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Date:      Sun, 18 Dec 2011 13:53:26 +0200
From:      Kostik Belousov <kostikbel@gmail.com>
To:        Dag-Erling Sm??rgrav <des@des.no>
Cc:        arch@freebsd.org, Poul-Henning Kamp <phk@phk.freebsd.dk>, threads@freebsd.org, Ed Schouten <ed@80386.nl>
Subject:   Re: [Patch] C1X threading support
Message-ID:  <20111218115326.GD50300@deviant.kiev.zoral.com.ua>
In-Reply-To: <86ty4y4rj5.fsf@ds4.des.no>
References:  <85477.1324155737@critter.freebsd.dk> <86ty4y4rj5.fsf@ds4.des.no>

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On Sun, Dec 18, 2011 at 02:06:38AM +0100, Dag-Erling Sm??rgrav wrote:
> "Poul-Henning Kamp" <phk@phk.freebsd.dk> writes:
> > Ohhh, but I know:  Lets make a rival to the POSIX threads, we can do it
> > much better and slightly incompatible, big market there I'm sure.
>=20
> That's not the point.  The point is that C until now did not have a
> concurrency model.  The threading API in itself is not important; I'm
> sure the committee knows perfectly well that nobody is going to use it.
> What's important is that the standard now defines how C behaves in a
> concurrent environment.

Well, the reverse was exactly _my_ point. I cannot find the description of
how the abstract C machine behaves, in the presence of multiple threads
of execution. The atomics chapter covers only some special operations,
which are added in the new revision.

E.g., there is absolutely no mention of the memory changes visibility,
or guarantees of atimicity of the assignments/reads etc. IMO, the threading
was slapped nearby, and the standard is not useful as-is. I am sorry if
I missed the parts.

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