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powerpc: atomic: Implement acquire/release/relaxed variants for cmpxchg

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Implement cmpxchg{,64}_relaxed and atomic{,64}_cmpxchg_relaxed, based on
which _release variants can be built.

To avoid superfluous barriers in _acquire variants, we implement these
operations with assembly code rather use __atomic_op_acquire() to build
them automatically.

For the same reason, we keep the assembly implementation of fully
ordered cmpxchg operations.

However, we don't do the similar for _release, because that will require
putting barriers in the middle of ll/sc loops, which is probably a bad
idea.

Note cmpxchg{,64}_relaxed and atomic{,64}_cmpxchg_relaxed are not
compiler barriers.

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 22:24:17 +08:00
committed by Michael Ellerman
parent 26760fc19a
commit 56c08e6d22
2 changed files with 158 additions and 1 deletions
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10
arch/powerpc/include/asm/atomic.h
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@@ -176,6 +176,11 @@ static __inline__ int atomic_dec_return_relaxed(atomic_t *v)
#define atomic_dec_return_relaxed atomic_dec_return_relaxed
#define atomic_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
#define atomic_cmpxchg_relaxed(v, o, n) \
cmpxchg_relaxed(&((v)->counter), (o), (n))
#define atomic_cmpxchg_acquire(v, o, n) \
cmpxchg_acquire(&((v)->counter), (o), (n))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
#define atomic_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
@@ -444,6 +449,11 @@ static __inline__ long atomic64_dec_if_positive(atomic64_t *v)
}
#define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
#define atomic64_cmpxchg_relaxed(v, o, n) \
cmpxchg_relaxed(&((v)->counter), (o), (n))
#define atomic64_cmpxchg_acquire(v, o, n) \
cmpxchg_acquire(&((v)->counter), (o), (n))
#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
#define atomic64_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))