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Subject: [PATCH 12/45] C++: x86: Turn cmpxchg_double() & co. into inline
 template functions
From:   David Howells <dhowells@redhat.com>
To:     linux-kernel@vger.kernel.org
Date:   Sun, 01 Apr 2018 21:41:27 +0100
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Turn cmpxchg_double() 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@redhat.com>
---

 arch/x86/include/asm/cmpxchg.h |   93 +++++++++++++++++++++++++++++++---------
 1 file changed, 71 insertions(+), 22 deletions(-)

diff --git a/arch/x86/include/asm/cmpxchg.h b/arch/x86/include/asm/cmpxchg.h
index 4bbf947c88a2..2ffe1c621eb1 100644
--- a/arch/x86/include/asm/cmpxchg.h
+++ b/arch/x86/include/asm/cmpxchg.h
@@ -180,27 +180,76 @@ static inline P sync_cmpxchg(P *ptr, P old, N rep)
 # include <asm/cmpxchg_64.h>
 #endif
 
-#define __cmpxchg_double(pfx, p1, p2, o1, o2, n1, n2)			\
-({									\
-	bool __ret;							\
-	__typeof__(*(p1)) __old1 = (o1), __new1 = (n1);			\
-	__typeof__(*(p2)) __old2 = (o2), __new2 = (n2);			\
-	BUILD_BUG_ON(sizeof(*(p1)) != sizeof(long));			\
-	BUILD_BUG_ON(sizeof(*(p2)) != sizeof(long));			\
-	VM_BUG_ON((unsigned long)(p1) % (2 * sizeof(long)));		\
-	VM_BUG_ON((unsigned long)((p1) + 1) != (unsigned long)(p2));	\
-	asm volatile(pfx "cmpxchg%c4b %2; sete %0"			\
-		     : "=a" (__ret), "+d" (__old2),			\
-		       "+m" (*(p1)), "+m" (*(p2))			\
-		     : "i" (2 * sizeof(long)), "a" (__old1),		\
-		       "b" (__new1), "c" (__new2));			\
-	__ret;								\
-})
-
-#define cmpxchg_double(p1, p2, o1, o2, n1, n2) \
-	__cmpxchg_double(LOCK_PREFIX, p1, p2, o1, o2, n1, n2)
-
-#define cmpxchg_double_local(p1, p2, o1, o2, n1, n2) \
-	__cmpxchg_double(, p1, p2, o1, o2, n1, n2)
+template <typename P1, typename P2, typename N1, typename N2>
+static inline bool __cmpxchg_double(P1 *p1,  P2 *p2,
+				    P1 old1, P2 old2,
+				    N1 rep1, N2 rep2,
+				    enum cmpxchg_lock lock = __lock_always)
+{
+	bool ret;
+
+	if (sizeof(P1) != sizeof(long)) __cmpxchg_wrong_size();
+	if (sizeof(P2) != sizeof(long))	__cmpxchg_wrong_size();
+
+	//VM_BUG_ON((unsigned long)(p1) % (2 * sizeof(long)));
+	//VM_BUG_ON((unsigned long)((p1) + 1) != (unsigned long)(p2));
+
+	switch (lock) {
+	case __lock_local:
+		asm volatile("cmpxchg%c4b %[ptr1]"
+			     CC_SET(z)
+			     : CC_OUT(z) (ret),
+			       [old2]"+d" (old2),
+			       [ptr1] "+m" (*p1),
+			       [ptr2] "+m" (*p2)
+			     : "i" (2 * sizeof(long)),
+			       [old1] "a" (old1),
+			       [rep1] "b" (rep1),
+			       [rep2] "c" (rep2));
+		break;
+	case __lock_smp:
+		asm volatile(LOCK_PREFIX "cmpxchg%c4b %[ptr1]"
+			     CC_SET(z)
+			     : CC_OUT(z) (ret),
+			       [old2]"+d" (old2),
+			       [ptr1] "+m" (*p1),
+			       [ptr2] "+m" (*p2)
+			     : "i" (2 * sizeof(long)),
+			       [old1] "a" (old1),
+			       [rep1] "b" (rep1),
+			       [rep2] "c" (rep2));
+		break;
+	case __lock_always:
+		asm volatile("lock; cmpxchg%c4b %[ptr1]"
+			     CC_SET(z)
+			     : CC_OUT(z) (ret),
+			       [old2]"+d" (old2),
+			       [ptr1] "+m" (*p1),
+			       [ptr2] "+m" (*p2)
+			     : "i" (2 * sizeof(long)),
+			       [old1] "a" (old1),
+			       [rep1] "b" (rep1),
+			       [rep2] "c" (rep2));
+		break;
+	}
+
+	return ret;
+}
+
+template <typename P1, typename P2, typename N1, typename N2>
+static inline bool cmpxchg_double(P1 *p1,  P2 *p2,
+				  P1 old1, P2 old2,
+				  N1 rep1, N2 rep2)
+{
+	return __cmpxchg_double(p1, p2, old1, old2, rep1, rep2, __lock_always);
+}
+
+template <typename P1, typename P2, typename N1, typename N2>
+static inline bool cmpxchg_double_local(P1 *p1,  P2 *p2,
+					P1 old1, P2 old2,
+					N1 rep1, N2 rep2)
+{
+	return __cmpxchg_double(p1, p2, old1, old2, rep1, rep2, __lock_local);
+}
 
 #endif	/* ASM_X86_CMPXCHG_H */