[PATCH] x86-64: add atomic64_t

Add an atomic64_t type to x86-64.

Not used right now, but may be useful in the future, e.g.  for rss together
with C.Lameter's page fault scalability patches.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-x86_64/atomic.h

@@ -178,6 +178,166 @@ static __inline__ int atomic_add_negative(int i, atomic_t *v)
 	return c;
 }
 
+/* An 64bit atomic type */
+
+typedef struct { volatile long counter; } atomic64_t;
+
+#define ATOMIC64_INIT(i)	{ (i) }
+
+/**
+ * atomic64_read - read atomic64 variable
+ * @v: pointer of type atomic64_t
+ *
+ * Atomically reads the value of @v.
+ * Doesn't imply a read memory barrier.
+ */
+#define atomic64_read(v)		((v)->counter)
+
+/**
+ * atomic64_set - set atomic64 variable
+ * @v: pointer to type atomic64_t
+ * @i: required value
+ *
+ * Atomically sets the value of @v to @i.
+ */
+#define atomic64_set(v,i)		(((v)->counter) = (i))
+
+/**
+ * atomic64_add - add integer to atomic64 variable
+ * @i: integer value to add
+ * @v: pointer to type atomic64_t
+ *
+ * Atomically adds @i to @v.
+ */
+static __inline__ void atomic64_add(long i, atomic64_t *v)
+{
+	__asm__ __volatile__(
+		LOCK "addq %1,%0"
+		:"=m" (v->counter)
+		:"ir" (i), "m" (v->counter));
+}
+
+/**
+ * atomic64_sub - subtract the atomic64 variable
+ * @i: integer value to subtract
+ * @v: pointer to type atomic64_t
+ *
+ * Atomically subtracts @i from @v.
+ */
+static __inline__ void atomic64_sub(long i, atomic64_t *v)
+{
+	__asm__ __volatile__(
+		LOCK "subq %1,%0"
+		:"=m" (v->counter)
+		:"ir" (i), "m" (v->counter));
+}
+
+/**
+ * atomic64_sub_and_test - subtract value from variable and test result
+ * @i: integer value to subtract
+ * @v: pointer to type atomic64_t
+ *
+ * Atomically subtracts @i from @v and returns
+ * true if the result is zero, or false for all
+ * other cases.
+ */
+static __inline__ int atomic64_sub_and_test(long i, atomic64_t *v)
+{
+	unsigned char c;
+
+	__asm__ __volatile__(
+		LOCK "subq %2,%0; sete %1"
+		:"=m" (v->counter), "=qm" (c)
+		:"ir" (i), "m" (v->counter) : "memory");
+	return c;
+}
+
+/**
+ * atomic64_inc - increment atomic64 variable
+ * @v: pointer to type atomic64_t
+ *
+ * Atomically increments @v by 1.
+ */
+static __inline__ void atomic64_inc(atomic64_t *v)
+{
+	__asm__ __volatile__(
+		LOCK "incq %0"
+		:"=m" (v->counter)
+		:"m" (v->counter));
+}
+
+/**
+ * atomic64_dec - decrement atomic64 variable
+ * @v: pointer to type atomic64_t
+ *
+ * Atomically decrements @v by 1.
+ */
+static __inline__ void atomic64_dec(atomic64_t *v)
+{
+	__asm__ __volatile__(
+		LOCK "decq %0"
+		:"=m" (v->counter)
+		:"m" (v->counter));
+}
+
+/**
+ * atomic64_dec_and_test - decrement and test
+ * @v: pointer to type atomic64_t
+ *
+ * Atomically decrements @v by 1 and
+ * returns true if the result is 0, or false for all other
+ * cases.
+ */
+static __inline__ int atomic64_dec_and_test(atomic64_t *v)
+{
+	unsigned char c;
+
+	__asm__ __volatile__(
+		LOCK "decq %0; sete %1"
+		:"=m" (v->counter), "=qm" (c)
+		:"m" (v->counter) : "memory");
+	return c != 0;
+}
+
+/**
+ * atomic64_inc_and_test - increment and test
+ * @v: pointer to type atomic64_t
+ *
+ * Atomically increments @v by 1
+ * and returns true if the result is zero, or false for all
+ * other cases.
+ */
+static __inline__ int atomic64_inc_and_test(atomic64_t *v)
+{
+	unsigned char c;
+
+	__asm__ __volatile__(
+		LOCK "incq %0; sete %1"
+		:"=m" (v->counter), "=qm" (c)
+		:"m" (v->counter) : "memory");
+	return c != 0;
+}
+
+/**
+ * atomic64_add_negative - add and test if negative
+ * @v: pointer to atomic64_t
+ * @i: integer value to add
+ *
+ * Atomically adds @i to @v and returns true
+ * if the result is negative, or false when
+ * result is greater than or equal to zero.
+ */
+static __inline__ long atomic64_add_negative(long i, atomic64_t *v)
+{
+	unsigned char c;
+
+	__asm__ __volatile__(
+		LOCK "addq %2,%0; sets %1"
+		:"=m" (v->counter), "=qm" (c)
+		:"ir" (i), "m" (v->counter) : "memory");
+	return c;
+}
+
 /* These are x86-specific, used by some header files */
 #define atomic_clear_mask(mask, addr) \
 __asm__ __volatile__(LOCK "andl %0,%1" \