Re: Linux 2.6.16.30-pre1

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

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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