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atomics: Allow architectures to define their own __atomic_op_* helpers

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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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Boqun Feng 2015-12-15 22:24:14 +08:00 committed by Michael Ellerman
parent 78c1cffdab
commit e1ab7f39d7
1 changed files with 10 additions and 0 deletions
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10
include/linux/atomic.h
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@ -34,20 +34,29 @@
* 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; \
@ -56,6 +65,7 @@
smp_mb__after_atomic(); \
__ret; \
})
#endif
/* atomic_add_return_relaxed */
#ifndef atomic_add_return_relaxed