Re: [PATCH v3 cmpxchg 2/4] sh: Emulate one-byte cmpxchg

Hello,

On Tue, 2024-06-04 at 10:04 -0700, Paul E. McKenney wrote:
> Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on sh.
> 
> [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]
> [ paulmck: Apply feedback from Naresh Kamboju. ]
> [ Apply Geert Uytterhoeven feedback. ]
> 
> Signed-off-by: Paul E. McKenney <[email protected]>
> Cc: Andi Shyti <[email protected]>
> Cc: Palmer Dabbelt <[email protected]>
> Cc: Masami Hiramatsu <[email protected]>
> Cc: Arnd Bergmann <[email protected]>
> Cc: <[email protected]>
> ---
>  arch/sh/Kconfig               | 1 +
>  arch/sh/include/asm/cmpxchg.h | 3 +++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
> index 5e6a3ead51fb1..f723e2256c9c1 100644
> --- a/arch/sh/Kconfig
> +++ b/arch/sh/Kconfig
> @@ -16,6 +16,7 @@ config SUPERH
>  	select ARCH_HIBERNATION_POSSIBLE if MMU
>  	select ARCH_MIGHT_HAVE_PC_PARPORT
>  	select ARCH_WANT_IPC_PARSE_VERSION
> +	select ARCH_NEED_CMPXCHG_1_EMU
>  	select CPU_NO_EFFICIENT_FFS
>  	select DMA_DECLARE_COHERENT
>  	select GENERIC_ATOMIC64
> diff --git a/arch/sh/include/asm/cmpxchg.h b/arch/sh/include/asm/cmpxchg.h
> index 5d617b3ef78f7..1e5dc5ccf7bf5 100644
> --- a/arch/sh/include/asm/cmpxchg.h
> +++ b/arch/sh/include/asm/cmpxchg.h
> @@ -9,6 +9,7 @@
>  
>  #include <linux/compiler.h>
>  #include <linux/types.h>
> +#include <linux/cmpxchg-emu.h>
>  
>  #if defined(CONFIG_GUSA_RB)
>  #include <asm/cmpxchg-grb.h>
> @@ -56,6 +57,8 @@ static inline unsigned long __cmpxchg(volatile void * ptr, unsigned long old,
>  		unsigned long new, int size)
>  {
>  	switch (size) {
> +	case 1:
> +		return cmpxchg_emu_u8(ptr, old, new);
>  	case 4:
>  		return __cmpxchg_u32(ptr, old, new);
>  	}

Reviewed-by: John Paul Adrian Glaubitz <[email protected]>

I can pick this up through my SH tree unless someone insists this to
go through some other tree.

Adrian

PS: I'm a bit stumped that I'm not CC'ed as the SH maintainer.

-- 
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: :' :  Debian Developer
`. `'   Physicist
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