[PATCH v2 0/7] Add generic support for relaxed atomics

Will Deacon
2015-07-16T15:32:31Z

Hi all,

This is version two of the patches I previously posted here:

https://lwn.net/Articles/650862/

The series adds support for a family of relaxed atomics to the kernel.
More specifically:

- acquire/release/relaxed flavours of xchg, cmpxchg and {add,sub}_return
- atomic_read_acquire
- atomic_set_release

This came out of a separate patch series porting the (barrier-heavy)
qrwlock code to arm64. Rather than have arch-specific hooks littered
around the place, it makes more sense to define a core set of relaxed
atomics that can be used regardless of architecture.

Changes since v1 include:

- Added macros to construct acquire/release/fence variants from a
relaxed variant + barrier macros

- Ported ARM as a proof of concept (with a negative diffstat!)

Build tested on ARM, arm64, PowerPC and x86.

All feedback welcome,

Will

--->8

Will Deacon (7):
atomics: add acquire/release/relaxed variants of some atomic
operations
asm-generic: rework atomic-long.h to avoid bulk code duplication
asm-generic: add relaxed/acquire/release variants for atomic_long_t
lockref: remove homebrew cmpxchg64_relaxed macro definition
locking/qrwlock: make use of acquire/release/relaxed atomics
include/llist: use linux/atomic.h instead of asm/cmpxchg.h
ARM: atomics: define our SMP atomics in terms of _relaxed operations

arch/arm/include/asm/atomic.h | 37 ++---
arch/arm/include/asm/cmpxchg.h | 47 +-----
include/asm-generic/atomic-long.h | 263 ++++++++++++--------------------
include/asm-generic/qrwlock.h | 13 +-
include/linux/atomic.h | 312 ++++++++++++++++++++++++++++++++++++++
include/linux/llist.h | 2 +-
kernel/locking/qrwlock.c | 12 +-
lib/lockref.c | 8 -
8 files changed, 442 insertions(+), 252 deletions(-)

--
2.1.4