[PATCH V3 0/3] csky: Optimize with acquire & release for atomic & cmpxchg

guoren
2022-04-17T08:32:25Z

Optimize arch_xchg|cmpxchg|cmpxchg_local with ASM acquire|release
instructions instead of previous C based.

The generic atomic.h used cmpxchg to implement the atomic
operations, it will cause daul loop to reduce the forward
guarantee. The patch implement csky custom atomic operations with
ldex/stex instructions for the best performance.

Important reference commit:
8e86f0b409a4 ("arm64: atomics: fix use of acquire + release for
full barrier semantics")

Changes in V3:
- Add arch_atomic_(fetch_add_unless, inc_unless_negative,
dec_unless_positive, dec_if_positive)

Changes in V2:
- Fixup use of acquire + release for barrier semantics by Rutland.

Guo Ren (3):
csky: cmpxchg: Optimize with acquire & release
csky: atomic: Add custom atomic.h implementation
csky: atomic: Add conditional atomic operations' optimization

arch/csky/include/asm/atomic.h | 249 ++++++++++++++++++++++++++++++++
arch/csky/include/asm/barrier.h | 11 +-
arch/csky/include/asm/cmpxchg.h | 64 +++++++-
3 files changed, 316 insertions(+), 8 deletions(-)
create mode 100644 arch/csky/include/asm/atomic.h

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2.25.1