From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755767AbaKERnB (ORCPT ); Wed, 5 Nov 2014 12:43:01 -0500 Received: from e38.co.us.ibm.com ([32.97.110.159]:47034 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754596AbaKERlp (ORCPT ); Wed, 5 Nov 2014 12:41:45 -0500 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 09/10] rcu: Don't spawn rcub kthreads on root rcu_node structure Date: Wed, 5 Nov 2014 09:41:33 -0800 Message-Id: <1415209294-2534-9-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1415209294-2534-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20141105174109.GA1306@linux.vnet.ibm.com> <1415209294-2534-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14110517-0029-0000-0000-000005661B85 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" 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 --- kernel/rcu/tree_plugin.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 65786864dcfb..fb05d963eaaa 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1371,12 +1371,8 @@ 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) -- 1.8.1.5