linux-kernel - [PATCH 2/6] x86: Support for this_cpu_add, sub, dec, inc

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Date:	Sat, 18 Dec 2010 16:24:08 +0100
From:	Tejun Heo <tj@...nel.org>
To:	penberg@...helsinki.fi, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, eric.dumazet@...il.com,
	hpa@...or.com, mathieu.desnoyers@...icios.com
Cc:	Christoph Lameter <cl@...ux.com>, Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/6] x86: Support for this_cpu_add, sub, dec, inc_return

From: Christoph Lameter <cl@...ux.com>

Supply an implementation for x86 in order to generate more efficient code.

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

tj: - Dropped unused typedef from percpu_add_return_op().
    - Renamed ret__ to paro_ret__ in percpu_add_return_op().
    - Minor indentation adjustments.

Acked-by: H. Peter Anvin <hpa@...or.com>
Signed-off-by: Christoph Lameter <cl@...ux.com>
Signed-off-by: Tejun Heo <tj@...nel.org>
---
 arch/x86/include/asm/percpu.h |   43 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index f899e01..38f9e96 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -177,6 +177,39 @@ do {									\
 	}								\
 } while (0)
 
+/*
+ * Add return operation
+ */
+#define percpu_add_return_op(var, val)					\
+({									\
+	typeof(var) paro_ret__ = val;					\
+	switch (sizeof(var)) {						\
+	case 1:								\
+		asm("xaddb %0, "__percpu_arg(1)				\
+			    : "+q" (paro_ret__), "+m" (var)		\
+			    : : "memory");				\
+		break;							\
+	case 2:								\
+		asm("xaddw %0, "__percpu_arg(1)				\
+			    : "+r" (paro_ret__), "+m" (var)		\
+			    : : "memory");				\
+		break;							\
+	case 4:								\
+		asm("xaddl %0, "__percpu_arg(1)				\
+			    : "+r" (paro_ret__), "+m" (var)		\
+			    : : "memory");				\
+		break;							\
+	case 8:								\
+		asm("xaddq %0, "__percpu_arg(1)				\
+			    : "+re" (paro_ret__), "+m" (var)		\
+			    : : "memory");				\
+		break;							\
+	default: __bad_percpu_size();					\
+	}								\
+	paro_ret__ += val;						\
+	paro_ret__;							\
+})
+
 #define percpu_from_op(op, var, constraint)		\
 ({							\
 	typeof(var) pfo_ret__;				\
@@ -300,6 +333,14 @@ 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 +365,8 @@ 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 */
-- 
1.7.1

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