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@xxxxxxxxxxxx>
> > 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@xxxxxxxxxxxx>
> > > > 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

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