From 7296e08abac0a22a2534a4f6e493c764f2c77583 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Tue, 14 Dec 2010 10:28:44 -0600 Subject: [PATCH] x86: this_cpu_cmpxchg and this_cpu_xchg operations Provide support as far as the hardware capabilities of the x86 cpus allow. Define CONFIG_CMPXCHG_LOCAL in Kconfig.cpu to allow core code to test for fast cpuops implementations. V1->V2: - Take out the definition for this_cpu_cmpxchg_8 and move it into a separate patch. tj: - Reordered ops to better follow this_cpu_* organization. - Renamed macro temp variables similar to their existing neighbours. Signed-off-by: Christoph Lameter Signed-off-by: Tejun Heo --- arch/x86/Kconfig.cpu | 3 + arch/x86/include/asm/percpu.h | 107 +++++++++++++++++++++++++++++++++- 2 files changed, 109 insertions(+), 1 deletion(-) diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu index 2ac9069890cd..15588a0ef466 100644 --- a/arch/x86/Kconfig.cpu +++ b/arch/x86/Kconfig.cpu @@ -310,6 +310,9 @@ config X86_INTERNODE_CACHE_SHIFT config X86_CMPXCHG def_bool X86_64 || (X86_32 && !M386) +config CMPXCHG_LOCAL + def_bool X86_64 || (X86_32 && !M386) + config X86_L1_CACHE_SHIFT int default "7" if MPENTIUM4 || MPSC diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index dd0cd4b6a76f..b85ade511a53 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -262,6 +262,83 @@ do { \ paro_ret__; \ }) +/* + * Beware: xchg on x86 has an implied lock prefix. There will be the cost of + * full lock semantics even though they are not needed. + */ +#define percpu_xchg_op(var, nval) \ +({ \ + typeof(var) pxo_ret__; \ + typeof(var) pxo_new__ = (nval); \ + switch (sizeof(var)) { \ + case 1: \ + asm("xchgb %2, "__percpu_arg(1) \ + : "=a" (pxo_ret__), "+m" (var) \ + : "q" (pxo_new__) \ + : "memory"); \ + break; \ + case 2: \ + asm("xchgw %2, "__percpu_arg(1) \ + : "=a" (pxo_ret__), "+m" (var) \ + : "r" (pxo_new__) \ + : "memory"); \ + break; \ + case 4: \ + asm("xchgl %2, "__percpu_arg(1) \ + : "=a" (pxo_ret__), "+m" (var) \ + : "r" (pxo_new__) \ + : "memory"); \ + break; \ + case 8: \ + asm("xchgq %2, "__percpu_arg(1) \ + : "=a" (pxo_ret__), "+m" (var) \ + : "r" (pxo_new__) \ + : "memory"); \ + break; \ + default: __bad_percpu_size(); \ + } \ + pxo_ret__; \ +}) + +/* + * cmpxchg has no such implied lock semantics as a result it is much + * more efficient for cpu local operations. + */ +#define percpu_cmpxchg_op(var, oval, nval) \ +({ \ + typeof(var) pco_ret__; \ + typeof(var) pco_old__ = (oval); \ + typeof(var) pco_new__ = (nval); \ + switch (sizeof(var)) { \ + case 1: \ + asm("cmpxchgb %2, "__percpu_arg(1) \ + : "=a" (pco_ret__), "+m" (var) \ + : "q" (pco_new__), "0" (pco_old__) \ + : "memory"); \ + break; \ + case 2: \ + asm("cmpxchgw %2, "__percpu_arg(1) \ + : "=a" (pco_ret__), "+m" (var) \ + : "r" (pco_new__), "0" (pco_old__) \ + : "memory"); \ + break; \ + case 4: \ + asm("cmpxchgl %2, "__percpu_arg(1) \ + : "=a" (pco_ret__), "+m" (var) \ + : "r" (pco_new__), "0" (pco_old__) \ + : "memory"); \ + break; \ + case 8: \ + asm("cmpxchgq %2, "__percpu_arg(1) \ + : "=a" (pco_ret__), "+m" (var) \ + : "r" (pco_new__), "0" (pco_old__) \ + : "memory"); \ + break; \ + default: __bad_percpu_size(); \ + } \ + pco_ret__; \ +}) + /* * percpu_read() makes gcc load the percpu variable every time it is * accessed while