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

Andrew Morton
2020-11-09T02:55:26Z

On Mon, 9 Nov 2020 08:20:05 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:

>
>
> 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.
>
> https://lore.kernel.org/linux-arm-kernel/20201106085157.11211-1-linus.walleij@linaro.org/

Yes, but why? macros-pretending-to-be-functions just keep on causing
problems and they're so unnecessary. Why not just write functions in
the first place?? Did anyone try implementing that?