From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751506Ab1LHPR0 (ORCPT ); Thu, 8 Dec 2011 10:17:26 -0500 Received: from terminus.zytor.com ([198.137.202.10]:59477 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751260Ab1LHPRY (ORCPT ); Thu, 8 Dec 2011 10:17:24 -0500 Date: Thu, 8 Dec 2011 07:16:48 -0800 From: tip-bot for Peter Zijlstra Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, peterz@infradead.org, suresh.b.siddha@intel.com, tglx@linutronix.de, yong.zhang0@gmail.com, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, peterz@infradead.org, suresh.b.siddha@intel.com, tglx@linutronix.de, yong.zhang0@gmail.com, mingo@elte.hu In-Reply-To: <1323264728.32012.107.camel@twins> References: <1323264728.32012.107.camel@twins> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched, nohz: Fix missing RCU read lock Git-Commit-ID: 067491b7313c41f49607fce782d29344d1472587 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.6 (terminus.zytor.com [127.0.0.1]); Thu, 08 Dec 2011 07:16:55 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 067491b7313c41f49607fce782d29344d1472587 Gitweb: http://git.kernel.org/tip/067491b7313c41f49607fce782d29344d1472587 Author: Peter Zijlstra AuthorDate: Wed, 7 Dec 2011 14:32:08 +0100 Committer: Ingo Molnar CommitDate: Thu, 8 Dec 2011 05:45:48 +0100 sched, nohz: Fix missing RCU read lock Yong Zhang reported: > [ INFO: suspicious RCU usage. ] > kernel/sched/fair.c:5091 suspicious rcu_dereference_check() usage! This is due to the sched_domain stuff being RCU protected and commit 0b005cf5 ("sched, nohz: Implement sched group, domain aware nohz idle load balancing") overlooking this fact. The sd variable only lives inside the for_each_domain() block, so we only need to wrap that. Reported-by: Yong Zhang Tested-by: Yong Zhang Signed-off-by: Peter Zijlstra Cc: Suresh Siddha Link: http://lkml.kernel.org/r/1323264728.32012.107.camel@twins Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 6482136..a4d2b7a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5088,23 +5088,28 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu) if (rq->nr_running >= 2) goto need_kick; + rcu_read_lock(); for_each_domain(cpu, sd) { struct sched_group *sg = sd->groups; struct sched_group_power *sgp = sg->sgp; int nr_busy = atomic_read(&sgp->nr_busy_cpus); if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1) - goto need_kick; + goto need_kick_unlock; if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight && (cpumask_first_and(nohz.idle_cpus_mask, sched_domain_span(sd)) < cpu)) - goto need_kick; + goto need_kick_unlock; if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING))) break; } + rcu_read_unlock(); return 0; + +need_kick_unlock: + rcu_read_unlock(); need_kick: return 1; }