Re: include/linux/atomic/atomic-arch-fallback.h:60:32: error: implicit declaration of function 'arch_cmpxchg64'; did you mean 'arch_cmpxchg'?

[Mark Rutland <mark.rutland@arm.com>]

On Sun, Sep 12, 2021 at 04:24:21AM +0800, kernel test robot wrote:
> Hi Mark,
> 
> FYI, the error/warning still remains.

As pointed out previously [1,2], this is an existing bug (in that arc
does not have an implementation of cmpxchg64(), but it's possible to
select code which uses it in test configurations). My changes to the
core atomic headers only change the way in which the error manifests,
and have nothing to do with the underlying problem.

I thought we were going to stop reporting this [3]?

If we want to "fix" this kernel side, then we either need to:

* Implement cmpxchg64() for arc

* Add an ARCH_HAS_CMPXCHG64, and dependencies in kconfig where it is used

Thanks,
Mark.

[1] https://lore.kernel.org/lkml/a38e3284-62ee-4894-0475-2668733c5903@infradead.org/
[2] https://lore.kernel.org/lkml/20210712143151.GB94622@C02TD0UTHF1T.local/
[3] https://lore.kernel.org/lkml/717d9f89-078b-1698-46fb-9b3393ecddc4@intel.com/

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   c605c39677b9842b0566013e0cf30bc13e90bdbc
> commit: e3d18cee258b898017b298b5b93f8134dd62aee3 locking/atomic: centralize generated headers
> date:   8 weeks ago
> config: arc-allyesconfig (attached as .config)
> compiler: arceb-elf-gcc (GCC) 11.2.0
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e3d18cee258b898017b298b5b93f8134dd62aee3
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout e3d18cee258b898017b298b5b93f8134dd62aee3
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=arc 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
> 
>    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/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/linux/atomic/atomic-instrumented.h:1261:9: note: in expansion of macro 'arch_cmpxchg64_relaxed'
>     1261 |         arch_cmpxchg64_relaxed(__ai_ptr, __VA_ARGS__); \
>          |         ^~~~~~~~~~~~~~~~~~~~~~
>    drivers/iommu/io-pgtable-arm.c:320:15: note: in expansion of macro 'cmpxchg64_relaxed'
>      320 |         old = cmpxchg64_relaxed(ptep, curr, new);
>          |               ^~~~~~~~~~~~~~~~~
>    cc1: some warnings being treated as errors
> 
> 
> vim +60 include/linux/atomic/atomic-arch-fallback.h
> 
> 37f8173dd84936 include/linux/atomic-arch-fallback.h Peter Zijlstra 2020-01-24  56  
> 37f8173dd84936 include/linux/atomic-arch-fallback.h Peter Zijlstra 2020-01-24  57  #ifndef arch_cmpxchg64_relaxed
> 37f8173dd84936 include/linux/atomic-arch-fallback.h Peter Zijlstra 2020-01-24  58  #define arch_cmpxchg64_acquire arch_cmpxchg64
> 37f8173dd84936 include/linux/atomic-arch-fallback.h Peter Zijlstra 2020-01-24  59  #define arch_cmpxchg64_release arch_cmpxchg64
> 29f006fdefe6f8 include/linux/atomic-arch-fallback.h Peter Zijlstra 2020-08-29 @60  #define arch_cmpxchg64_relaxed arch_cmpxchg64
> 37f8173dd84936 include/linux/atomic-arch-fallback.h Peter Zijlstra 2020-01-24  61  #else /* arch_cmpxchg64_relaxed */
> 37f8173dd84936 include/linux/atomic-arch-fallback.h Peter Zijlstra 2020-01-24  62  
> 
> :::::: The code at line 60 was first introduced by commit
> :::::: 29f006fdefe6f88abde973a0b0f20d2704e93fd4 asm-generic/atomic: Add try_cmpxchg() fallbacks
> 
> :::::: TO: Peter Zijlstra <peterz@infradead.org>
> :::::: CC: Ingo Molnar <mingo@kernel.org>
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org