linux-kernel - Re: [PATCH v4 next 6/9] lib: test_mul_u64_u64_div

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Message-ID: <20251102103600.65754bf2@pumpkin>
Date: Sun, 2 Nov 2025 10:36:00 +0000
From: David Laight <david.laight.linux@...il.com>
To: kernel test robot <lkp@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
 llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev, Linux Memory
 Management List <linux-mm@...ck.org>, u.kleine-koenig@...libre.com, Nicolas
 Pitre <npitre@...libre.com>, Oleg Nesterov <oleg@...hat.com>, Peter
 Zijlstra <peterz@...radead.org>, Biju Das <biju.das.jz@...renesas.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Thomas
 Gleixner <tglx@...utronix.de>, Li RongQing <lirongqing@...du.com>, Yu Kuai
 <yukuai3@...wei.com>, Khazhismel Kumykov <khazhy@...omium.org>, Jens Axboe
 <axboe@...nel.dk>, x86@...nel.org
Subject: Re: [PATCH v4 next 6/9] lib: test_mul_u64_u64_div_u64: Test both
 generic and arch versions

On Sun, 2 Nov 2025 04:59:10 +0800
kernel test robot <lkp@...el.com> wrote:

> Hi David,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on next-20251029]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/David-Laight/lib-mul_u64_u64_div_u64-rename-parameter-c-to-d/20251030-025633
> base:   next-20251029
> patch link:    https://lore.kernel.org/r/20251029173828.3682-7-david.laight.linux%40gmail.com
> patch subject: [PATCH v4 next 6/9] lib: test_mul_u64_u64_div_u64: Test both generic and arch versions
> config: i386-buildonly-randconfig-004-20251102 (https://download.01.org/0day-ci/archive/20251102/202511020421.ZZPBAIIw-lkp@intel.com/config)
> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251102/202511020421.ZZPBAIIw-lkp@intel.com/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@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202511020421.ZZPBAIIw-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
> >> lib/math/test_mul_u64_u64_div_u64.c:142:9: warning: '__div64_32' macro redefined [-Wmacro-redefined]  
>      142 | #define __div64_32 __div64_32
>          |         ^
>    arch/x86/include/asm/div64.h:78:9: note: previous definition is here
>       78 | #define __div64_32

That is preceded by a comment that says it can't happen for x86-64.
I think it would be better as '#define __div64_32 @@@' so that you get a compile
error.
But that isn't part of this change,
>          |         ^
>    1 warning generated.
> 
> 
> vim +/__div64_32 +142 lib/math/test_mul_u64_u64_div_u64.c
> 
>    140	
>    141	/* Compile the generic mul_u64_add_u64_div_u64() code */
>  > 142	#define __div64_32 __div64_32  

It needs a preceding #undef
Although I'm not sure why a normal build doesn't show it.

Looks like I'll need to do a v5 :-(

	David

>    143	#define div_s64_rem div_s64_rem
>    144	#define div64_u64_rem div64_u64_rem
>    145	#define div64_u64 div64_u64
>    146	#define div64_s64 div64_s64
>    147	#define iter_div_u64_rem iter_div_u64_rem
>    148	
>