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

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Date: Tue, 4 Jun 2024 10:50:36 -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,
	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

On Tue, Jun 04, 2024 at 07:09:11PM +0200, John Paul Adrian Glaubitz wrote:
> 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.

Please do take it, and thank you!  When I see it in -next, I will drop
it from my tree.

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

Me too, now that you mention it.  I did generate the list some time
back, but "git blame" shows you being maintainer for more than a year.
Yet I do have the linux-sh email list, so it is unlikely that I pasted
the get_maintainer.pl output from the wrong commit.

I am forced to hypothesize that I fat-fingered the output of
get_maintainer.pl when adding the Cc lines to that commit.

Please accept my apologies for having left you out!

							Thanx, Paul