Some architectures may have their special barriers for acquire, release
and fence semantics, general memory barriers(smp_mb__*_atomic()) in
__atomic_op_*() may be too strong, so arch_atomic_op_*() helpers are
introduced for architectures to provide their own version helpers to
build different variants based on _relaxed variants.
Signed-off-by: Boqun Feng <boqun.f...@gmail.com>
---
include/linux/atomic.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index 00a5763..622255b 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -34,20 +34,33 @@
* 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 arch_atomic_op_* and use the same framework for building
+ * variants
*/
+#ifndef arch_atomic_op_acquire
#define __atomic_op_acquire(op, args...) \
({ \
typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
smp_mb__after_atomic(); \
__ret; \
})
+#else
+#define __atomic_op_acquire arch_atomic_op_acquire
+#endif
+#ifndef arch_atomic_op_release
#define __atomic_op_release(op, args...) \
({ \
smp_mb__before_atomic(); \
op##_relaxed(args); \
})
+#else
+#define __atomic_op_release arch_atomic_op_release
+#endif
+#ifndef arch_atomic_op_fence
#define __atomic_op_fence(op, args...) \
({ \
typeof(op##_relaxed(args)) __ret; \
@@ -56,6 +69,9 @@
smp_mb__after_atomic(); \
__ret; \
})
+#else
+#define __atomic_op_fence arch_atomic_op_fence
+#endif
/* atomic_add_return_relaxed */
#ifndef atomic_add_return_relaxed
--
2.5.0
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