Date: Fri, 17 Oct 2008 00:55:44 -0700
From: Greg KH <greg@kroah.com>
To: Adrian Bunk <bunk@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
       linux-kernel@vger.kernel.org
Subject: Re: [RFC] Kernel version numbering scheme change
Message-ID: <20081017075544.GB4850@kroah.com>
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On Fri, Oct 17, 2008 at 09:47:51AM +0300, Adrian Bunk wrote:
> On Thu, Oct 16, 2008 at 08:47:17PM -0700, Greg KH wrote:
> > On Thu, Oct 16, 2008 at 07:46:02PM +0300, Adrian Bunk wrote:
> > > On Thu, Oct 16, 2008 at 08:17:48AM -0700, Greg KH wrote:
> > > > On Thu, Oct 16, 2008 at 03:49:43PM +0300, Adrian Bunk wrote:
> > > >...
> > > > > If a distribution will try to autobuild an urgent OpenSSL security 
> > > > > update for their stable release in a chroot on a machine running
> > > > > kernel 2009.2.3 they will surely love you for being responsible
> > > > > for this...
> > > > 
> > > > Distros properly patch things and backport "urgent OpenSSL security
> > > > updates" to older versions of packages, so they would not run into this
> > > > problem.
> > > 
> > > You didn't get my point.
> > > 
> > > Let me make an example:
> > > 
> > > The current Debian release will be supported until one year after the
> > > next release gets released.
> > > 
> > > Someone from the Debian security team send a fixed package to the
> > > buildds.
> > > 
> > > The buildds build packages in chroots.
> > > 
> > > A buildd may run any Debian release.
> > > 
> > > And it's perfectly normal that a buildd runs a more recent release of 
> > > Debian than the one a package gets built for in a chroot.
> > 
> > So you are saying the Debian build system would build a package for an
> > older release, on a system that is newer,
> 
> Packages are built in a chroot with the correct release installed.

Then why would this break if they are being built against the correct,
older, kernel?

> > and that build would be
> > determining things based on the system it is built on, not what it is
> > being built for?
> 
> No.
> 
> In the example I gave it is OpenSSL that parses the version number of 
> the kernel.

The running kernel, with the expectation that this is the kernel it is
going to be running on after it is built, right?  Sounds like to ensure
this is correct, you better be building it on the kernel that you are
going to run it on, or its build process is broken.

> > If so, then something is very broken already in the Debian build system
> > and I think you have much bigger problems to worry about right now.
> > 
> > For all other "sane" build systems that I know of, you build against the
> > libraries/kernel/gcc/glibc/etc that you are wanting to support it for,
> > not against some random-whatever-happened-to-be-installed-on-the-box.
> 
> Building in a chroot is hardly "very broken".
> 
> And it does build against the correct
> libraries/kernel headers/gcc/glibc/etc .

But not against the proper kernel it will be run on, which sounds
broken.

> Did you ever use a chroot?

There's a fine line between being condencending and asking a valid
question.  I'll assume you are not being condencending here...

Yes, of course.

> And this was just one example.
> 
> What does userspace with the kernel version returned by GDTIOCTL_OSVERS?

I don't know, hopefully not much if anything.  glibc does things with
it, but that is usually to turn off emulation of various features that
are in the kernel in newer releases.

> I don't know whether it just displays the number, or whether it 
> determines anything based on it.
> 
> Or what else might parse the version number?
> 
> What if some proprietary userspace software like Skype or Flash or 
> whatever parses the kernel version number at runtime and barfs on 
> 2009.2.3 in a way similar to the OpenSSL build system?
> 
> WHAT YOU SUGGEST WILL BREAK EXISTING USERSPACE SOFTWARE.
> 
> Please admit this fact.

"Might" I will give you, "Will", I will not without actually testing.

And hey, if it's a problem, just fix userspace reporting to always say
we are the 2.6.30 release and go on our merry way, perhaps providing
another sysctl if it's really needed (glibc probably wants it, so it
would be easy to add.)

That's just a minor technical thing that can be trivially fixed _IF_ we
decide it is something that we want to do.

And to get back to the original point, Linus had expressed such an
interest in changing this a while ago, so I was bringing it up, saying
that I to thought we should change this, and proposed one such naming
change.

That has nothing to do with the "OMG You killed SKYPE!" hysteria that
you are proposing here.  Please separate the two issues as they are
totally different.

thanks,

greg "take a chill pill" k-h
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