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Message-ID: <alpine.LNX.1.10.0901151147420.5377@jikos.suse.cz>
Date: Thu, 15 Jan 2009 11:55:01 +0100 (CET)
From: Jiri Kosina <jkosina@...e.cz>
To: Jeremy Fitzhardinge <jeremy@...p.org>
cc: Ingo Molnar <mingo@...e.hu>,
Jeremy Fitzhardinge <jeremy@...source.com>,
linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86: remove byte locks
On Tue, 13 Jan 2009, Jeremy Fitzhardinge wrote:
> > Why can't this just be somewhere in documentation? (possibly even with
> > the byte locks code as a reference).
> Because Ingo's compil-o-matic will never fail on a documentation error.
Hmm, I have always considered the "we don't accept any code that would
have zero in-kernel users" rule as a quite reasonable one, at least in
order to prevent from bloat and code getting confusing.
But apparently it's not the intention here.
> > It is IMHO just totally confusing to have a spinlock implementation that is
> > not used at all in the tree. It took me quite some time to go through this
> > until I finally figured out that this code is actually never used.
> > Currently, on first sight it might seem that byte locks are used whenever
> > CONFIG_PARAVIRT is set, which is not true.
> Well, a comment next to the code explaining the rationale probably
> wouldn't go astray.
I still strongly feel that if the only purpose of the code in kernel is
"to provide example", then it belongs to documentation.
> > And apparently even Linus got confused by this, which also tells us
> > something by itself, see [1].
> > [1] http://marc.info/?l=linux-kernel&m=123144211719754&w=2
> It tells us that Linus couldn't give a rat's arse about virtualization,
> which is just something we have to cope with ;)
I am afraid this has nothing to do with virtualization. It's simply
confusing when looking at the code.
Thanks,
--
Jiri Kosina
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