[RFC] Moving Intrepid to 2.6.27 kernel

[Matt Zimmerman]

On Wed, Aug 20, 2008 at 04:02:47PM -0400, Ben Collins wrote:
> As many of you know, we've continued a tree called ubuntu-next which is
> currently following 2.6.27 upstream kernel. It has been kept in sync
> with intrepid's 2.6.26 based kernel tree.

I have been in all-day meetings this past week and did not see this thread
until now.  I think this change requires stronger justification than I've
seen so far.

> In recent weeks it has become apparent that we will need several updates
> to 2.6.26 in order to have a stable kernel for 8.10. These include:
> 
>  * Updated mac80211, which will require updated wlan drivers in order 
>    to fix major regressions with suspend/resume and wlan devices.
>  * Updated alsa-1.0.17 drivers for new codecs
>  * xen64 paravirt
>  * Updated KVM
> 
> These are just the major things we need to do.

Why are these needed in order to have a stable kernel for 8.10?  Major
updates are the opposite of stability.  What we want is a kernel which fixes
more bugs than it introduces while introducing the most important driver
updates we need for the release.

> The good thing is, all of this is already in 2.6.27, and is ready to be
> uploaded on a moments notice. It has been tested by myself for quite some
> time, and others on the team have also tested it.

The amount of testing it has received is trivial compared to what 2.6.26 has
seen.  It's been tested on our certified systems and by many thousands of
community members on their own hardware.  The fact that it's been smoke
tested by a few people doesn't give me much confidence that it's free of
serious regressions.

> Yesterday, we discussed the possibility of moving to 2.6.27 before
> feature freeze on #ubuntu-kernel during out weekly IRC meeting. In
> attendance were the kernel team, Steve Langasek, Chuck Short and Soren
> Hansen. Soren and Chuck gave particularly good reasons for moving to
> 2.6.27, which included xen64 and updated KVM.

Where can I find the summary and log of the meeting?

> Steve had questions about the particulars of this move, and I believe we
> answered all of his questions satisfyingly, but we agreed to take this
> to a wider audience before making a commitment.
> 
> So fire away with any concerns or issues that this might cause. If we
> are going to do it, it needs to be decided by early next week.

I was in meetings all week and didn't see this until now.  Mario has raised
a concern in this thread which I think needs to be addressed.  I also have
the following questions:

What are the known regressions from 2.6.26 to 2.6.27?

Which systems has 2.6.27 been tested on?  What test plan was followed?

In which areas are further regressions to be expected in 2.6.27 (which parts
of the kernel have changed in the most significant ways)?

What were the results of certification testing with 2.6.27?

-- 
 - mdz