Re: [PATCH v2 cmpxchg 11/13] csky: Emulate one-byte cmpxchg

Guo Ren
2024-05-11T06:42:31Z

On Thu, May 2, 2024 at 7:01 AM Paul E. McKenney <paulmck@kernel.org> wrote:
>
> Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on csky.
>
> [ paulmck: Apply kernel test robot feedback. ]
> [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]
>
> Co-developed-by: Yujie Liu <yujie.liu@intel.com>
> Signed-off-by: Yujie Liu <yujie.liu@intel.com>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> Tested-by: Yujie Liu <yujie.liu@intel.com>
> Cc: Guo Ren <guoren@kernel.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: <linux-csky@vger.kernel.org>
> ---
> arch/csky/Kconfig | 1 +
> arch/csky/include/asm/cmpxchg.h | 10 ++++++++++
> 2 files changed, 11 insertions(+)
>
> diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
> index d3ac36751ad1f..5479707eb5d10 100644
> --- a/arch/csky/Kconfig
> +++ b/arch/csky/Kconfig
> @@ -37,6 +37,7 @@ config CSKY
> select ARCH_INLINE_SPIN_UNLOCK_BH if !PREEMPTION
> select ARCH_INLINE_SPIN_UNLOCK_IRQ if !PREEMPTION
> select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION
> + select ARCH_NEED_CMPXCHG_1_EMU
> select ARCH_WANT_FRAME_POINTERS if !CPU_CK610 && $(cc-option,-mbacktrace)
> select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
> select COMMON_CLK
> diff --git a/arch/csky/include/asm/cmpxchg.h b/arch/csky/include/asm/cmpxchg.h
> index 916043b845f14..db6dda47184e4 100644
> --- a/arch/csky/include/asm/cmpxchg.h
> +++ b/arch/csky/include/asm/cmpxchg.h
> @@ -6,6 +6,7 @@
> #ifdef CONFIG_SMP
> #include <linux/bug.h>
> #include <asm/barrier.h>
> +#include <linux/cmpxchg-emu.h>
>
> #define __xchg_relaxed(new, ptr, size) \
> ({ \
> @@ -61,6 +62,9 @@
> __typeof__(old) __old = (old); \
> __typeof__(*(ptr)) __ret; \
> switch (size) { \
> + case 1: \
> + __ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
> + break; \
> case 4: \
> asm volatile ( \
> "1: ldex.w %0, (%3) \n" \
> @@ -91,6 +95,9 @@
> __typeof__(old) __old = (old); \
> __typeof__(*(ptr)) __ret; \
> switch (size) { \
> + case 1: \
> + __ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
> + break; \
> case 4: \
> asm volatile ( \
> "1: ldex.w %0, (%3) \n" \
> @@ -122,6 +129,9 @@
> __typeof__(old) __old = (old); \
> __typeof__(*(ptr)) __ret; \
> switch (size) { \
> + case 1: \
> + __ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
> + break; \
> case 4: \
> asm volatile ( \
> RELEASE_FENCE \
> --
> 2.40.1
>
Reviewed-by: Guo Ren <guoren@kernel.org>

I will optimize it after ARCH_NEED_CMPXCHG_1_EMU is merged.

--
Best Regards
Guo Ren