Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1255786

[PATCH tip/locking/core v5 3/6] atomics: Allow architectures to define their own __atomic_op_* helpers

Show all headers | View raw

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
-- 
2.6.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[PATCH tip/locking/core v5 3/6] atomics: Allow architectures to define their own __atomic_op_* helpers Boqun Feng <boqun.feng@gmail.com> - 2015-10-26 11:00 +0100

csiph-web