linux-kernel - Re: next/master boot bisection: next-20190215 on beaglebone-black

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Message-ID: <2054840174.2796.1555445152616.JavaMail.zimbra@efficios.com>
Date:   Tue, 16 Apr 2019 16:05:52 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Guenter Roeck <groeck@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        kernelci <kernelci@...ups.io>,
        Guillaume Tucker <guillaume.tucker@...labora.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Mark Brown <broonie@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Matt Hart <matthew.hart@...aro.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Kevin Hilman <khilman@...libre.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Nicholas Piggin <npiggin@...il.com>,
        linux <linux@...inikbrodowski.net>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Adrian Reber <adrian@...as.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-mm <linux-mm@...ck.org>,
        Richard Guy Briggs <rgb@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>, info <info@...nelci.org>
Subject: Re: next/master boot bisection: next-20190215 on beaglebone-black

----- On Apr 16, 2019, at 2:54 PM, Dan Williams dan.j.williams@...el.com wrote:

> On Thu, Apr 11, 2019 at 1:54 PM Guenter Roeck <groeck@...gle.com> wrote:
> [..]
>> > > Boot tests report
>> > >
>> > > Qemu test results:
>> > >     total: 345 pass: 345 fail: 0
>> > >
>> > > This is on top of next-20190410 with CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> > > and the known crashes fixed.
>> >
>> > In addition to CONFIG_SHUFFLE_PAGE_ALLOCATOR=y you also need the
>> > kernel command line option "page_alloc.shuffle=1"
>> >
>> > ...so I doubt you are running with shuffling enabled. Another way to
>> > double check is:
>> >
>> >    cat /sys/module/page_alloc/parameters/shuffle
>>
>> Yes, you are right. Because, with it enabled, I see:
>>
>> Kernel command line: rdinit=/sbin/init page_alloc.shuffle=1 panic=-1
>> console=ttyAMA0,115200 page_alloc.shuffle=1
>> ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 0 at ./include/linux/jump_label.h:303
>> page_alloc_shuffle+0x12c/0x1ac
>> static_key_enable(): static key 'page_alloc_shuffle_key+0x0/0x4' used
>> before call to jump_label_init()
> 
> This looks to be specific to ARM never having had to deal with
> DEFINE_STATIC_KEY_TRUE in the past.
> 
> I am able to avoid this warning by simply not enabling JUMP_LABEL
> support in my build.

Looking into this some more, it looks like I was on the wrong track
with my large branch offset theory. Is it just possible that
page_alloc_shuffle() ends up using jump labels before they are
initialized ? Perhaps this has something to do with how early
the page_alloc.shuffle=1 kernel parameter is handled.

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com