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Subject[cpuops inc_return V1 2/9] x86: Support for this_cpu_add,sub,dec,inc_return
Supply an implementation for x86 in order to generate more efficient code.

V2->V3:
- Cleanup
- Remove strange type checking from percpu_add_return_op.

Signed-off-by: Christoph Lameter <cl@linux.com>

---
arch/x86/include/asm/percpu.h | 46 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)
Index: linux-2.6/arch/x86/include/asm/percpu.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/percpu.h 2010-11-29 14:29:13.000000000 -0600
+++ linux-2.6/arch/x86/include/asm/percpu.h 2010-11-30 08:42:02.000000000 -0600
@@ -177,6 +177,41 @@ do { \
} \
} while (0)

+
+/*
+ * Add return operation
+ */
+#define percpu_add_return_op(var, val) \
+({ \
+ typedef typeof(var) pao_T__; \
+ typeof(var) ret__ = val; \
+ switch (sizeof(var)) { \
+ case 1: \
+ asm("xaddb %0, "__percpu_arg(1) \
+ : "+q" (ret__), "+m" (var) \
+ : : "memory"); \
+ break; \
+ case 2: \
+ asm("xaddw %0, "__percpu_arg(1) \
+ : "+r" (ret__), "+m" (var) \
+ : : "memory"); \
+ break; \
+ case 4: \
+ asm("xaddl %0, "__percpu_arg(1) \
+ : "+r"(ret__), "+m" (var) \
+ : : "memory"); \
+ break; \
+ case 8: \
+ asm("xaddq %0, "__percpu_arg(1) \
+ : "+re" (ret__), "+m" (var) \
+ : : "memory"); \
+ break; \
+ default: __bad_percpu_size(); \
+ } \
+ ret__ += val; \
+ ret__; \
+})
+
#define percpu_from_op(op, var, constraint) \
({ \
typeof(var) pfo_ret__; \
@@ -300,6 +335,14 @@ do { \
#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)

+#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_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
/*
* Per cpu atomic 64 bit operations are only available under 64 bit.
* 32 bit must fall back to generic operations.
@@ -324,6 +367,9 @@ do { \
#define irqsafe_cpu_or_8(pcp, val) percpu_to_op("or", (pcp), val)
#define irqsafe_cpu_xor_8(pcp, val) percpu_to_op("xor", (pcp), val)

+#define __this_cpu_add_return_8(pcp, val) percpu_add_return_op(pcp, val)
+#define this_cpu_add_return_8(pcp, val) percpu_add_return_op(pcp, val)
+
#endif

/* This is not atomic against other CPUs -- CPU preemption needs to be off */


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