Re: sparc64: Build failure due to commit f1600e549b94 (sparc: Make sparc64 use scalable lib/iommu-common.c functions)

Re: sparc64: Build failure due to commit f1600e549b94 (sparc: Make sparc64 use scalable lib/iommu-common.c functions)

[Michael Ellerman]

On Mon, 2015-04-20 at 12:50 -0400, David Miller wrote:
> From: Guenter Roeck <linux@roeck-us.net>
> Date: Mon, 20 Apr 2015 09:44:31 -0700
> 
> > On Mon, Apr 20, 2015 at 12:25:19PM -0400, David Miller wrote:
> >> From: Guenter Roeck <linux@roeck-us.net>
> >> Date: Sun, 19 Apr 2015 22:17:21 -0700
> >> 
> >> > The debug option is intended for all _other_ architectures, to
> >> > ensure that changes made for those don't break alpha/s390
> >> > builds. alpha/s390 have ARCH_NEEDS_WEAK_PER_CPU and don't need the
> >> > debug option.
> >> 
> >> Ironically this would not create a build failure for the architectures
> >> where this matters, because only powerpc has the like named percpu
> >> symbol.
> >> 
> >> So it's not really meeting the stated objective in this case.
> > 
> > Yes, that is correct; it can only find problems in non-architecture
> > code, and on the downside produces false positives and thus build errors
> > like this one.
> > 
> > Which makes the fix a bit philosophical. Rename iommu_pool_hash in
> > iommu-common, or drop DEBUG_FORCE_WEAK_PER_CPU. I would rename
> > iommu_pool_hash, but that is just me. Ultimately, I don't really
> > care one way or another, as long as the problem gets fixed.
> 
> If nightly builds of s390 and alpha, the two platforms where this
> matters, are being done as reported in this thread, then I really
> don't see the value in DEBUG_FORCE_WEAK_PER_CPU.

We do an s390 allmodconfig for every linux-next release:

  http://kisskb.ellerman.id.au/kisskb/target/573/

And also for Linus' tree:

  http://kisskb.ellerman.id.au/kisskb/target/568/

We don't have alpha allmodconfig enabled, though we could, but we do build the
defconfig:

  http://kisskb.ellerman.id.au/kisskb/target/2499/
  http://kisskb.ellerman.id.au/kisskb/target/2494/

So I think that should be sufficient to catch any percpus that are introduced
in generic code with the same name as s390/alpha variables.


> But I guess that's a more involved longer-term discussion and I guess
> I'll apply Sowmini's patches for now.

Yeah I guess it is. Thanks for merging the fix.

cheers

Re: sparc64: Build failure due to commit f1600e549b94 (sparc: Make sparc64 use scalable lib/iommu-common.c functions)

[Guenter Roeck]

On 04/20/2015 06:54 PM, Michael Ellerman wrote:
> On Mon, 2015-04-20 at 12:50 -0400, David Miller wrote:
>> From: Guenter Roeck <linux@roeck-us.net>
>> Date: Mon, 20 Apr 2015 09:44:31 -0700
>>
>>> On Mon, Apr 20, 2015 at 12:25:19PM -0400, David Miller wrote:
>>>> From: Guenter Roeck <linux@roeck-us.net>
>>>> Date: Sun, 19 Apr 2015 22:17:21 -0700
>>>>
>>>>> The debug option is intended for all _other_ architectures, to
>>>>> ensure that changes made for those don't break alpha/s390
>>>>> builds. alpha/s390 have ARCH_NEEDS_WEAK_PER_CPU and don't need the
>>>>> debug option.
>>>>
>>>> Ironically this would not create a build failure for the architectures
>>>> where this matters, because only powerpc has the like named percpu
>>>> symbol.
>>>>
>>>> So it's not really meeting the stated objective in this case.
>>>
>>> Yes, that is correct; it can only find problems in non-architecture
>>> code, and on the downside produces false positives and thus build errors
>>> like this one.
>>>
>>> Which makes the fix a bit philosophical. Rename iommu_pool_hash in
>>> iommu-common, or drop DEBUG_FORCE_WEAK_PER_CPU. I would rename
>>> iommu_pool_hash, but that is just me. Ultimately, I don't really
>>> care one way or another, as long as the problem gets fixed.
>>
>> If nightly builds of s390 and alpha, the two platforms where this
>> matters, are being done as reported in this thread, then I really
>> don't see the value in DEBUG_FORCE_WEAK_PER_CPU.

