linux-kernel - Re: [PATCH v2 00/33] locking/atomic: convert all architectures to ARCH

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Message-ID: <a38e3284-62ee-4894-0475-2668733c5903@infradead.org>
Date:   Mon, 28 Jun 2021 15:21:06 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org,
        will@...nel.org, boqun.feng@...il.com, aou@...s.berkeley.edu,
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Subject: Re: [PATCH v2 00/33] locking/atomic: convert all architectures to
 ARCH_ATOMIC

On 6/28/21 3:13 PM, Peter Zijlstra wrote:
> On Mon, Jun 28, 2021 at 02:22:15PM -0700, Randy Dunlap wrote:
>> However, something in arch/arc/ did look suspicious so I decided to
>> try an ARC allmodconfig build, where I did see a few errors FYI:
>>
>>
>>   CC      drivers/iommu/io-pgtable-arm.o
>> In file included from ../include/linux/atomic.h:80,
>>                  from ../drivers/iommu/io-pgtable-arm.c:12:
>> ../drivers/iommu/io-pgtable-arm.c: In function 'arm_lpae_install_table':
>> ../include/linux/atomic-arch-fallback.h:60:32: error: implicit declaration of function 'arch_cmpxchg64'; did you mean 'arch_cmpxchg'? [-Werror=implicit-function-declaration]
>>    60 | #define arch_cmpxchg64_relaxed arch_cmpxchg64
>>       |                                ^~~~~~~~~~~~~~
>> ../include/asm-generic/atomic-instrumented.h:1261:2: note: in expansion of macro 'arch_cmpxchg64_relaxed'
>>  1261 |  arch_cmpxchg64_relaxed(__ai_ptr, __VA_ARGS__); \
>>       |  ^~~~~~~~~~~~~~~~~~~~~~
>> ../drivers/iommu/io-pgtable-arm.c:320:8: note: in expansion of macro 'cmpxchg64_relaxed'
>>   320 |  old = cmpxchg64_relaxed(ptep, curr, new);
>>       |        ^~~~~~~~~~~~~~~~~
> 
> 0day also reported something like that. We found that this was a
> pre-existing error, and Mark's patches only changed the error, it never
> successfully build.
> 
> cmpxchg64 is an optional feature for 32bit architectures, one that ARMv7
> does provide, and uses, for it's iommu bits. Building the ARM iommu
> drivers on ARC seem somewhat daft but is a result of that COMPILE_TEST
> config.
> 

Yes, I realize it's just a COMPILE_TEST config. Not very interesting IMHO.

Thanks.