Re: [PATCH v9 00/12] Support PPTT for ARM64

Geert Uytterhoeven
2018-05-29T17:18:40Z

Hi Robin,

On Tue, May 29, 2018 at 7:08 PM, Robin Murphy <robin.murphy@arm.com> wrote:
> On 29/05/18 16:51, Geert Uytterhoeven wrote:
>> On Tue, May 29, 2018 at 5:08 PM, Will Deacon <will.deacon@arm.com> wrote:
>>> On Tue, May 29, 2018 at 02:18:40PM +0100, Sudeep Holla wrote:
>>>> On 29/05/18 12:56, Geert Uytterhoeven wrote:
>>>>> On Tue, May 29, 2018 at 1:14 PM, Sudeep Holla <sudeep.holla@arm.com>
>>>>> wrote:
>>>>>> On 29/05/18 11:48, Geert Uytterhoeven wrote:
>>>>>>> System supend still works fine on systems with big cores only:
>>>>>>>
>>>>>>> R-Car H3 ES1.0 (4xCA57 (4xCA53 disabled in firmware))
>>>>>>> R-Car M3-N (2xCA57)
>>>>>>>
>>>>>>> Reverting this commit fixes the issue for me.
>>>>>>
>>>>>> I can't find anything that relates to system suspend in these patches
>>>>>> unless they are messing with something during CPU hot plug-in back
>>>>>> during resume.
>>>>>
>>>>> It's only the last patch that introduces the breakage.
>>>>
>>>> As specified in the commit log, it won't change any behavior for DT
>>>> systems if it's non-NUMA or single node system. So I am still wondering
>>>> what could trigger this regression.
>>>
>>> I wonder if we're somehow giving an uninitialised/invalid NUMA
>>> configuration
>>> to the scheduler, although I can't see how this would happen.
>>>
>>> Geert -- if you enable CONFIG_DEBUG_PER_CPU_MAPS=y and apply the diff
>>> below
>>> do you see anything shouting in dmesg?
>>
>> Thanks, but unfortunately it doesn't help.
>> I added some debug code to print cpumask, but so far I don't see anything
>> suspicious.
>
> Do you have CONFIG_NUMA enabled? On a hunch I've managed to reproduce what
> looks like the same thing on a Juno board with NUMA=n; going in with
> external debug it seems to be stuck in the loop in
> init_sched_groups_capacity(), with an approximate stack trace of:

CONFIG_NUMA is not set.
I'm basically using renesas_defconfig from
https://git.kernel.org/pub/scm/linux/kernel/git/horms/renesas.git/log/?h=topic/renesas-defconfig

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds