[RFC v2 0/7] atomics: powerpc: Implement relaxed/acquire/release variants of some atomics
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STALE4036d
SUPERSEDED
From: Boqun Feng <hidden>
Date: 2015-09-16 15:50:00
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Subsystem:
atomic infrastructure, library code, linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Will Deacon, Peter Zijlstra, Boqun Feng, Andrew Morton, Madhavan Srinivasan, Linus Torvalds
Status: Superseded by v5 (posted 2015-10-26). [go to v5]
Revision v2 (5 revisions archived).
Revisions (5)
Link for v1: https://lkml.org/lkml/2015/8/27/798 Changes since v1: * avoid to introduce macro arch_atomic_op_*() * also fix the problem that cmpxchg, xchg and their atomic_ versions are not full barriers in PPC implementation. * rebase on v4.3-rc1 Relaxed/acquire/release variants of atomic operations {add,sub}_return and {cmp,}xchg are introduced by commit: "atomics: add acquire/release/relaxed variants of some atomic operations" By default, the generic code will implement a relaxed variant as a full ordered atomic operation and release/acquire a variant as a relaxed variant with a necessary general barrier before or after. On powerpc, which has a weak memory order model, a relaxed variant can be implemented more lightweightly than a full ordered one. Further more, release and acquire variants can be implemented with arch-specific lightweight barriers. Besides, cmpxchg, xchg and their atomic_ versions are only RELEASE+ACQUIRE rather that full barriers in current PPC implementation, which is incorrect according to memory-barriers.txt. Therefore this patchset implements the relaxed/acquire/release variants based on powerpc memory model and specific barriers, and fix cmpxchg, xchg and their atomic_ versions. A trivial test for these new variants is also included in this series, because some of these variants are not used in kernel for now, I think is a good idea to at least generate the code for these variants somewhere. The patchset consists of 7 parts: 1. Add trivial tests for the new variants in lib/atomic64_test.c 2. Allow architectures to define their own __atomic_op_*() helpers to build other variants based on relaxed. 3. Implement atomic{,64}_{add,sub}_return_* variants 4. Implement xchg_* and atomic{,64}_xchg_* variants 5. Implement cmpxchg_* atomic{,64}_cmpxchg_* variants 6. Make atomic{,64}_xchg and xchg full barriers 7. Make atomic{,64}_cmpxchg and cmpxchg full barriers This patchset is based on v4.3-rc1 and all patches are built and boot tested for little endian powernv and pseries, and also tested by 0day. Looking forward to any suggestion, question and comment ;-) Regards, Boqun