Me not either, but, as you say, that is a different discussion.

>
> We do an s390 allmodconfig for every linux-next release:
>
>    http://kisskb.ellerman.id.au/kisskb/target/573/
>
> And also for Linus' tree:
>
>    http://kisskb.ellerman.id.au/kisskb/target/568/
>
> We don't have alpha allmodconfig enabled, though we could, but we do build the
> defconfig:
>
>    http://kisskb.ellerman.id.au/kisskb/target/2499/
>    http://kisskb.ellerman.id.au/kisskb/target/2494/
>
I cover alpha:allmodconfig in my builds for -next, mainline, as well as all
kernel.org stable releases and release candidates. This discussion is a good
argument for enabling s390:allmodconfig as well.

> So I think that should be sufficient to catch any percpus that are introduced
> in generic code with the same name as s390/alpha variables.
>
Yes, but unfortunately only after the fact, though I don't see a means
to avoid that.

>
>> But I guess that's a more involved longer-term discussion and I guess
>> I'll apply Sowmini's patches for now.
>
Thanks!

Guenter

Re: sparc64: Build failure due to commit f1600e549b94 (sparc: Make sparc64 use scalable lib/iommu-common.c functions)

[Michael Ellerman]

On Mon, 2015-04-20 at 19:32 -0700, Guenter Roeck wrote:
> On 04/20/2015 06:54 PM, Michael Ellerman wrote:
> > On Mon, 2015-04-20 at 12:50 -0400, David Miller wrote:
> >> From: Guenter Roeck <linux@roeck-us.net>
> >> Date: Mon, 20 Apr 2015 09:44:31 -0700
> >>
> >>> On Mon, Apr 20, 2015 at 12:25:19PM -0400, David Miller wrote:
> >>>> From: Guenter Roeck <linux@roeck-us.net>
> >>>> Date: Sun, 19 Apr 2015 22:17:21 -0700
> >>>>
> >>>>> The debug option is intended for all _other_ architectures, to
> >>>>> ensure that changes made for those don't break alpha/s390
> >>>>> builds. alpha/s390 have ARCH_NEEDS_WEAK_PER_CPU and don't need the
> >>>>> debug option.
> >>>>
> >>>> Ironically this would not create a build failure for the architectures
> >>>> where this matters, because only powerpc has the like named percpu
> >>>> symbol.
> >>>>
> >>>> So it's not really meeting the stated objective in this case.
> >>>
> >>> Yes, that is correct; it can only find problems in non-architecture
> >>> code, and on the downside produces false positives and thus build errors
> >>> like this one.
> >>>
> >>> Which makes the fix a bit philosophical. Rename iommu_pool_hash in
> >>> iommu-common, or drop DEBUG_FORCE_WEAK_PER_CPU. I would rename
> >>> iommu_pool_hash, but that is just me. Ultimately, I don't really
> >>> care one way or another, as long as the problem gets fixed.
> >>
> >> If nightly builds of s390 and alpha, the two platforms where this
> >> matters, are being done as reported in this thread, then I really
> >> don't see the value in DEBUG_FORCE_WEAK_PER_CPU.
> 
> Me not either, but, as you say, that is a different discussion.
> 
> >
> > We do an s390 allmodconfig for every linux-next release:
> >
> >    http://kisskb.ellerman.id.au/kisskb/target/573/
> >
> > And also for Linus' tree:
> >
> >    http://kisskb.ellerman.id.au/kisskb/target/568/
> >
> > We don't have alpha allmodconfig enabled, though we could, but we do build the
> > defconfig:
> >
> >    http://kisskb.ellerman.id.au/kisskb/target/2499/
> >    http://kisskb.ellerman.id.au/kisskb/target/2494/
>
> I cover alpha:allmodconfig in my builds for -next, mainline, as well as all
> kernel.org stable releases and release candidates. This discussion is a good
> argument for enabling s390:allmodconfig as well.
> 
> > So I think that should be sufficient to catch any percpus that are introduced
> > in generic code with the same name as s390/alpha variables.
> 
> Yes, but unfortunately only after the fact, though I don't see a means
> to avoid that.

Yeah after the merge into linux-next, which I think is probably good enough for
something like this.

cheers