On Mon, 2011-05-16 at 15:26 -0500, Christoph Lameter wrote:
> plain text document attachment (cmpxchg_double_x86)
> A simple implementation that only supports the word size and does not
> have a fallback mode (would require a spinlock).
>
> And 32 and 64 bit support for cmpxchg_double. cmpxchg double uses
> the cmpxchg8b or cmpxchg16b instruction on x86 processors to compare
> and swap 2 machine words. This allows lockless algorithms to move more
> context information through critical sections.
>
> Set a flag CONFIG_CMPXCHG_DOUBLE to signal the support of that feature
> during kernel builds.
>
> Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
You forgot to CC Tejun for this patch.
> ---
> arch/x86/Kconfig.cpu | 3 ++
> arch/x86/include/asm/cmpxchg_32.h | 46 ++++++++++++++++++++++++++++++++++++++
> arch/x86/include/asm/cmpxchg_64.h | 45 +++++++++++++++++++++++++++++++++++++
> arch/x86/include/asm/cpufeature.h | 1
> 4 files changed, 95 insertions(+)
>
> Index: linux-2.6/arch/x86/include/asm/cmpxchg_64.h
> ===================================================================
> --- linux-2.6.orig/arch/x86/include/asm/cmpxchg_64.h 2011-05-16 11:40:36.421463498 -0500
> +++ linux-2.6/arch/x86/include/asm/cmpxchg_64.h 2011-05-16 11:46:34.781463079 -0500
> @@ -151,4 +151,49 @@ extern void __cmpxchg_wrong_size(void);
> cmpxchg_local((ptr), (o), (n)); \
> })
>
> +#define cmpxchg16b(ptr, o1, o2, n1, n2) \
> +({ \
> + char __ret; \
> + __typeof__(o2) __junk; \
> + __typeof__(*(ptr)) __old1 = (o1); \
> + __typeof__(o2) __old2 = (o2); \
> + __typeof__(*(ptr)) __new1 = (n1); \
> + __typeof__(o2) __new2 = (n2); \
> + asm volatile(LOCK_PREFIX_HERE "lock; cmpxchg16b (%%rsi);setz %1" \
> + : "=d"(__junk), "=a"(__ret) \
> + : "S"(ptr), "b"(__new1), "c"(__new2), \
> + "a"(__old1), "d"(__old2)); \
> + __ret; })
> +
> +
> +#define cmpxchg16b_local(ptr, o1, o2, n1, n2) \
> +({ \
> + char __ret; \
> + __typeof__(o2) __junk; \
> + __typeof__(*(ptr)) __old1 = (o1); \
> + __typeof__(o2) __old2 = (o2); \
> + __typeof__(*(ptr)) __new1 = (n1); \
> + __typeof__(o2) __new2 = (n2); \
> + asm volatile("cmpxchg16b (%%rsi)\n\t\tsetz %1\n\t" \
> + : "=d"(__junk)_, "=a"(__ret) \
> + : "S"((ptr)), "b"(__new1), "c"(__new2), \
> + "a"(__old1), "d"(__old2)); \
> + __ret; })
> +
> +#define cmpxchg_double(ptr, o1, o2, n1, n2) \
> +({ \
> + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
> + VM_BUG_ON((unsigned long)(ptr) % 16); \
> + cmpxchg16b((ptr), (o1), (o2), (n1), (n2)); \
> +})
> +
> +#define cmpxchg_double_local(ptr, o1, o2, n1, n2) \
> +({ \
> + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
> + VM_BUG_ON((unsigned long)(ptr) % 16); \
> + cmpxchg16b_local((ptr), (o1), (o2), (n1), (n2)); \
> +})
> +
> +#define system_has_cmpxchg_double() cpu_has_cx16
> +
> #endif /* _ASM_X86_CMPXCHG_64_H */
> Index: linux-2.6/arch/x86/include/asm/cmpxchg_32.h
> ===================================================================
