Re: [PATCH v1] locking/atomic: xtensa: define arch_cmpxchg_local as __cmpxchg_local

[wuqiang.matt]

On 2023/11/4 17:31, Max Filippov wrote:
> On Sat, Nov 4, 2023 at 2:06 AM wuqiang.matt <wuqiang.matt@xxxxxxxxxxxxx> wrote:
> > The xtensa architecture already has __cmpxchg_local defined upon the
> > native __cmpxchg_u32 and __generic_cmpxchg_local
>
> This description does not make clear why this change is needed. Could you
> please expand it to cover the 'why' part?

The purpose of __cmpxchg_local() should be for arch_cmpxchg_local(), similarly
for other architectures like x86/arm/powerpc.

I noticed that arc/hexagon/openrisc/sh don't have arch_cmpxchg_local defined
because my patch triggered an error in kernel building. Then found xtensa's
definition of arch_cmpxchg_local() is not reasonable, so proposed this patch
to improve.

This change is not a must, but an improvement to simply make the codes of
arch_cmpxchg_local() more reasonable.

The patch link that introduced try_cmpxchg_local and triggered building error:
https://lore.kernel.org/all/20231023112452.6290-1-wuqiang.matt@xxxxxxxxxxxxx/

> > Signed-off-by: wuqiang.matt <wuqiang.matt@xxxxxxxxxxxxx>
> > ---
> >   arch/xtensa/include/asm/cmpxchg.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/xtensa/include/asm/cmpxchg.h b/arch/xtensa/include/asm/cmpxchg.h
> > index 675a11ea8de7..956c9925df1c 100644
> > --- a/arch/xtensa/include/asm/cmpxchg.h
> > +++ b/arch/xtensa/include/asm/cmpxchg.h
> > @@ -108,7 +108,7 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr,
> >    * them available.
> >    */
> >   #define arch_cmpxchg_local(ptr, o, n)                                         \
> > -       ((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), (unsigned long)(o),\
> > +       ((__typeof__(*(ptr)))__cmpxchg_local((ptr), (unsigned long)(o),        \
> >                          (unsigned long)(n), sizeof(*(ptr))))
> >   #define arch_cmpxchg64_local(ptr, o, n) __generic_cmpxchg64_local((ptr), (o), (n))
> >   #define arch_cmpxchg64(ptr, o, n)    arch_cmpxchg64_local((ptr), (o), (n))
> > --
> > 2.40.1