linux-kernel - [PATCH 13/45] C++: x86: Turn cmpxchg64() & co. into inline template functions

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Date:   Sun, 01 Apr 2018 21:41:33 +0100
From:   David Howells <dhowells@...hat.com>
To:     linux-kernel@...r.kernel.org
Subject: [PATCH 13/45] C++: x86: Turn cmpxchg64() & co. into inline template
 functions

Turn cmpxchg64() and similar functions into inline C++ template functions.
This produces more robust source as the all the casting the C macros
require is then unnecessary.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 arch/x86/include/asm/cmpxchg_64.h |   28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h
index 03cad196a301..55beb7fc036d 100644
--- a/arch/x86/include/asm/cmpxchg_64.h
+++ b/arch/x86/include/asm/cmpxchg_64.h
@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0 */
+/* SPDX-License-Identifier: GPL-2.0 -*- c++ -*- */
 #ifndef _ASM_X86_CMPXCHG_64_H
 #define _ASM_X86_CMPXCHG_64_H
 
@@ -7,17 +7,23 @@ static inline void set_64bit(volatile u64 *ptr, u64 val)
 	*ptr = val;
 }
 
-#define cmpxchg64(ptr, o, n)						\
-({									\
-	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
-	cmpxchg((ptr), (o), (n));					\
-})
+template <typename P, typename N>
+static inline P cmpxchg64(P *ptr, P old, N rep)
+{
+	P ret = old;
+	if (sizeof(P) != 8)
+		__cmpxchg_wrong_size();
+	return cmpxchg(ptr, ret, rep);
+}
 
-#define cmpxchg64_local(ptr, o, n)					\
-({									\
-	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
-	cmpxchg_local((ptr), (o), (n));					\
-})
+template <typename P, typename N>
+static inline P cmpxchg64_local(P *ptr, P old, N rep)
+{
+	P ret = old;
+	if (sizeof(P) != 8)
+		__cmpxchg_wrong_size();
+	return cmpxchg_local(ptr, ret, rep);
+}
 
 #define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX16)