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

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Date: Tue, 04 Jun 2024 19:09:11 +0200
From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To: "Paul E. McKenney" <paulmck@...nel.org>, linux-arch@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com, elver@...gle.com, 
	akpm@...ux-foundation.org, tglx@...utronix.de, peterz@...radead.org, 
	dianders@...omium.org, pmladek@...e.com, torvalds@...ux-foundation.org, 
	arnd@...db.de, Andi Shyti <andi.shyti@...ux.intel.com>, Palmer Dabbelt
	 <palmer@...osinc.com>, Masami Hiramatsu <mhiramat@...nel.org>, 
	linux-sh@...r.kernel.org
Subject: 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 <paulmck@...nel.org>
> Cc: Andi Shyti <andi.shyti@...ux.intel.com>
> Cc: Palmer Dabbelt <palmer@...osinc.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: <linux-sh@...r.kernel.org>
> ---
>  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 <glaubitz@...sik.fu-berlin.de>

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.

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
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