Re: [paulmck-rcu:dev.2024.03.27b 64/69] arch/xtensa/include/asm/cmpxchg.h:77:25: error: implicit declaration of function 'cmpxchg_emu_u8'

[Paul E. McKenney]

On Fri, Mar 29, 2024 at 11:08:04PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2024.03.27b
> head:   786fab3085d764055a78edb54023420920344333
> commit: b3b1a154281fc97efc4c1d5818a83c29c228dbd5 [64/69] xtensa: Emulate one-byte and two-byte cmpxchg
> config: xtensa-allnoconfig (https://download.01.org/0day-ci/archive/20240329/202403292321.T55etywH-lkp@xxxxxxxxx/config)
> compiler: xtensa-linux-gcc (GCC) 13.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240329/202403292321.T55etywH-lkp@xxxxxxxxx/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202403292321.T55etywH-lkp@xxxxxxxxx/
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from arch/xtensa/include/asm/atomic.h:19,
>                     from include/linux/atomic.h:7,
>                     from include/asm-generic/bitops/atomic.h:5,
>                     from arch/xtensa/include/asm/bitops.h:192,
>                     from include/linux/bitops.h:68,
>                     from include/linux/log2.h:12,
>                     from kernel/bounds.c:13:
>    arch/xtensa/include/asm/cmpxchg.h: In function '__cmpxchg':
> >> arch/xtensa/include/asm/cmpxchg.h:77:25: error: implicit declaration of function 'cmpxchg_emu_u8' [-Werror=implicit-function-declaration]
>       77 |         case 1:  return cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
>          |                         ^~~~~~~~~~~~~~

Good catch!  Does the diff at the end fix this?

							Thanx, Paul

> >> arch/xtensa/include/asm/cmpxchg.h:78:25: error: implicit declaration of function 'cmpxchg_emu_u16' [-Werror=implicit-function-declaration]
>       78 |         case 2:  return cmpxchg_emu_u16((volatile u16 *)ptr, old, new);
>          |                         ^~~~~~~~~~~~~~~
>    cc1: some warnings being treated as errors
>    make[3]: *** [scripts/Makefile.build:117: kernel/bounds.s] Error 1
>    make[3]: Target 'prepare' not remade because of errors.
>    make[2]: *** [Makefile:1197: prepare0] Error 2
>    make[2]: Target 'prepare' not remade because of errors.
>    make[1]: *** [Makefile:240: __sub-make] Error 2
>    make[1]: Target 'prepare' not remade because of errors.
>    make: *** [Makefile:240: __sub-make] Error 2
>    make: Target 'prepare' not remade because of errors.
> 
> 
> vim +/cmpxchg_emu_u8 +77 arch/xtensa/include/asm/cmpxchg.h
> 
>     72	
>     73	static __inline__ unsigned long
>     74	__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
>     75	{
>     76		switch (size) {
>   > 77		case 1:  return cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
>   > 78		case 2:  return cmpxchg_emu_u16((volatile u16 *)ptr, old, new);
>     79		case 4:  return __cmpxchg_u32(ptr, old, new);
>     80		default: __cmpxchg_called_with_bad_pointer();
>     81			 return old;
>     82		}
>     83	}
>     84	
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

commit 663161aaa5c3286dcfc9ba2cd9e12170f9354ea7
Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
Date:   Fri Mar 29 11:47:13 2024 -0700

    squash! xtensa: Emulate one-byte and two-byte cmpxchg
    
    [ paulmck: Apply kernel test robot feedback. ]
    
    Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

diff --git a/arch/xtensa/include/asm/cmpxchg.h b/arch/xtensa/include/asm/cmpxchg.h
index bcce915a98e21..a0f9a2070209b 100644
--- a/arch/xtensa/include/asm/cmpxchg.h
+++ b/arch/xtensa/include/asm/cmpxchg.h
@@ -15,6 +15,7 @@
 
 #include <linux/bits.h>
 #include <linux/stringify.h>
+#include <linux/cmpxchg-emu.h>
 
 /*
  * cmpxchg