> Bingo, that was the problem in my setup: as the patch was applied
> through a script with others, I had missed the error message about the
> conflict (I have also another conflict which can be safely ignored so
> the new one did not catch my eye)... So the patch was only
> half-applied, and the final code is broken.

> How did you solve the conflict (I am not a scheduler expert)? I can
> retry running the patched kernel with your resolution, to check if
> everything is ok.

After looking a bit more, the conflict resolution seemed straighforward,
so I gave it a go. The attached version booted fine, so the initial
problem was purely PEBCAK... Sorry for the noise!

-- 
Damien