linux-kernel - Re: [PATCH] x86/paravirt: revert exports to restore old behaviour

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Message-ID: <20071128204050.GA29463@stusta.de>
Date:	Wed, 28 Nov 2007 21:40:50 +0100
From:	Adrian Bunk <bunk@...nel.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tobias Powalowski <t.powa@....de>,
	Takashi Iwai <tiwai@...e.de>,
	Christoph Hellwig <hch@...radead.org>,
	Zachary Amsden <zach@...are.com>
Subject: Re: [PATCH] x86/paravirt: revert exports to restore old behaviour

On Tue, Nov 27, 2007 at 02:57:30PM -0800, Jeremy Fitzhardinge wrote:
>...
> Christoph Hellwig objects to this patch on the grounds that modules
> shouldn't be using these operations anyway.  I don't think this is a
> particularly good reason to reject the patch, for several reasons:
> 
> 1. These operations are still available to modules when not using
>    CONFIG_PARAVIRT, since they are implicitly exported as inline
>    functions via the kernel headers.  Exporting the same functionality as
>    GPL-only symbols just adds a gratuitious difference between
>    CONFIG_PARAVIRT and non-CONFIG_PARAVIRT configurations.  If we really
>    think these operations are not for module use (or non-GPL module use),
>    then we should solve the problem in a general way.

Current practice in the kernel is that when something that should not be 
done works by chance with some kernel versions and/or configurations 
that's simply an unfortunate fact that should be fixed but doesn't 
result in any guarantee that it works with all kernel versions and/or 
configurations.

> 2. It's a regression from previous kernels, which would work these
>    modules even with CONFIG_PARAVIRT enabled.
>...

It cannot be a regression since the kernel does not have a stable API 
for modules.

> Therefore, I think this patch should go in for 2.6.24.  If people
> really think that these operations should not be available to modules,
> then we can address that separately.
>...

Why should we start with one step back for getting two steps ahead?

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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