Re: [linux-next:master] BUILD REGRESSION 0a6f624a86e766a27d23cbb73c23be62231d10ff

Anshuman Khandual
2020-11-09T02:50:14Z

On 11/7/20 10:37 AM, Andrew Morton wrote:
> On Fri, 06 Nov 2020 08:19:36 +0800 kernel test robot <lkp@intel.com> wrote:
>
>> tree/branch: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>> branch HEAD: 0a6f624a86e766a27d23cbb73c23be62231d10ff Add linux-next specific files for 20201105
>>
>> Error/Warning reports:
>>
>> https://lore.kernel.org/linux-mm/202010281624.9m2gZw45-lkp@intel.com
>> https://lore.kernel.org/linux-mm/202010290238.M1tDrV8p-lkp@intel.com
>> https://lore.kernel.org/linux-mm/202010291054.WEZO3olr-lkp@intel.com
>> https://lore.kernel.org/linux-mm/202011020749.5XQ3Hfzc-lkp@intel.com
>>
>> ...
>>
>> mm/kasan/init.c:318:9: warning: variable 'pud' set but not used [-Wunused-but-set-variable]
>>
>
> This is because mm/kasan/init.c does
>
> static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
> {
> pud_t *pud;
> int i;
>
> for (i = 0; i < PTRS_PER_PUD; i++) {
> pud = pud_start + i;
> if (!pud_none(*pud))
> return;
> }
>
> pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
> p4d_clear(p4d);
> }
>
> but arch/arm/include/asm/pgtable-2level.h does
>
> #define pud_none(pud) (0)
>
> The solution here is for the arm implementation to reference `pud'.
> Typically this is done via the use of an empty static inline C function
> rather than a macro. But really all of these
>
> #define pud_none(pud) (0)
> #define pud_bad(pud) (0)
> #define pud_present(pud) (1)
> #define pud_clear(pudp) do { } while (0)
> #define set_pud(pud,pudp) do { } while (0)
>
> should be thus converted.
>
> Could someone in arm world please attend to this?

+ Ard Biesheuvel <ardb@kernel.org>
+ Linus Walleij <linus.walleij@linaro.org>

There were some earlier discussions to solve this in a different way.

https://lore.kernel.org/linux-mm/CACRpkdbAXCMTW--BmVs8SQ_u5baaeUob+U57E=4=CrMxWtMO2g@mail.gmail.com/

with a subsequent follow up patch.