Re: [I-PIPE] ipipe-core-4.19.165-cip41-arm64-09 released

[Philippe Gerum <rpm@xenomai.org>]

Jan Kiszka <jan.kiszka@siemens.com> writes:

> On 01.03.21 17:53, Philippe Gerum wrote:
>> 
>> Jan Kiszka <jan.kiszka@siemens.com> writes:
>> 
>>> On 25.02.21 15:18, Philippe Gerum wrote:
>>>>
>>>> Jan Kiszka <jan.kiszka@siemens.com> writes:
>>>>
>>>>> On 25.02.21 14:54, Philippe Gerum wrote:
>>>>>>
>>>>>> Jan Kiszka <jan.kiszka@siemens.com> writes:
>>>>>>
>>>>>>> On 24.02.21 12:35, Henning Schild via Xenomai wrote:
>>>>>>>> Am Wed, 24 Feb 2021 11:24:55 +0100
>>>>>>>> schrieb Henning Schild via Xenomai <xenomai@xenomai.org>:
>>>>>>>>
>>>>>>>>> Am Wed, 10 Feb 2021 12:08:43 +0100
>>>>>>>>> schrieb Jan Kiszka via Xenomai <xenomai@xenomai.org>:
>>>>>>>>>
>>>>>>>>>> On 10.02.21 11:07, Bezdeka, Florian (T RDA IOT SES-DE) wrote:  
>>>>>>>>>>> On Wed, 2021-02-10 at 09:15 +0100, Jan Kiszka via Xenomai wrote:
>>>>>>>>>>>   
>>>>>>>>>>>> On 10.02.21 07:22, xenomai--- via Xenomai wrote:    
>>>>>>>>>>>>> Download URL:
>>>>>>>>>>>>> https://xenomai.org/downloads/ipipe/v4.x/arm64/ipipe-core-4.19.165-cip41-arm64-09.patch
>>>>>>>>>>>>>
>>>>>>>>>>>>> Repository: https://git.xenomai.org/ipipe-arm64
>>>>>>>>>>>>> Release tag: ipipe-core-4.19.165-cip41-arm64-09
>>>>>>>>>>>>>    
>>>>>>>>>>>>
>>>>>>>>>>>> Hmm, now we have the 5.4-arm64 issue also on 4.19:
>>>>>>>>>>>> https://gitlab.denx.de/Xenomai/xenomai-images/-/jobs/219984
>>>>>>>>>>>>    
>>>>>>>>>>>
>>>>>>>>>>> I don't know much about the things going on here, but found this
>>>>>>>>>>> line in the log. Maybe a starting point...
>>>>>>>>>>>
>>>>>>>>>>> 2021-02-10T07:51:47 setsched.c:120, assertion failed: stats.msw ==
>>>>>>>>>>> msw   
>>>>>>>>>>
>>>>>>>>>> Exactly, that is causing the overall failure. And it was first seen
>>>>>>>>>> with the newly added 5.4 kernel.  
>>>>>>>>>
>>>>>>>>> Seing the same on amd64 when testing on qemu, real HW is fine.
>>>>>>>>>
>>>>>>>>> Managed to bisect it down to 4.19.147-cip (good) 4.19.150-cip (bad)
>>>>>>>>>
>>>>>>>>> Which also means that ipipe-core-4.19.152-cip37-x86-15 is affected.
>>>>>>>>>
>>>>>>>>> https://gitlab.denx.de/Xenomai/xenomai-images/-/jobs/200646
>>>>>>>>> did not find it, so maybe our config differs
>>>>>>>
>>>>>>> Already compared yours against the one in xenomai-images? That would be
>>>>>>> useful.
>>>>>>>
>>>>>>>>
>>>>>>>> Digging further i found 0f0b6099c45ff3e06d2487816cf1ff30d21835f6 likely
>>>>>>>> causing the problem.
>>>>>>>>
>>>>>>>> ipipe-core-4.19.152-cip37-x86-15 <- bad
>>>>>>>> revert 2b294ac325c7ce3f36854b74d0d1d89dc1d1d8b8
>>>>>>>> revert 8579a0440381353e0a71dd6a4d4371be8457eac4 <- bad
>>>>>>>> revert 0f0b6099c45ff3e06d2487816cf1ff30d <- good
>>>>>>>>
>>>>>>>> I think here Jan or Phillipe should take over.
>>>>>>>
>>>>>>> Thanks for bisecting, this is helpful!
>>>>>>>
>>>>>>> Philippe, any immediate idea why all that is failing now?
>>>>>>
>>>>>> Something may be going wrong with MAP_SHARED mappings wrt commit_vma()
>>>>>> in Dovetail. I'm adding this to my debug queue.
>>>>>>
>>>>>
>>>>> This is still I-pipe, not a dovetail-related issues.
>>>>
>>>> This I-pipe release mimics what Dovetail does wrt mm pinning.
>>>>
>>>
>>> Any news on this from your side?
>>>
>> 
>> No time slot for working on this yet. High multiplexing rate ATM.
>> 
>
> I reproduced the issue on qemu-arm64 (xenomai-images exposes it
> directly), and I'm testing a fix.
>
> Brief summary:
> Removal of un-COW support was a mistake. We will continue to require it
> because it not only affects the child (where the removal argumentation
> was targeting), but it also prevents that shared pages - even if locked
> - on a RT parent suddenly become read-only.
>
> Expect some patches later today.

The best fix is not add that ugly code back, but rather make VMA commit
code work with shared mappings.

-- 
Philippe.