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

Paul E. McKenney
2024-05-11T14:49:57Z

On Sat, May 11, 2024 at 02:42:17PM +0800, Guo Ren wrote:
> 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.

Thank you very much! I have applied this and added it to my pull
request for the upcoming merge window.

Thanx, Paul