From: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
To: "Paul E. McKenney" <paulmck@kernel.org>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: elver@google.com, akpm@linux-foundation.org, tglx@linutronix.de,
peterz@infradead.org, dianders@chromium.org, pmladek@suse.com,
arnd@arndb.de, torvalds@linux-foundation.org,
kernel-team@meta.com, Andi Shyti <andi.shyti@linux.intel.com>,
Palmer Dabbelt <palmer@rivosinc.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
linux-sh@vger.kernel.org
Subject: Re: [PATCH v2 cmpxchg 12/13] sh: Emulate one-byte cmpxchg
Date: Thu, 02 May 2024 06:52:53 +0200 [thread overview]
Message-ID: <1376850f47279e3a3f4f40e3de2784ae3ac30414.camel@physik.fu-berlin.de> (raw)
In-Reply-To: <20240501230130.1111603-12-paulmck@kernel.org>
Hi Paul,
On Wed, 2024-05-01 at 16:01 -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@kernel.org>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Cc: Palmer Dabbelt <palmer@rivosinc.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: <linux-sh@vger.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 2ad3e29f0ebec..f47e9ccf4efd2 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);
> }
Thanks for the patch. However, I don't quite understand its purpose.
There is already a case for 8-byte cmpxchg in the switch statement below:
case 1: \
__xchg__res = xchg_u8(__xchg_ptr, x); \
break;
Does cmpxchg_emu_u8() have any advantages over the native xchg_u8()?
Thanks,
Adrian
--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer
`. `' Physicist
`- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
next prev parent reply other threads:[~2024-05-02 4:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <b67e79d4-06cb-4a45-a906-b9e0fbae22c5@paulmck-laptop>
2024-05-01 23:01 ` [PATCH v2 cmpxchg 12/13] sh: Emulate one-byte cmpxchg Paul E. McKenney
2024-05-02 4:52 ` John Paul Adrian Glaubitz [this message]
2024-05-02 5:06 ` Paul E. McKenney
2024-05-02 5:11 ` John Paul Adrian Glaubitz
2024-05-02 13:33 ` Paul E. McKenney
2024-05-02 20:53 ` Al Viro
2024-05-02 21:01 ` alpha cmpxchg.h (was Re: [PATCH v2 cmpxchg 12/13] sh: Emulate one-byte cmpxchg) Al Viro
2024-05-02 22:16 ` Linus Torvalds
2024-05-02 21:18 ` [PATCH v2 cmpxchg 12/13] sh: Emulate one-byte cmpxchg Paul E. McKenney
2024-05-02 22:07 ` Al Viro
2024-05-02 23:12 ` Paul E. McKenney
2024-05-02 23:24 ` Al Viro
2024-05-02 23:45 ` Paul E. McKenney
2024-05-02 23:32 ` Linus Torvalds
2024-05-03 0:16 ` Paul E. McKenney
2024-05-02 21:50 ` Arnd Bergmann
2024-05-02 5:42 ` D. Jeff Dionne
2024-05-02 11:30 ` Arnd Bergmann
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