lock: Move cmpxchg() primitives to their own file

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

1 files changed, 78 insertions, 0 deletions

diff --git a/include/cmpxchg.h b/include/cmpxchg.h
new file mode 100644
index 0000000..28911c0
--- /dev/null
+++ b/include/cmpxchg.h
@@ -0,0 +1,78 @@
+/* Copyright 2017 IBM Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * 	http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __CMPXCHG_H
+#define __CMPXCHG_H
+
+#ifndef __TEST__
+/*
+ * Bare cmpxchg, no barriers.
+ */
+static inline uint32_t __cmpxchg32(uint32_t *mem, uint32_t old, uint32_t new)
+{
+	uint32_t prev;
+
+	asm volatile(
+		"# __cmpxchg32		\n"
+		"1:	lwarx	%0,0,%2	\n"
+		"	cmpw	%0,%3	\n"
+		"	bne-	2f	\n"
+		"	stwcx.	%4,0,%2	\n"
+		"	bne-	1b	\n"
+		"2:			\n"
+
+		: "=&r"(prev), "+m"(*mem)
+		: "r"(mem), "r"(old), "r"(new)
+		: "cr0");
+
+	return prev;
+}
+
+static inline uint64_t __cmpxchg64(uint64_t *mem, uint64_t old, uint64_t new)
+{
+	uint64_t prev;
+
+	asm volatile(
+		"# __cmpxchg64		\n"
+		"1:	ldarx	%0,0,%2	\n"
+		"	cmpd	%0,%3	\n"
+		"	bne-	2f	\n"
+		"	stdcx.	%4,0,%2	\n"
+		"	bne-	1b	\n"
+		"2:			\n"
+
+		: "=&r"(prev), "+m"(*mem)
+		: "r"(mem), "r"(old), "r"(new)
+		: "cr0");
+
+	return prev;
+}
+
+static inline uint32_t cmpxchg32(uint32_t *mem, uint32_t old, uint32_t new)
+{
+	uint32_t prev;
+
+	sync();
+	prev = __cmpxchg32(mem, old,new);
+	sync();
+
+	return prev;
+}
+#endif /* __TEST_ */
+
+#endif /* __CMPXCHG_H */
+
+