Re: Linux

From: Willy Tarreau
Date: Sun Sep 24 2006 - 16:28:19 EST

On Sun, Sep 24, 2006 at 08:16:41PM +0200, Adrian Bunk wrote:
> 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 initially did too (gcc4), but reviewing the fixes one at a time
reassured me.

> 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.

Don't worry, at this game, we *all* get proved wrong once in a while, and
this does not imply that a bad decision was taken, but rather that it is
a complicated job and we're all humans.

> 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 ...

cf above ;-)

> > 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.

I don't personaly have problems with those cards (I don't use them at all),
I was just arguing general principles in response to Greg's comments. I
think you're already taking extreme care in what you accept, but I think
that what you're currently doing is middle way between Greg's stable policy
and what yourself would really like to do. I hope that in the end, you will
not get frustrated by refraining from merging patches you would have liked
to get, while being criticized for having merged too many.

Probably that later you will have to either maintain several other versions
(let's say 2.6.16+2.6.18) or have sort of an "enhanced" branch with more
fixes (which is easy to do with GIT).

> 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.

Hmm, don't say this publicly, you'll get people saying that it is what
they expect !

> 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.

That's what I observed till now. I just wanted to warn you about the risks
of getting hit.


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