[PATCH v2 0/9] y2038 groundwork and first steps

Philippe Gerum rpm at xenomai.org
Fri May 7 15:00:05 CEST 2021


Florian Bezdeka <florian.bezdeka at siemens.com> writes:

> On 07.05.21 13:56, Philippe Gerum wrote:
>> 
>> Philippe Gerum via Xenomai <xenomai at xenomai.org> writes:
>> 
>>> Florian Bezdeka <florian.bezdeka at siemens.com> writes:
>>>
>>>> On 06.05.21 09:08, Bezdeka, Florian via Xenomai wrote:
>>>>> On Thu, 2021-05-06 at 09:02 +0200, Philippe Gerum wrote:
>>>>>> Jan Kiszka via Xenomai <xenomai at xenomai.org> writes:
>>>>>>
>>>>>>> On 05.05.21 18:52, Jan Kiszka via Xenomai wrote:
>>>>>>>> Picking up from Philippe's queue:
>>>>>>>>
>>>>>>>> This patch series prepares the tree for the upcoming y2038 work,
>>>>>>>> converting obsolete/ambiguous time specification types to the proper
>>>>>>>> ones introduced upstream by the v5.x kernel series.
>>>>>>>>
>>>>>>>> In v2, feedback on the first round has been addressed, primarily
>>>>>>>> regarding folding fixing into the patches that need them.
>>>>>>>>
>>>>>>>> In addition, this includes 3 patches from Florian that add
>>>>>>>> sem_timedwait64 system call and a test suite for it.
>>>>>>>>
>>>>>>>
>>>>>>> Seems we have some issue on ARM ("Illegal instruction" in smokey):
>>>>>>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsource.denx.de%2FXenomai%2Fxenomai-images%2F-%2Fjobs%2F264219&data=04%7C01%7Cflorian.bezdeka%40siemens.com%7C4809653e590745bc77b008d9105dbc19%7C38ae3bcd95794fd4addab42e1495d55a%7C1%7C0%7C637558817063489934%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=eH%2FvAfRIX8ORSkqcvjrmd%2BD0s6N%2FcpKD66Ptm0c0pbc%3D&reserved=0
>>>>>>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsource.denx.de%2FXenomai%2Fxenomai-images%2F-%2Fjobs%2F264225&data=04%7C01%7Cflorian.bezdeka%40siemens.com%7C4809653e590745bc77b008d9105dbc19%7C38ae3bcd95794fd4addab42e1495d55a%7C1%7C0%7C637558817063489934%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=HWAdg9KpJhevXa97ziRGDwLzyHq5%2Fj1Yv7IBcH3uTsY%3D&reserved=0
>>>>>>
>>>>>> That one may be related to the code directing clock_gettime() either to
>>>>>> the vDSO with Dovetail, or TSC readouts via a memory mapping with the
>>>>>> I-pipe, all in libcobalt.
>>>>>
>>>>> Thanks for the hint! I will check that and report back.
>>>>
>>>> I was able to find the root cause. It's glibc syscall() vs.
>>>> XENOMAI_SYSCALLx(). I have a fix around that was already tested on some
>>>> qemu targets (arm as well as x86). I will provide it soon.
>>>>
>>>> There is still one open question to me: Why is there a special syscall
>>>> handling (userland) implemented in Xenomai? I did not fully understand
>>>> why we end up with an invalid instruction on arm, but I guess it's
>>>> because of different registers being used.
>>>>
>>>> IOW: syscall() is fine as long as you are calling Linux syscalls, but
>>>> you might run into problems (at least on arm) when trying to call
>>>> Xenomai specific ones.
>>>>
>>>
>>> I may know this one, there is an ABI change in recent glibc,
>>> specifically in the glue code for the arm unwinder, which may cause
>>> this. Turning off -fasynchronous-unwind-tables should paper over that
>>> particular issue.
>> 
>> If so, then we need to fix the Xenomai syscall prologue/epilogue
>> (possibly some CPU register now has a specific function and/or should
>> hold a particular value across calls).
>> 
>
> Any references? We did not update glibc recently (CI images are still
> using glibc from Debian 10). The smokey tests running into problems now
> are the first ones that are using the *libc syscall() function. So maybe
> it was already broken on ARM?

Not sure. First caught this with EVL after an upgrade to
gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf, when the issue
started showing up.

Some calls like pthread_cancel() would crash randomly. I still have this
issue on my todo list as I want to re-enable async tables for libevl
although this is not required anymore (unlike libcobalt).

-- 
Philippe.



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