rcu: Initialize multi-level RCU grace periods holding locks

Prior implementations initialized the root and any internal
nodes without holding locks, then initialized the leaves
holding locks.

This is a false economy, as the leaf nodes will usually greatly
outnumber the root and internal nodes.  Acquiring locks on all
nodes is conceptually much simpler as well.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josht@linux.vnet.ibm.com
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
LKML-Reference: <12524504773190-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>