Date: Sat, 24 Dec 2011 16:28:30 -0500 From: David Schultz <das@FreeBSD.ORG> To: "Alexander V. Chernikov" <melifaro@FreeBSD.ORG> Cc: glebuis@FreeBSD.ORG, freebsd-arch@FreeBSD.ORG Subject: Re: Use of RCU (read-copy-update) Message-ID: <20111224212830.GA58693@zim.MIT.EDU> In-Reply-To: <4EF5FD0E.9050500@FreeBSD.org>
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On Sat, Dec 24, 2011, Alexander V. Chernikov wrote: > Main problem: Idea is patended: > General worlds: > http://www.groklaw.net/articlebasic.php?story=20061028211523142 > Patents in PDF: > http://www.groklaw.net/pdf/IBM-835-Exhibit_522.pdf > http://www.groklaw.net/pdf/IBM-835-Exhibit_523.pdf > http://www.groklaw.net/pdf/IBM-835-Exhibit_524.pdf [...] > What can we do about this? > 1) Do nothing. > > 2) Check if there a way to write and implementation non-covered by those > patents > > 3) Determine exact conditions under which IBM permits using RCU? (maybe > ask IBM directly?) > > 4) Consider the possibility of buying license from IBM (if we can > redistribute code under BSD license after that) Negotiating or fighting patents is a messy business, so a technical solution may be easier. The ideas behind RCU are very old, so one way out is to implement one of the older out-of-patent ideas directly. In an expired patent, IBM called the idea "passive serialization." You can also find a lot of (hopefully unencumbered) research on "software transactional memory", which is a nice abstraction for a similar mechanism. (Most of the papers focus on how to do atomic read-write transactions; read-only transactions are much easier.) But be careful: If you independently invent an improvement that isn't covered by the older patent but is covered by RCU, that idea may still infringe.home | help
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