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

On 04/19/2015 08:01 PM, Michael Ellerman wrote:
> On Sun, 2015-04-19 at 14:36 -0400, Sowmini Varadhan wrote:
>>> On (04/19/15 14:09), David Miller wrote:
>>>> On (04/18/15 21:23), Guenter Roeck wrote:
>>>>> lib/built-in.o:(.discard+0x1): multiple definition of
>>>>> `__pcpu_unique_iommu_pool_hash'
>>>>> arch/powerpc/kernel/built-in.o:(.discard+0x18): first defined here
>>>>> .. I get a similar failure in the
>>>>> powerpc:allmodconfig build
>> :
>>> Maybe ping the powerpc folks becuase if they can do a quick
>>> conversion, this change isn't necessary.
>> linuxppc-dev,
>> The disussion above []
>> is in reference to the issue that Guenter Roeck
>> identified. The problem is that we have a
>> static DEFINE_PER_CPU(unsigned int, iommu_pool_hash);
> It's static ..

>> if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is configured, which is the case here.
>> The marked line above shows that __pcpu_unique_iommu_pool_hash is declared as
>> global variable"
> OK, so why doesn't CONFIG_DEBUG_FORCE_WEAK_PER_CPU depend on s390 and/or alpha?
The idea is to ensure that per cpu variable names are unique, even if static,
because that is what is needed for s390 and alpha.

> Someone needs to be doing s390/alpha builds with that enabled anyway, because
> otherwise a clash between generic code and s390/alpha won't be caught.
> Or if that's too hard we can rename the powerpc version, but it seems silly to
> rename a powerpc variable to deal with a debug option that is only useful for
> s390/alpha.

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.

Sowmini's patch would change the variable name in the lib/ code. But that was
not the question here. The question was if the powerpc code could be changed
to use the generic iommu code instead of using the powerpc specific code.


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