From: Paul E. McKenney Date: Tue, 4 Nov 2014 02:15:17 +0000 (-0800) Subject: rcu: Don't spawn rcub kthreads on root rcu_node structure X-Git-Tag: v4.0-rc1~165^2^2^3~6 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=3e9f5c70d85060ff0db71826e2048daffec336e7;p=karo-tx-linux.git 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 --- diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index bcc6d9134d47..3e64bb197b1a 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1352,12 +1352,8 @@ 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); - } + 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)