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

[Mathieu Desnoyers]

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

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