linux-kernel - Re: Droid 4 boot failure due to 422580c3cea7 (mm/oom_kill.c: add tracepoints for oom reaper-related events)

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Date:   Sun, 16 Jul 2017 13:53:54 +0100
From:   Roman Gushchin <guro@...com>
To:     Sebastian Reichel <sebastian.reichel@...labora.co.uk>
CC:     Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tony Lindgren <tony@...mide.com>,
        Linux-Kernel <linux-kernel@...r.kernel.org>,
        Linux-OMAP <linux-omap@...r.kernel.org>
Subject: Re: Droid 4 boot failure due to 422580c3cea7 (mm/oom_kill.c: add
 tracepoints for oom reaper-related events)

On Fri, Jul 14, 2017 at 07:23:43PM +0200, Sebastian Reichel wrote:
> Hi,
> 
> On Fri, Jul 14, 2017 at 02:12:21PM +0000, Roman Gushchin wrote:
> > > On 14 Jul 2017, at 14:43, Sebastian Reichel <sebastian.reichel@...labora.co.uk> wrote:
> > > I just bisected another issue breaking boot on Droid 4. My
> > > bisect points to 422580c3cea7 (mm/oom_kill.c: add tracepoints
> > > for oom reaper-related events). It do not see any message
> > > printed to UART (with earlyprintk) once that commit is part
> > > of my image. Kernel config is below.
> 
> > This is really interesting, because this patch adds few
> > tracepoints and all of them are called from the oom code, which is
> > hopefully not a part of the boot process.
> > 
> > Can you, please, confirm, that it can be reproduced with some
> > confidence? If so, can you, please, eliminate the tracepoints
> > calls and try to reproduce the boot failure?
> 
> I can boot 9967468c0a10 ("Merge branch 'akpm' (patches from
> Andrew)") after adding
> 
>  - http://git.kernel.org/tip/19d39a3810e7032f311ef83effdac40339b9d022
>    (another issue, that breaks Droid 4 boot)
>  - a git revert of 422580c3cea7
> 
> OTOH there are strange problems. Using da16dd9785f8 + above
> two commits also works. Using b5e16170f59b + above commits
> does not work and bisection ended up in the merge commit.

Hi, Sebastian!

As commit 422580c3cea7 hasn't added any code, which is executed
during the boot process, I could imagine only two options:
1) Added code/data occasionally broke some alignment/size contraints.
2) There is another instable bug, which compromised bisect results.

Unfortunately, I can't help you with reproducing, because I haven't
necessary hardware.

Can you, please, try some older known to be good revision with
the 422580c3cea7 patch applied?

Roman