From 09740315d4b914203c25c56e8f8909b4fae7b32d Mon Sep 17 00:00:00 2001
From: Andrea Bastoni <bastoni@cs.unc.edu>
Date: Mon, 19 Apr 2010 19:28:07 -0400
Subject: Add atomic operations on x86_64

---
 include/asm_x86.h | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 64 insertions(+), 2 deletions(-)

diff --git a/include/asm_x86.h b/include/asm_x86.h
index 6636abb..ccc6cce 100644
--- a/include/asm_x86.h
+++ b/include/asm_x86.h
@@ -27,10 +27,10 @@ static inline void sti(void) {
 	asm volatile("sti": : :"memory");
 }
 
-#ifdef __i386__
-
 typedef struct { int counter; } atomic_t;
 
+#ifdef __i386__
+
 #define ATOMIC_INIT(i)	{ (i) }
 
 /**
@@ -78,5 +78,67 @@ static __inline__ int atomic_add_return(int i, atomic_t *v)
 
 #define atomic_inc_return(v)  (atomic_add_return(1,v))
 
+#elif defined(__x86_64__)
+
+/* almost the same as i386, but extra care must be taken when
+ * specifying clobbered registers
+ */
+
+#define ATOMIC_INIT(i)	{ (i) }
+
+/**
+ * atomic_read - read atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically reads the value of @v.
+ */
+static inline int atomic_read(const atomic_t *v)
+{
+	return v->counter;
+}
+
+/**
+ * atomic_set - set atomic variable
+ * @v: pointer of type atomic_t
+ * @i: required value
+ *
+ * Atomically sets the value of @v to @i.
+ */
+static inline void atomic_set(atomic_t *v, int i)
+{
+	v->counter = i;
+}
+
+/**
+ * atomic_add - add integer to atomic variable
+ * @i: integer value to add
+ * @v: pointer of type atomic_t
+ *
+ * Atomically adds @i to @v.
+ */
+static inline void atomic_add(int i, atomic_t *v)
+{
+	asm volatile("lock; addl %1,%0"
+		     : "=m" (v->counter)
+		     : "ir" (i), "m" (v->counter));
+}
+
+/**
+ * atomic_add_return - add and return
+ * @i: integer value to add
+ * @v: pointer of type atomic_t
+ *
+ * Atomically adds @i to @v and returns @i + @v
+ */
+static inline int atomic_add_return(int i, atomic_t *v)
+{
+	int __i = i;
+	asm volatile("lock; xaddl %0, %1"
+		     : "+r" (i), "+m" (v->counter)
+		     : : "memory");
+	return i + __i;
+}
+
+#define atomic_inc_return(v)  (atomic_add_return(1, v))
 
 #endif
-- 
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