[tip:x86/spinlocks] x86, cmpxchg: Use __compiletime_error() to make usage messages a bit nicer

[tip-bot for Jeremy Fitzhardinge]

Commit-ID:  61e2cd0acc248c14793cefd7e23e209be9e0b70d
Gitweb:     http://git.kernel.org/tip/61e2cd0acc248c14793cefd7e23e209be9e0b70d
Author:     Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
AuthorDate: Mon, 29 Aug 2011 14:47:58 -0700
Committer:  H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Mon, 29 Aug 2011 17:20:40 -0700

x86, cmpxchg: Use __compiletime_error() to make usage messages a bit nicer

Use __compiletime_error() to produce a compile-time error rather than
link-time, where available.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/4E5BCC40.3030501@xxxxxxxx
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/cmpxchg.h |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/cmpxchg.h b/arch/x86/include/asm/cmpxchg.h
index 0d0d9cd..5d3acdf 100644
--- a/arch/x86/include/asm/cmpxchg.h
+++ b/arch/x86/include/asm/cmpxchg.h
@@ -1,12 +1,19 @@
 #ifndef ASM_X86_CMPXCHG_H
 #define ASM_X86_CMPXCHG_H
 
+#include <linux/compiler.h>
 #include <asm/alternative.h> /* Provides LOCK_PREFIX */
 
-/* Non-existant functions to indicate usage errors at link time. */
-extern void __xchg_wrong_size(void);
-extern void __cmpxchg_wrong_size(void);
-extern void __xadd_wrong_size(void);
+/*
+ * Non-existant functions to indicate usage errors at link time
+ * (or compile-time if the compiler implements __compiletime_error().
+ */
+extern void __xchg_wrong_size(void)
+	__compiletime_error("Bad argument size for xchg");
+extern void __cmpxchg_wrong_size(void)
+	__compiletime_error("Bad argument size for cmpxchg");
+extern void __xadd_wrong_size(void)
+	__compiletime_error("Bad argument size for xadd");
 
 /*
  * Constants for operation sizes. On 32-bit, the 64-bit size it set to
--
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