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

From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Guenter Roeck <groeck@google.com>,
	Kees Cook <keescook@chromium.org>, kernelci <kernelci@groups.io>,
	Guillaume Tucker <guillaume.tucker@collabora.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>, Mark Brown <broonie@kernel.org>,
	Tomeu Vizoso <tomeu.vizoso@collabora.com>,
	Matt Hart <matthew.hart@linaro.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Kevin Hilman <khilman@baylibre.com>,
	Enric Balletbo i Serra <enric.balletbo@collabora.com>,
	Nicholas Piggin <npiggin@gmail.com>,
	linux <linux@dominikbrodowski.net>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Adrian Reber <adrian@lisas.de>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-mm <linux-mm@kvack.org>,
	Richard Guy Briggs <rgb@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>, info <info@kernelci.org>
Subject: Re: next/master boot bisection: next-20190215 on beaglebone-black
Date: Tue, 16 Apr 2019 16:05:52 -0400 (EDT)	[thread overview]
Message-ID: <2054840174.2796.1555445152616.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <CAPcyv4gxk9xbsP3YSKzxu5Yp9FTefyxHc6xC33GwZ3Zf9_eeKA@mail.gmail.com>

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

> On Thu, Apr 11, 2019 at 1:54 PM Guenter Roeck <groeck@google.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