[PATCH] use smp_mb/wmb/rmb where possible

Replace a number of memory barriers with smp_ variants.  This means we won't
take the unnecessary hit on UP machines.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/timer.c b/kernel/timer.c
index ecb3d67..207aa4f0 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1007,7 +1007,7 @@
 		 * Make sure we read the pid before re-reading the
 		 * parent pointer:
 		 */
-		rmb();
+		smp_rmb();
 		parent = me->group_leader->real_parent;
 		if (old != parent)
 			continue;