[RFC 0/5] atomics: powerpc: implement relaxed/acquire/release variants of some atomics

From: Boqun Feng
Date: Thu Aug 27 2015 - 22:48:48 EST


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"

which is now on locking/core branch of tip tree.

By default, the generic code will implement relaxed variants as a full
ordered atomic operation and release/acquire variants as a relaxed variants
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.

Therefore this patchset implements the relaxed/acquire/release variants
based on powerpc memory model and specific barriers. 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 would like to make the code of
these variants at least generated somewhere.

The patchset consists of 5 parts:

1. add trivial tests for the new variants in lib/atomic64_test.c

2. introduce arch_atomic_op_*() helpers as the arch-specific 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

This patchset is based on locking/core branch of tip tree and all patches
are built and boot tested for LE pseries.

Regards,
Boqun

--
2.5.0

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/