[RFC][PATCH 09/31] locking,h8300: Implement atomic_fetch_{add,sub,and,or,xor}()

[Peter Zijlstra <peterz@infradead.org>]

[-- Attachment #1: peterz-atomic-fetch-h8300.patch --]
[-- Type: text/plain, Size: 1918 bytes --]

Implement FETCH-OP atomic primitives, these are very similar to the
existing OP-RETURN primitives we already have, except they return the
value of the atomic variable _before_ modification.

This is especially useful for irreversible operations -- such as
bitops (because it becomes impossible to reconstruct the state prior
to modification).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/h8300/include/asm/atomic.h |   31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

--- a/arch/h8300/include/asm/atomic.h
+++ b/arch/h8300/include/asm/atomic.h
@@ -28,6 +28,19 @@ static inline int atomic_##op##_return(i
 	return ret;						\
 }
 
+#define ATOMIC_FETCH_OP(op, c_op)				\
+static inline int atomic_fetch_##op(int i, atomic_t *v)		\
+{								\
+	h8300flags flags;					\
+	int ret;						\
+								\
+	flags = arch_local_irq_save();				\
+	ret = v->counter;					\
+       	v->counter c_op i;					\
+	arch_local_irq_restore(flags);				\
+	return ret;						\
+}
+
 #define ATOMIC_OP(op, c_op)					\
 static inline void atomic_##op(int i, atomic_t *v)		\
 {								\
@@ -41,17 +54,23 @@ static inline void atomic_##op(int i, at
 ATOMIC_OP_RETURN(add, +=)
 ATOMIC_OP_RETURN(sub, -=)
 
-ATOMIC_OP(and, &=)
-ATOMIC_OP(or,  |=)
-ATOMIC_OP(xor, ^=)
+#define atomic_fetch_or atomic_fetch_or
 
+#define ATOMIC_OPS(op, c_op)					\
+	ATOMIC_OP(op, c_op)					\
+	ATOMIC_FETCH_OP(op, c_op)
+
+ATOMIC_OPS(and, &=)
+ATOMIC_OPS(or,  |=)
+ATOMIC_OPS(xor, ^=)
+ATOMIC_OPS(add, +=)
+ATOMIC_OPS(sub, -=)
+
+#undef ATOMIC_OPS
 #undef ATOMIC_OP_RETURN
 #undef ATOMIC_OP
 
-#define atomic_add(i, v)		(void)atomic_add_return(i, v)
 #define atomic_add_negative(a, v)	(atomic_add_return((a), (v)) < 0)
-
-#define atomic_sub(i, v)		(void)atomic_sub_return(i, v)
 #define atomic_sub_and_test(i, v)	(atomic_sub_return(i, v) == 0)
 
 #define atomic_inc_return(v)		atomic_add_return(1, v)