Re: Linux

From: Adrian Bunk
Date: Sun Sep 24 2006 - 14:16:59 EST

On Sun, Sep 24, 2006 at 01:53:15AM +0200, Willy Tarreau wrote:
> On Sun, Sep 24, 2006 at 01:21:50AM +0200, Adrian Bunk wrote:
> > On Sat, Sep 23, 2006 at 06:56:10AM +0200, Willy Tarreau wrote:
> > > Hi Greg, Hi Adrian,
> > >
> > > On Fri, Sep 22, 2006 at 04:09:28PM -0700, Greg KH wrote:
> > >
> > > > If you want to accept new drivers and backports like this, I think you
> > > > will find it very hard to determine what to say yes or no to in the
> > > > future. It's the main problem that everyone who has tried to maintain a
> > > > stable tree has run into, that is why we set up the -stable rules to be
> > > > what they are for that very reason.
> > >
> > > When I started the 2.4-hotfix tree nearly two years ago, I wanted to
> > > avoid merging drivers changes as much as possible. And particularly,
> > > I avoided to add support for new hardware. The reason is very simple.
> > > I want to be able to guarantee that if 2.4.X works, then any 2.4.X.Y
> > > does too so that they can blindly upgrade.
> >
> > Bugfixes causing regressions are much more likely than new hardware
> > support adding regressions.
> >
> > > And if, for any reason,
> > > people suspect that 2.4.X.Y might have brought a bug, then reverting
> > > to 2.4.X.Z(Z<Y) should at most bring back older bugs but not remove
> > > previous support for any hardware.
> >
> > Either you want to use the newly supported hardware or you don't want to
> > use it.
> >
> > In any case, I don't see your point.
> The problem is when some hardware suddenly become detected and assigned
> in the middle of a stable release. Do not forget that people need stable
> releases to be able to blindly update and get their security vulnerabilities
> fixed. Sometimes, unlocking 2 SATA ports on the mobo by adding a PCI ID or
> adding the PCI ID of some new ethernet cards that were not supported may
> lead to such fun things (eth0 becoming eth2, sda becoming sdc, etc...).
> This causes real trouble to admins, particularly those doing remote
> updates. At least, I think that if you manage to inform people clearly
> enough, and to separate security fixes and such fixes in distinct releases,
> it might work in most situations. But this is a dangerous game anyway.

It seems we do not always agree. ;-)

I did consider gcc 4 support in kernel 2.4 more dangerous and you do
consider this more dangerous than I do.

I can always be proved wrong by getting reports from people that I broke
their setups. If you know someone whose setup I broke, please tell him
to inform me about this fact.

That zero feedback is good feedback is my experience since the times
when I offered packages to run kernel 2.4 on Debian 2.2, and later
packages to run kernel 2.6 on Debian 3.0 - I got almost zero feedback
except for the one time when an update removed /etc/services ...

> > > The problem with new hardware
> > > support is that it can break sensible setups :
> > >
> > > - adding a new network card support will cause existing cards to be
> > > renumberred (it happened to me on several production systems when
> > > switching from 2.2 to 2.4)
> > >
> > > - adding support for a new IDE controller can cause hda to become
> > > hdc, or worse, hda to become sda (problems encountered when adding
> > > libata support)
> >
> > I don't consider merging any patches that could cause the sda problem.
> >
> > People not using the onboard IDE controller but a different controller,
> > but OTOH having the driver for their onboard controller enabled in their
> > kernel really sounds like a strange case.
> No, this one is common, it's the reverse which is uncommon. Think about it.
> You buy a mobo, you discover that the onboard SATA is not supported, you add
> a new controller but do not disable the old one in case you have time to
> perform more tests.
> Anyway, the case above was even not that. It was simply that if the shiny
> new sata_piix driver detected the sata controller, it would then steal the
> resources first, preventing ata_piix from registering.

I know that ATA is an area that requires extra care (and I don't plan
any big updates in this area).

But having:
- two saa7134 cards in your computer and
- one of them formerly not supported and
- depending on one of them being the first one
is a case you can theoretically construct, but then there's the point
that this is highly unlikely, and OTOH the value of the added support is
more realistic.

If I was as extremely regarding regressions as you describe regarding
hardware updates, I would also have to reject any bugfixes that are not
security fixes since they might cause regressions.

I do know that the only value of the 2.6.16 tree lies in a lack of
regressions and act accordingly, but I'm trying to do this in a
pragmatic way.

> Cheers,
> Willy



"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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