percpu_read_stable() allows the value to be cached. @@ -300,6 +377,12 @@ do { \ #define __this_cpu_xor_1(pcp, val) percpu_to_op("xor", (pcp), val) #define __this_cpu_xor_2(pcp, val) percpu_to_op("xor", (pcp), val) #define __this_cpu_xor_4(pcp, val) percpu_to_op("xor", (pcp), val) +/* + * Generic fallback operations for __this_cpu_xchg_[1-4] are okay and much + * faster than an xchg with forced lock semantics. + */ +#define __this_cpu_xchg_8(pcp, nval) percpu_xchg_op(pcp, nval) +#define __this_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) #define this_cpu_read_1(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) #define this_cpu_read_2(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) @@ -319,6 +402,11 @@ do { \ #define this_cpu_xor_1(pcp, val) percpu_to_op("xor", (pcp), val) #define this_cpu_xor_2(pcp, val) percpu_to_op("xor", (pcp), val) #define this_cpu_xor_4(pcp, val) percpu_to_op("xor", (pcp), val) +#define this_cpu_xchg_1(pcp, nval) percpu_xchg_op(pcp, nval) +#define this_cpu_xchg_2(pcp, nval) percpu_xchg_op(pcp, nval) +#define this_cpu_xchg_4(pcp, nval) percpu_xchg_op(pcp, nval) +#define this_cpu_xchg_8(pcp, nval) percpu_xchg_op(pcp, nval) +#define this_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) #define irqsafe_cpu_add_1(pcp, val) percpu_add_op((pcp), val) #define irqsafe_cpu_add_2(pcp, val) percpu_add_op((pcp), val) @@ -332,15 +420,32 @@ do { \ #define irqsafe_cpu_xor_1(pcp, val) percpu_to_op("xor", (pcp), val) #define irqsafe_cpu_xor_2(pcp, val) percpu_to_op("xor", (pcp), val) #define irqsafe_cpu_xor_4(pcp, val) percpu_to_op("xor", (pcp), val) +#define irqsafe_cpu_xchg_1(pcp, nval) percpu_xchg_op(pcp, nval) +#define irqsafe_cpu_xchg_2(pcp, nval) percpu_xchg_op(pcp, nval) +#define irqsafe_cpu_xchg_4(pcp, nval) percpu_xchg_op(pcp, nval) +#define irqsafe_cpu_xchg_8(pcp, nval) percpu_xchg_op(pcp, nval) +#define irqsafe_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) #ifndef CONFIG_M386 #define __this_cpu_add_return_1(pcp, val) percpu_add_return_op(pcp, val) #define __this_cpu_add_return_2(pcp, val) percpu_add_return_op(pcp, val) #define __this_cpu_add_return_4(pcp, val) percpu_add_return_op(pcp, val) +#define __this_cpu_cmpxchg_1(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) +#define __this_cpu_cmpxchg_2(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) +#define __this_cpu_cmpxchg_4(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) + #define this_cpu_add_return_1(pcp, val) percpu_add_return_op(pcp, val) #define this_cpu_add_return_2(pcp, val) percpu_add_return_op(pcp, val) #define this_cpu_add_return_4(pcp, val) percpu_add_return_op(pcp, val) -#endif +#define this_cpu_cmpxchg_1(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) +#define this_cpu_cmpxchg_2(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) +#define this_cpu_cmpxchg_4(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) + +#define irqsafe_cpu_cmpxchg_1(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) +#define irqsafe_cpu_cmpxchg_2(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) +#define irqsafe_cpu_cmpxchg_4(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) +#endif /* !CONFIG_M386 */ + /* * Per cpu atomic 64 bit operations are only available under 64 bit. * 32 bit must fall back to generic operations. -- 2.34.1