Hi Huacai,
On Sat, Jul 24, 2021 at 2:36 PM Huacai Chen <chenhuacai@xxxxxxxxxxx> wrote:
> Introduce a new Kconfig option ARCH_HAS_HW_XCHG_SMALL, which means arch
> has hardware sub-word xchg/cmpxchg support. This option will be used as
> an indicator to select the bit-field definition in the qspinlock data
> structure.
>
> Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Thanks for your patch!
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -228,6 +228,10 @@ config ARCH_HAS_FORTIFY_SOURCE
> An architecture should select this when it can successfully
> build and run with CONFIG_FORTIFY_SOURCE.
>
> +# Select if arch has hardware sub-word xchg/cmpxchg support
> +config ARCH_HAS_HW_XCHG_SMALL
What do you mean by "hardware"?
Does a software fallback count?
> --- a/arch/m68k/Kconfig
> +++ b/arch/m68k/Kconfig
> @@ -5,6 +5,7 @@ config M68K
> select ARCH_32BIT_OFF_T
> select ARCH_HAS_BINFMT_FLAT
> select ARCH_HAS_DMA_PREP_COHERENT if HAS_DMA && MMU && !COLDFIRE
> + select ARCH_HAS_HW_XCHG_SMALL
M68k CPUs which support the CAS (Compare And Set) instruction do
support this on 8-bit, 16-bit, and 32-bit quantities.
M68k CPUs which lack CAS use a software implementation, which
supports the same quantities.
As CAS is used only if CONFIG_RMW_INSNS=y, perhaps this needs
a dependency?
select ARCH_HAS_HW_XCHG_SMALL if RMW_INSNS
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
