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) <[email protected]>
---
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)
On Fri, 22 Apr 2016 11:04:32 +0200
Peter Zijlstra <[email protected]> wrote:
> 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) <[email protected]>
> ---
> arch/s390/include/asm/atomic.h | 42 +++++++++++++++++++++++++++++++----------
> 1 file changed, 32 insertions(+), 10 deletions(-)
That looks good, the code compiles and the functions are generated correctly.
We will know for sure if it works after the first user of these new functions
hit the kernel.
Acked-by: Martin Schwidefsky <[email protected]>
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
On Mon, Apr 25, 2016 at 10:06:25AM +0200, Martin Schwidefsky wrote:
> On Fri, 22 Apr 2016 11:04:32 +0200
> Peter Zijlstra <[email protected]> wrote:
>
> > 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) <[email protected]>
> > ---
> > arch/s390/include/asm/atomic.h | 42 +++++++++++++++++++++++++++++++----------
> > 1 file changed, 32 insertions(+), 10 deletions(-)
>
> That looks good, the code compiles and the functions are generated correctly.
> We will know for sure if it works after the first user of these new functions
> hit the kernel.
So we already have an atomic_fetch_or() user in the kernel, and this
series adds an atomic_fetch_add_acquire() user.
But yes, we'll undoubtedly grow more over time :-)
> Acked-by: Martin Schwidefsky <[email protected]>
Thanks!