[PATCH RFC tip/core/rcu 01/28] powerpc: Strengthen value-returning-atomics memory barriers

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

The trailing isync/lwsync in PowerPC value-returning atomics needs
to be a sync in order to provide the required ordering properties.
The leading lwsync/eieio can remain, as the remainder of the required
ordering guarantees are provided by the atomic instructions: Any
reordering will cause the stwcx to fail, which will result in a retry.

This commit provides the needed adjustment.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: anton@samba.org
Cc: benh@kernel.crashing.org
Cc: paulus@samba.org
---
 arch/powerpc/include/asm/synch.h |    6 +-----
 1 files changed, 1 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/synch.h b/arch/powerpc/include/asm/synch.h
index d7cab44..4d97fbe 100644
--- a/arch/powerpc/include/asm/synch.h
+++ b/arch/powerpc/include/asm/synch.h
@@ -37,11 +37,7 @@ static inline void isync(void)
 #endif
 
 #ifdef CONFIG_SMP
-#define __PPC_ACQUIRE_BARRIER				\
-	START_LWSYNC_SECTION(97);			\
-	isync;						\
-	MAKE_LWSYNC_SECTION_ENTRY(97, __lwsync_fixup);
-#define PPC_ACQUIRE_BARRIER	"\n" stringify_in_c(__PPC_ACQUIRE_BARRIER)
+#define PPC_ACQUIRE_BARRIER	"\n" stringify_in_c(sync;)
 #define PPC_RELEASE_BARRIER	stringify_in_c(LWSYNC) "\n"
 #else
 #define PPC_ACQUIRE_BARRIER
-- 
1.7.3.2