Bug#594967: Bug #594967: [poulsbo] grub-pc Hangs After "Welcome to GRUB!"

[Colin Watson]

On Sat, Jan 01, 2011 at 06:35:52PM -0500, P. J. McDermott wrote:
> Considering the machines this is affecting (machines with the Poulsbo
> chipset) and the configuration workaround, I'd bet the issue lies in the
> video subsystem. So far, the changes in the video/ directory appear to
> be mostly code re-factoring, so I think my next step will be to add some
> debugging output to 20100702-1's kernel and see where GRUB hangs up or
> what isn't being done. Don't expect any miracles though, as this is my
> first time in the GRUB 2 code. ;) If anyone has any thoughts on what the
> problem might be or familiarity with the GRUB kernel's initialization of
> the video subsystem, that would be helpful.

I think (with respect) that Vladimir was mistaken when he said that the
video changes in 20100702-1 only affected the EFI port.

One effect of these changes was to load the video_cirrus and video_bochs
modules by default (you can test whether this is the culprit by
commenting them out in grub.cfg).  I've seen a handful of systems that
hang while trying to enumerate the PCI bus in GRUB; it so happens that
those are the only modules that usually trigger GRUB's PCI bus
enumeration in normal circumstances ...

You can also verify this at a lower level by trying 'lspci' at a GRUB
prompt.  If it's the same problem, this will hang.

Unfortunately, I haven't had my hands on an affected machine for more
than a day or so, and that was when I was under deadline pressure so a
workaround was the best I could manage.  Steve, is your affected system
at home?  Maybe I could visit at some point (for others on the bug,
we're in the same city) ...

I've been meaning to post this hint to this bug for a while now, not to
mention trying to figure out what's actually going on rather than merely
a workaround.  Thanks for providing a nudge.

-- 
Colin Watson                                       [cjwatson at debian.org]