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:   Mon, 17 Jul 2017 11:51:39 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.co.uk>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        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)

Hi,

On Sun, Jul 16, 2017 at 10:59:42PM -0700, Tony Lindgren wrote:
> * Roman Gushchin <guro@...com> [170716 05:55]:
> > On Fri, Jul 14, 2017 at 07:23:43PM +0200, Sebastian Reichel wrote:
> > > 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?
> 
> Sebastian, for me droid 4 boots just fine with v4.13-rc1 +
> 19d39a3810e if that helps. So that's with commit 422580c3cea7.

v4.13-rc1 + 19d39a3810e was also broken for me. I just disabled
some unused bits in my .config and now the kernel boots with
(with 422580c3cea7 that is). Maybe I hit some maximum image size
limit for Droid 4?

Anyways it looks like 422580c3cea7 is not the actual problem
and merely reveals some other problem.

-- Sebastian

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