[PATCH powerpc/next 2/2] powerpc: Make {cmp}xchg* and their atomic_ versions fully ordered

[Peter Zijlstra]

On Mon, Nov 02, 2015 at 09:30:32AM +0800, Boqun Feng wrote:
> According to memory-barriers.txt, xchg*, cmpxchg* and their atomic_
> versions all need to be fully ordered, however they are now just
> RELEASE+ACQUIRE, which are not fully ordered.
> 
> So also replace PPC_RELEASE_BARRIER and PPC_ACQUIRE_BARRIER with
> PPC_ATOMIC_ENTRY_BARRIER and PPC_ATOMIC_EXIT_BARRIER in
> __{cmp,}xchg_{u32,u64} respectively to guarantee fully ordered semantics
> of atomic{,64}_{cmp,}xchg() and {cmp,}xchg(), as a complement of commit
> b97021f85517 ("powerpc: Fix atomic_xxx_return barrier semantics")
> 
> This patch depends on patch "powerpc: Make value-returning atomics fully
> ordered" for PPC_ATOMIC_ENTRY_BARRIER definition.
> 
> Cc: <stable at vger.kernel.org> # 3.4+
> Signed-off-by: Boqun Feng <boqun.feng at gmail.com>

Acked-by: Peter Zijlstra (Intel) <peterz at infradead.org>