[PATCH v3 3/6] atomics: Allow architectures to define their own __atomic_op_* helpers

Boqun Feng
2015-10-12T14:15:40Z

Some architectures may have their special barriers for acquire, release
and fence semantics, so that general memory barriers(smp_mb__*_atomic())
in the default __atomic_op_*() may be too strong, so allow architectures
to define their own helpers which can overwrite the default helpers.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
include/linux/atomic.h | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index 27e580d..947c1dc 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -43,20 +43,29 @@ static inline int atomic_read_ctrl(const atomic_t *v)
* The idea here is to build acquire/release variants by adding explicit
* barriers on top of the relaxed variant. In the case where the relaxed
* variant is already fully ordered, no additional barriers are needed.
+ *
+ * Besides, if an arch has a special barrier for acquire/release, it could
+ * implement its own __atomic_op_* and use the same framework for building
+ * variants
*/
+#ifndef __atomic_op_acquire
#define __atomic_op_acquire(op, args...) \
({ \
typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
smp_mb__after_atomic(); \
__ret; \
})
+#endif

+#ifndef __atomic_op_release
#define __atomic_op_release(op, args...) \
({ \
smp_mb__before_atomic(); \
op##_relaxed(args); \
})
+#endif

+#ifndef __atomic_op_fence
#define __atomic_op_fence(op, args...) \
({ \
typeof(op##_relaxed(args)) __ret; \
@@ -65,6 +74,7 @@ static inline int atomic_read_ctrl(const atomic_t *v)
smp_mb__after_atomic(); \
__ret; \
})
+#endif

/* atomic_add_return_relaxed */
#ifndef atomic_add_return_relaxed
--
2.5.3