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

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Date:	Tue, 21 Apr 2015 13:25:36 +1000
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	David Miller <davem@...emloft.net>, sowmini.varadhan@...cle.com,
	benh@...nel.crashing.org, aik@....ibm.com, anton@....ibm.com,
	paulus@...ba.org, linuxppc-dev@...ts.ozlabs.org,
	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org,
	schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
	linux-s390@...r.kernel.org, linux390@...ibm.com
Subject: Re: sparc64: Build failure due to commit f1600e549b94 (sparc: Make
 sparc64 use scalable lib/iommu-common.c functions)

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@...ck-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@...ck-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


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