Commit 3e9f5c70 authored Nov 03, 2014 by Paul E. McKenney

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>

parent 96e92021

kernel/rcu/tree_plugin.h

+2 −6

Original line number	Diff line number	Diff line
		@@ -1352,13 +1352,9 @@ static void __init rcu_spawn_boost_kthreads(void)
		for_each_possible_cpu(cpu)
		per_cpu(rcu_cpu_has_work, cpu) = 0;
		BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec));
		rnp = rcu_get_root(rcu_state_p);
		(void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
		if (NUM_RCU_NODES > 1) {
		rcu_for_each_leaf_node(rcu_state_p, rnp)
		(void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
		}
		}

		static void rcu_prepare_kthreads(int cpu)
		{

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