Re: [PATCH] selftests/mm: reuse FORCE_READ to replace "asm volatile("" : "+r" (XXX));"

[Wei Yang <richard.weiyang@gmail.com>]

On Wed, Jul 16, 2025 at 03:15:43PM -0700, Andrew Morton wrote:
>On Wed, 16 Jul 2025 20:31:26 +0800 wang lian <lianux.mm@gmail.com> wrote:
>
>> Several mm selftests use the `asm volatile("" : "+r" (variable));`
>> construct to force a read of a variable, preventing the compiler from
>> optimizing away the memory access. This idiom is cryptic and duplicated
>> across multiple test files.
>> 
>> Following a suggestion from David[1], this patch refactors this
>> common pattern into a FORCE_READ() macro
>> 
>>  tools/testing/selftests/mm/cow.c              | 30 +++++++++----------
>>  tools/testing/selftests/mm/hugetlb-madvise.c  |  5 +---
>>  tools/testing/selftests/mm/migration.c        | 13 ++++----
>>  tools/testing/selftests/mm/pagemap_ioctl.c    |  4 +--
>>  .../selftests/mm/split_huge_page_test.c       |  4 +--
>>  5 files changed, 24 insertions(+), 32 deletions(-)
>
>The patch forgot to move the FORCE_READ definition into a header?
>

I get this after applying the patch.

cow.c:1559:9: warning: implicit declaration of function ‘FORCE_READ’; did you mean ‘LOCK_READ’? [-Wimplicit-function-declaration]
 1559 |         FORCE_READ(mem);

-- 
Wei Yang
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