From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932666AbbANHlR (ORCPT ); Wed, 14 Jan 2015 02:41:17 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:59025 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932173AbbANHlJ (ORCPT ); Wed, 14 Jan 2015 02:41:09 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , Chuansheng Liu , Peter Zijlstra , Ingo Molnar Subject: [PATCH 3.18 115/150] sched: Add missing rcu protection to wake_up_all_idle_cpus Date: Tue, 13 Jan 2015 23:23:06 -0800 Message-Id: <20150114072101.068284286@linuxfoundation.org> X-Mailer: git-send-email 2.2.2 In-Reply-To: <20150114072055.842408181@linuxfoundation.org> References: <20150114072055.842408181@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit fd7de1e8d5b2b2b35e71332fafb899f584597150 upstream. Locklessly doing is_idle_task(rq->curr) is only okay because of RCU protection. The older variant of the broken code checked rq->curr == rq->idle instead and therefore didn't need RCU. Fixes: f6be8af1c95d ("sched: Add new API wake_up_if_idle() to wake up the idle cpu") Signed-off-by: Andy Lutomirski Reviewed-by: Chuansheng Liu Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/729365dddca178506dfd0a9451006344cd6808bc.1417277372.git.luto@amacapital.net Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/sched/core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1623,8 +1623,10 @@ void wake_up_if_idle(int cpu) struct rq *rq = cpu_rq(cpu); unsigned long flags; - if (!is_idle_task(rq->curr)) - return; + rcu_read_lock(); + + if (!is_idle_task(rcu_dereference(rq->curr))) + goto out; if (set_nr_if_polling(rq->idle)) { trace_sched_wake_idle_without_ipi(cpu); @@ -1635,6 +1637,9 @@ void wake_up_if_idle(int cpu) /* Else cpu is not in idle, do nothing here */ raw_spin_unlock_irqrestore(&rq->lock, flags); } + +out: + rcu_read_unlock(); } bool cpus_share_cache(int this_cpu, int that_cpu)