Re: The missing membar_X() directive

[Jean-Yves Migeon <jeanyves.migeon%free.fr@localhost>]

On 14.07.2010 21:48, der Mouse wrote:
>> IIRC, you cannot implement RCU in non GPL software (unless IBM gives
>> approval for it).
> 
> Why not?

I remember vaguely a debate where some project (non GPL) wanted to
implement a userland version of RCU, but was struck by this "GPL code
protected by patent" thing.

> Even if it's patented, it's unlikely to be patented anywhere but the
> USA (certainly the Wikipedia page gives no reason to think so); there's
> no reason the rest of the world should have to suffer the
> boneheadedness the USA has chosen to impose on itself.
>
> Since NetBSD is a USA entity, there _is_ a reason for NetBSD to put up
> with the USA's idiocies, but I see no reason someone in the sane world
> can't implement it and make patches (to NetBSD or anything else)
> available.

Sure. My remark was not NetBSD's specific.

Keep in mind that the implementation being biased towards GPL, you get
all the benefits of the licence, including its virality. As it concerns
routing code, this may as well propagate to the rest of the network
stack (which is not necessarily GPL).

> I suspect the USA patent is invalid, too, though (especially given its
> date) it's unlikely anyone with deep enough pockets to take it on
> cares.

Well, given that the patent in question comes from IBM, I am sure the
pockets are deep enough.

Such things can just be a royal pain for a project, whatever the
validity of software patents could be.

FWIW, there is some notes about it in Linux:

http://lxr.linux.no/linux+v2.6.34.1/Documentation/RCU/RTFP.txt

As rmind@ noted, passive serialization patent lapsed.

-- 
Jean-Yves Migeon
jeanyves.migeon%free.fr@localhost