linux-kernel - Re: [PATCH cmpxchg 3/3] sh: Emulate one-byte cmpxchg

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Message-ID: <3f62ef41-aa71-4483-b0bd-cdd5e1caab38@paulmck-laptop>
Date: Mon, 5 Aug 2024 13:33:22 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	elver@...gle.com, akpm@...ux-foundation.org, tglx@...utronix.de,
	peterz@...radead.org, torvalds@...ux-foundation.org, arnd@...db.de,
	geert@...ux-m68k.org, palmer@...osinc.com, mhiramat@...nel.org,
	linux-sh@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
	Andi Shyti <andi.shyti@...ux.intel.com>
Subject: Re: [PATCH cmpxchg 3/3] sh: Emulate one-byte cmpxchg

On Mon, Aug 05, 2024 at 10:13:38PM +0200, John Paul Adrian Glaubitz wrote:
> On Mon, 2024-08-05 at 12:21 -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 1aa3c4a0c5b27..e9103998cca91 100644
> > --- a/arch/sh/Kconfig
> > +++ b/arch/sh/Kconfig
> > @@ -14,6 +14,7 @@ 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);
> >  	}
> 
> Acked-by: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>

Thank you very much!  I will apply this on my next rebase.

							Thanx, Paul