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Subject[PATCH 07/15] x86: add xadd helper macro
Date
From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

Add a common xadd implementation.

This has the side effect of generating a bad instruction if you try to
use it on a 64-bit value on a 32-bit system - but don't do that.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
arch/x86/include/asm/cmpxchg.h | 32 ++++++++++++++++++++++++++++++++
1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/cmpxchg.h b/arch/x86/include/asm/cmpxchg.h
index a460fa0..b771cdb 100644
--- a/arch/x86/include/asm/cmpxchg.h
+++ b/arch/x86/include/asm/cmpxchg.h
@@ -1,5 +1,37 @@
+#ifndef ASM_X86_CMPXCHG_H
+#define ASM_X86_CMPXCHG_H
+
#ifdef CONFIG_X86_32
# include "cmpxchg_32.h"
#else
# include "cmpxchg_64.h"
#endif
+
+
+#define xadd(ptr, inc) \
+ do { \
+ switch (sizeof(*(ptr))) { \
+ case 1: \
+ asm volatile (LOCK_PREFIX "xaddb %b0, %1\n" \
+ : "+r" (inc), "+m" (*(ptr)) \
+ : : "memory", "cc"); \
+ break; \
+ case 2: \
+ asm volatile (LOCK_PREFIX "xaddw %w0, %1\n" \
+ : "+r" (inc), "+m" (*(ptr)) \
+ : : "memory", "cc"); \
+ break; \
+ case 4: \
+ asm volatile (LOCK_PREFIX "xaddl %0, %1\n" \
+ : "+r" (inc), "+m" (*(ptr)) \
+ : : "memory", "cc"); \
+ break; \
+ case 8: \
+ asm volatile (LOCK_PREFIX "xaddq %q0, %1\n" \
+ : "+r" (inc), "+m" (*(ptr)) \
+ : : "memory", "cc"); \
+ break; \
+ } \
+ } while(0)
+
+#endif /* ASM_X86_CMPXCHG_H */
--
1.7.6


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