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Date: Sun, 19 Nov 2006 15:42:15 +0100
From: Ivan Voras <ivoras@fer.hr>
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To: Julian Elischer <julian@elischer.org>
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Cc: freebsd-arch@freebsd.org
Subject: Re: [Fwd: Re: Lockless algorithms [was Re: splxxx replacements?]]
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Julian Elischer wrote:

> I don;t think that patent issues can be to much of an issue as RCU (as
> it is in my understanding) has been used in the kernel since the very
> earliest of days, even before there was SMP.
> 

> From my understanding this is RCU. (unless I'm thinking of a different
> RCU :-)

You're right, but I found this document:
http://lse.sourceforge.net/locking/rcupdate.html and it mentions the
algorithm/method was developed "for DYNIX/ptx, a UNIX operating system
from Sequent Computer Systems Inc., now a part of IBM. Similar methods
were also used for Tornado and K42 OS projects at University of Toronto
and IBM Research."

It seems to me that there's nothing to patent, since it's an obvious way
to do lock-free update, but what do I know...

I brought this up because I remembered PHK's thread on new callout
mechanism and the discussion about scaling it to MP.