From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753008AbcKIJBI (ORCPT ); Wed, 9 Nov 2016 04:01:08 -0500 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:44272 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750877AbcKIJBH (ORCPT ); Wed, 9 Nov 2016 04:01:07 -0500 X-Original-SENDERIP: 156.147.1.125 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com From: Byungchul Park To: paulmck@linux.vnet.ibm.com, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com Cc: linux-kernel@vger.kernel.org Subject: [PATCH] rcu: Avoid unnecessary contention of rcu node lock Date: Wed, 9 Nov 2016 17:57:13 +0900 Message-Id: <1478681833-23397-1-git-send-email-byungchul.park@lge.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It's unnecessary to try to print stacks of blocked tasks in the case that ndetected == 0. Furthermore, calling rcu_print_detail_task_stall() causes to acquire rnp locks as many times as the number of leaf nodes plus one for root node. It's unnecessary at all in the case. Signed-off-by: Byungchul Park --- kernel/rcu/tree.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 287f468..ab2f743 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1374,6 +1374,9 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) (long)rsp->gpnum, (long)rsp->completed, totqlen); if (ndetected) { rcu_dump_cpu_stacks(rsp); + + /* Complain about tasks blocking the grace period. */ + rcu_print_detail_task_stall(rsp); } else { if (READ_ONCE(rsp->gpnum) != gpnum || READ_ONCE(rsp->completed) == gpnum) { @@ -1390,9 +1393,6 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) } } - /* Complain about tasks blocking the grace period. */ - rcu_print_detail_task_stall(rsp); - rcu_check_gp_kthread_starvation(rsp); panic_on_rcu_stall(); -- 1.9.1