[RFC][PATCH 19/31] locking,s390: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()

From: Peter Zijlstra
Date: Fri Apr 22 2016 - 05:47:58 EST


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@xxxxxxxxxxxxx>
---
arch/s390/include/asm/atomic.h | 42 +++++++++++++++++++++++++++++++----------
1 file changed, 32 insertions(+), 10 deletions(-)

--- a/arch/s390/include/asm/atomic.h
+++ b/arch/s390/include/asm/atomic.h
@@ -93,6 +93,11 @@ static inline int atomic_add_return(int
return __ATOMIC_LOOP(v, i, __ATOMIC_ADD, __ATOMIC_BARRIER) + i;
}

+static inline int atomic_fetch_add(int i, atomic_t *v)
+{
+ return __ATOMIC_LOOP(v, i, __ATOMIC_ADD, __ATOMIC_BARRIER);
+}
+
static inline void atomic_add(int i, atomic_t *v)
{
#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
@@ -114,22 +119,29 @@ static inline void atomic_add(int i, ato
#define atomic_inc_and_test(_v) (atomic_add_return(1, _v) == 0)
#define atomic_sub(_i, _v) atomic_add(-(int)(_i), _v)
#define atomic_sub_return(_i, _v) atomic_add_return(-(int)(_i), _v)
+#define atomic_fetch_sub(_i, _v) atomic_fetch_add(-(int)(_i), _v)
#define atomic_sub_and_test(_i, _v) (atomic_sub_return(_i, _v) == 0)
#define atomic_dec(_v) atomic_sub(1, _v)
#define atomic_dec_return(_v) atomic_sub_return(1, _v)
#define atomic_dec_and_test(_v) (atomic_sub_return(1, _v) == 0)

-#define ATOMIC_OP(op, OP) \
+#define ATOMIC_OPS(op, OP) \
static inline void atomic_##op(int i, atomic_t *v) \
{ \
__ATOMIC_LOOP(v, i, __ATOMIC_##OP, __ATOMIC_NO_BARRIER); \
+} \
+static inline int atomic_fetch_##op(int i, atomic_t *v) \
+{ \
+ return __ATOMIC_LOOP(v, i, __ATOMIC_##OP, __ATOMIC_BARRIER); \
}

-ATOMIC_OP(and, AND)
-ATOMIC_OP(or, OR)
-ATOMIC_OP(xor, XOR)
+#define atomic_fetch_or atomic_fetch_or
+
+ATOMIC_OPS(and, AND)
+ATOMIC_OPS(or, OR)
+ATOMIC_OPS(xor, XOR)

-#undef ATOMIC_OP
+#undef ATOMIC_OPS

#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

@@ -236,6 +248,11 @@ static inline long long atomic64_add_ret
return __ATOMIC64_LOOP(v, i, __ATOMIC64_ADD, __ATOMIC64_BARRIER) + i;
}

+static inline long long atomic64_fetch_add(long long i, atomic64_t *v)
+{
+ return __ATOMIC64_LOOP(v, i, __ATOMIC64_ADD, __ATOMIC64_BARRIER);
+}
+
static inline void atomic64_add(long long i, atomic64_t *v)
{
#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
@@ -264,17 +281,21 @@ static inline long long atomic64_cmpxchg
return old;
}

-#define ATOMIC64_OP(op, OP) \
+#define ATOMIC64_OPS(op, OP) \
static inline void atomic64_##op(long i, atomic64_t *v) \
{ \
__ATOMIC64_LOOP(v, i, __ATOMIC64_##OP, __ATOMIC64_NO_BARRIER); \
+} \
+static inline long atomic64_fetch_##op(long i, atomic64_t *v) \
+{ \
+ return __ATOMIC64_LOOP(v, i, __ATOMIC64_##OP, __ATOMIC64_BARRIER); \
}

-ATOMIC64_OP(and, AND)
-ATOMIC64_OP(or, OR)
-ATOMIC64_OP(xor, XOR)
+ATOMIC64_OPS(and, AND)
+ATOMIC64_OPS(or, OR)
+ATOMIC64_OPS(xor, XOR)

-#undef ATOMIC64_OP
+#undef ATOMIC64_OPS
#undef __ATOMIC64_LOOP

static inline int atomic64_add_unless(atomic64_t *v, long long i, long long u)
@@ -315,6 +336,7 @@ static inline long long atomic64_dec_if_
#define atomic64_inc_return(_v) atomic64_add_return(1, _v)
#define atomic64_inc_and_test(_v) (atomic64_add_return(1, _v) == 0)
#define atomic64_sub_return(_i, _v) atomic64_add_return(-(long long)(_i), _v)
+#define atomic64_fetch_sub(_i, _v) atomic64_fetch_add(-(long long)(_i), _v)
#define atomic64_sub(_i, _v) atomic64_add(-(long long)(_i), _v)
#define atomic64_sub_and_test(_i, _v) (atomic64_sub_return(_i, _v) == 0)
#define atomic64_dec(_v) atomic64_sub(1, _v)