From 3e9f5c70d85060ff0db71826e2048daffec336e7 Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Date: Mon, 3 Nov 2014 18:15:17 -0800
Subject: [PATCH] rcu: Don't spawn rcub kthreads on root rcu_node structure

Now that offlining CPUs no longer moves leaf rcu_node structures'
->blkd_tasks lists to the root, there is no way for the root rcu_node
structure's ->blkd_task list to be nonempty, unless the root node is also
the sole leaf node.  This commit therefore refrains from creating an rcub
kthread for the root rcu_node structure unless it is also the sole leaf.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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