This patch uses the rcu_assign_pointer() API to eliminate a number of explicit
memory barriers from code using RCU.  This has been tested successfully on
i386 and ppc64.

Signed-off-by: <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>