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

[Mark Rutland]

On Sun, Jul 11, 2021 at 06:44:47AM +0800, kernel test robot wrote:
> Hi Mark,
> 
> FYI, the error/warning still remains.

I thought we'd already identified that this was an existing bug, and all that
has changed is the specific error that manifests.

In v5.13 this would fail with:

|   CC      drivers/iommu/io-pgtable-arm.o
| In file included from ./include/linux/atomic.h:84,
|                  from drivers/iommu/io-pgtable-arm.c:12:
| drivers/iommu/io-pgtable-arm.c: In function 'arm_lpae_install_table':
| ./include/linux/atomic-fallback.h:60:27: error: implicit declaration of function 'cmpxchg64'; did you mean 'cmpxchg'? [-Werror=implicit-function-declaration]
|    60 | #define cmpxchg64_relaxed cmpxchg64
|       |                           ^~~~~~~~~
| drivers/iommu/io-pgtable-arm.c:320:8: note: in expansion of macro 'cmpxchg64_relaxed'
|   320 |  old = cmpxchg64_relaxed(ptep, curr, new);
|       |        ^~~~~~~~~~~~~~~~~

... which has the same underlying problem -- the architecture has not provided
a cmpxchg64() implementation, but the IO pagetable code depends upon
cmpxchg64().

Thanks,
Mark.

> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   1e16624d7b4376797ede36e3c955375cf0f23298
> commit: bccf1ec369ac126b0997d01a6e1deae00e2cf6b3 locking/atomics: atomic-instrumented: simplify ifdeffery
> date:   6 weeks ago
> config: arc-allyesconfig (attached as .config)
> compiler: arceb-elf-gcc (GCC) 9.3.0
> 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=bccf1ec369ac126b0997d01a6e1deae00e2cf6b3
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout bccf1ec369ac126b0997d01a6e1deae00e2cf6b3
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arc 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> 
> 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-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);
>          |        ^~~~~~~~~~~~~~~~~
>    cc1: some warnings being treated as errors
> 
> 
> vim +60 include/linux/atomic-arch-fallback.h
> 
> 37f8173dd84936 Peter Zijlstra 2020-01-24  56  
> 37f8173dd84936 Peter Zijlstra 2020-01-24  57  #ifndef arch_cmpxchg64_relaxed
> 37f8173dd84936 Peter Zijlstra 2020-01-24  58  #define arch_cmpxchg64_acquire arch_cmpxchg64
> 37f8173dd84936 Peter Zijlstra 2020-01-24  59  #define arch_cmpxchg64_release arch_cmpxchg64
> 29f006fdefe6f8 Peter Zijlstra 2020-08-29 @60  #define arch_cmpxchg64_relaxed arch_cmpxchg64
> 37f8173dd84936 Peter Zijlstra 2020-01-24  61  #else /* arch_cmpxchg64_relaxed */
> 37f8173dd84936 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@xxxxxxxxxxxxx>
> :::::: CC: Ingo Molnar <mingo@xxxxxxxxxx>
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx