[OE-core] [PATCH] kernel.bbclass: Fix do_shared_workdir task ordering

[Stefan Müller-Klieser]

On 11.08.2015 15:11, Bruce Ashfield wrote:
> On Tue, Aug 11, 2015 at 9:06 AM, Bruce Ashfield
> <bruce.ashfield at gmail.com> wrote:
>> On Tue, Aug 11, 2015 at 8:47 AM, Otavio Salvador
>> <otavio.salvador at ossystems.com.br> wrote:
>>> On Tue, Aug 11, 2015 at 12:23 AM, Bruce Ashfield
>>> <bruce.ashfield at gmail.com> wrote:
>>>> On Mon, Aug 10, 2015 at 11:21 AM, Stefan Müller-Klieser
>>>> <s.mueller-klieser at phytec.de> wrote:
>>>>> commit 02d0a003d60326 [kernel.bbclass: Fix race condition] has surfaced
>>>>> a bug in the generation of the shared_workdir. The task
>>>>> do_compile_kernelmodules adds the exported symbols of the kernel modules
>>>>> to the Module.symvers. By creating the shared_workdir before the modules
>>>>> are compiled, the symbols of the modules are missing in the
>>>>> shared_workdir. Subsequent external module builds will not include the
>>>>> ABI CRC of functions exported in modules. Modprobe will fail to load the
>>>>> external module if CONFIG_MODVERSIONS is enabled.\
>>>>
>>>> Have you seen our bug: https://bugzilla.yoctoproject.org/show_bug.cgi?id=8127 ?
>>>>
>>>> It's new .. so probably not.
I did not. Thanks.

>>>>
>>>> The significant issue with this, is that we are now forcing anyone
>>>> that needs the
>>>> shared workdir artifacts to build kernel modules.
That's by design. The artifacts are modified by the module build.

>>>>
>>>> That's performance issue for many workflows.
>>>>
>>>> I had some changes where I was working to short cut parts of the process, but
>>>> they turned out to miss a few corner cases.
>>>>
>>>> We need to do more thinking on this one, before we can bring in a change like
>>>> this .. since avoiding that overhead is something valuable.
So you are saying a fast build is more important than a correct build? 
That's quite a bold statement.

>>>
>>> I agree that performance is important but correctness seems more
>>> valuable for me. I think the optimization can come as a subsequent
>>> patch ...
>>
>> Let's disagree on this point.
>>
>> There's time to get this right. We have a bug to track it, so we wont'
>> release with
>> the active bug, and this only hits a very tiny set of users.
>>
>> So we are going to step back and try and fix this right.
Well, if you really want to do this then there should at least be a 
module-interdepend.bbclass not using the shared workdir and depending on 
the modules build. Fido and master are broken at the moment.

Regards,

Stefan

>
> I hit send too soon. I have a suggestion in the bug already, so it isn't like
> we are talking about letting this sit for weeks.
>
> History shows that we are very unlikely to loop back and fix the performance
> of perf or other builds once the change goes in. So in the absence of
> other concrete suggestions, looking into some other small changes is a good
> use of time.
>
> Cheers,
>
> Bruce
>
>
>>
>> Bruce
>>
>>>
>>> --
>>> Otavio Salvador                             O.S. Systems
>>> http://www.ossystems.com.br        http://code.ossystems.com.br
>>> Mobile: +55 (53) 9981-7854            Mobile: +1 (347) 903-9750
>>
>>
>>
>> --
>> "Thou shalt not follow the NULL pointer, for chaos and madness await
>> thee at its end"
>
>
>