Re: 4.9-rc1 boot regression, ambiguous bisect result

From: Ingo Molnar
Date: Thu Oct 20 2016 - 02:24:25 EST

* Dan Williams <dan.j.williams@xxxxxxxxx> wrote:

> Hi,
> I am currently unable to boot a Yoga 900 with latest mainline, but 4.8 boots.
> The symptom is a reboot before the video console is available.
> I bisected to commit 816e76129ed5 "efi: Allow drivers to reserve boot
> services forever". However, that commit is known to be broken. The
> proposed fix, commit 92dc33501bfb "x86/efi: Round EFI memmap
> reservations to EFI_PAGE_SIZE", also exhibits the reboot problem.
> During the bisect some of the stopping points landed on commits that
> caused the boot process to hang rather than cause a reboot. The
> commits that resulted in a hang are marked "git bisect skip" in this
> log:
> I'll try treating those hangs as bad bisect results and re-run the
> full bisect tomorrow. In the meantime I wonder if the bisect log
> implicates a better regression candidate?

You could also try reverts of the suspicious commits, and then, if the reverted
kernel works fine, create a more linear history by cherry-picking them in the
right order - and then be able to pinpoint the bad commit with a higher