linux-kernel - Re: [GIT PULL] Namespace file descriptors for 2.6.40

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Message-ID: <20110525131746.GA19118@elte.hu>
Date:	Wed, 25 May 2011 15:17:46 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Valdis.Kletnieks@...edu,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Linux Containers <containers@...ts.osdl.org>,
	netdev@...r.kernel.org
Subject: Re: [GIT PULL] Namespace file descriptors for 2.6.40


* Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

> On Wed, May 25, 2011 at 14:47, Ingo Molnar <mingo@...e.hu> wrote:
> > * Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> >
> >> > But at least the primary, 'native' syscall table of every arch
> >> > could be kept rather fresh via generic enumeration.
> >>
> >> So we can start all over at offset 501 (alpha just started using
> >> 500) with a unified, clean, and compressed list of syscalls? Or do
> >> we have some more other-os-compat syscalls around in this range?
> >
> > No, that would leave a big hole in the syscall table of most
> > architectures.
> 
> Sure, but we could (a) optimize for the case where the syscall number is
> larger than 500 and/or (b) drop support for syscall numbers smaller than
> 501, depending on a config option.

Dunno why there is so much desire to complicate and break 
well-working ABIs while we have a 14+ MLOC kernel with so much code 
in it that is in dire need to be improved! :-)

Yes, we can reduce the syscall addition pain via the 
ARCH_SYSCALLS_BASE trick, but we should really forget about 
*removing* (or reordering) syscall numbers as the advantages are 
marginal at best while the disadvantages are huge.

Messy syscall tables are irreversibly ingrained in tens of millions 
of systems and there's nothing we can do about that. We can improve 
the future shape of syscall tables and we can try not to make new 
mistakes, and that's a large enough job in itself ;-)

Thanks,

	Ingo
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