From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753779Ab1FOISO (ORCPT ); Wed, 15 Jun 2011 04:18:14 -0400 Received: from merlin.infradead.org ([205.233.59.134]:40724 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752201Ab1FOISL convert rfc822-to-8bit (ORCPT ); Wed, 15 Jun 2011 04:18:11 -0400 Subject: Re: [PATCH 2/2] sched: Check if lowest_mask is initialized in find_lowest_rq From: Peter Zijlstra To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Paul McKenney , Andrew Theurer In-Reply-To: <20110614223657.824872966@goodmis.org> References: <20110614223623.876681637@goodmis.org> <20110614223657.824872966@goodmis.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Wed, 15 Jun 2011 10:17:41 +0200 Message-ID: <1308125861.15315.2.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-06-14 at 18:36 -0400, Steven Rostedt wrote: > plain text document attachment > (0002-sched-Check-if-lowest_mask-is-initialized-in-find_lo.patch) > From: Steven Rostedt > > On system boot up, the lowest_mask is initialized with early_initcall. > But RT tasks may wake up on other early_initcall callers before the > lowest_mask is initialized, causing a system crash. > > The commit d72bce0e67 rcu: Cure load woes > was the first commit to wake up RT tasks in early init. Before this > commit this bug should not happen. > Acked-by: Peter Zijlstra > Cc: Paul McKenney > Reported-by: Andrew Theurer > Tested-by: Andrew Theurer > Link: http://lkml.kernel.org/r/1308014683.9218.107.camel@gandalf.stny.rr.com > Signed-off-by: Steven Rostedt > --- > kernel/sched_rt.c | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c > index 9b8d5dc..10d0182 100644 > --- a/kernel/sched_rt.c > +++ b/kernel/sched_rt.c > @@ -1239,6 +1239,10 @@ static int find_lowest_rq(struct task_struct *task) > int this_cpu = smp_processor_id(); > int cpu = task_cpu(task); > > + /* Make sure the mask is initialized first */ > + if (unlikely(!lowest_mask)) > + return -1; > + > if (task->rt.nr_cpus_allowed == 1) > return -1; /* No other targets possible */ >