> --- linux-2.6.orig/arch/x86/include/asm/cmpxchg_32.h 2011-05-16 11:40:36.431463498 -0500
> +++ linux-2.6/arch/x86/include/asm/cmpxchg_32.h 2011-05-16 11:46:34.781463079 -0500
> @@ -280,4 +280,50 @@ static inline unsigned long cmpxchg_386(
>
> #endif
>
> +#define cmpxchg8b(ptr, o1, o2, n1, n2) \
> +({ \
> + char __ret; \
> + __typeof__(o2) __dummy; \
> + __typeof__(*(ptr)) __old1 = (o1); \
> + __typeof__(o2) __old2 = (o2); \
> + __typeof__(*(ptr)) __new1 = (n1); \
> + __typeof__(o2) __new2 = (n2); \
> + asm volatile(LOCK_PREFIX_HERE "lock; cmpxchg8b (%%esi); setz %1"\
> + : "d="(__dummy), "=a" (__ret) \
> + : "S" ((ptr)), "a" (__old1), "d"(__old2), \
> + "b" (__new1), "c" (__new2) \
> + : "memory"); \
> + __ret; })
> +
> +
> +#define cmpxchg8b_local(ptr, o1, o2, n1, n2) \
> +({ \
> + char __ret; \
> + __typeof__(o2) __dummy; \
> + __typeof__(*(ptr)) __old1 = (o1); \
> + __typeof__(o2) __old2 = (o2); \
> + __typeof__(*(ptr)) __new1 = (n1); \
> + __typeof__(o2) __new2 = (n2); \
> + asm volatile("cmpxchg8b (%%esi); tsetz %1" \
> + : "d="(__dummy), "=a"(__ret) \
> + : "S" ((ptr)), "a" (__old), "d"(__old2), \
> + "b" (__new1), "c" (__new2), \
> + : "memory"); \
> + __ret; })
> +
> +
> +#define cmpxchg_double(ptr, o1, o2, n1, n2) \
> +({ \
> + BUILD_BUG_ON(sizeof(*(ptr)) != 4); \
> + VM_BUG_ON((unsigned long)(ptr) % 8); \
> + cmpxchg8b((ptr), (o1), (o2), (n1), (n2)); \
> +})
> +
> +#define cmpxchg_double_local(ptr, o1, o2, n1, n2) \
> +({ \
> + BUILD_BUG_ON(sizeof(*(ptr)) != 4); \
> + VM_BUG_ON((unsigned long)(ptr) % 8); \
> + cmpxchg16b_local((ptr), (o1), (o2), (n1), (n2)); \
> +})
> +
> #endif /* _ASM_X86_CMPXCHG_32_H */
> Index: linux-2.6/arch/x86/Kconfig.cpu
> ===================================================================
> --- linux-2.6.orig/arch/x86/Kconfig.cpu 2011-05-16 11:40:36.401463498 -0500
> +++ linux-2.6/arch/x86/Kconfig.cpu 2011-05-16 11:46:34.781463079 -0500
> @@ -308,6 +308,9 @@ config X86_CMPXCHG
> config CMPXCHG_LOCAL
> def_bool X86_64 || (X86_32 && !M386)
>
> +config CMPXCHG_DOUBLE
> + def_bool X86_64 || (X86_32 && !M386)
> +
> config X86_L1_CACHE_SHIFT
> int
> default "7" if MPENTIUM4 || MPSC
> Index: linux-2.6/arch/x86/include/asm/cpufeature.h
> ===================================================================
> --- linux-2.6.orig/arch/x86/include/asm/cpufeature.h 2011-05-16 11:40:36.411463498 -0500
> +++ linux-2.6/arch/x86/include/asm/cpufeature.h 2011-05-16 11:46:34.801463079 -0500
> @@ -286,6 +286,7 @@ extern const char * const x86_power_flag
> #define cpu_has_hypervisor boot_cpu_has(X86_FEATURE_HYPERVISOR)
> #define cpu_has_pclmulqdq boot_cpu_has(X86_FEATURE_PCLMULQDQ)
> #define cpu_has_perfctr_core boot_cpu_has(X86_FEATURE_PERFCTR_CORE)
> +#define cpu_has_cx16 boot_cpu_has(X86_FEATURE_CX16)
>
> #if defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_64)
> # define cpu_has_invlpg 1
>
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