update, and the penality is heavy. Once more, Solaris succeeds in having very good SMP scalability and excellent threading behavior without using any of these tricks. Fine grained locking needs a lot of polishing to work fine, but when everything is in good shape, it works. -- Michel Talon
