From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756396AbbKEB7L (ORCPT ); Wed, 4 Nov 2015 20:59:11 -0500 Received: from e32.co.us.ibm.com ([32.97.110.150]:50026 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754202AbbKEB7J (ORCPT ); Wed, 4 Nov 2015 20:59:09 -0500 X-IBM-Helo: d03dlp02.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Wed, 4 Nov 2015 17:59:03 -0800 From: "Paul E. McKenney" To: Andi Kleen Cc: Peter Zijlstra , Dave Jones , Linux Kernel , Ingo Molnar , Stephane Eranian Subject: Re: perf related lockdep bug Message-ID: <20151105015903.GA14609@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20151104051717.GA6098@codemonkey.org.uk> <20151104102151.GG17308@twins.programming.kicks-ass.net> <20151104102800.GZ11639@twins.programming.kicks-ass.net> <20151104105010.GA11639@twins.programming.kicks-ass.net> <20151104134838.GR29027@linux.vnet.ibm.com> <20151104205836.GZ3533@two.firstfloor.org> <20151105005528.GX29027@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151105005528.GX29027@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15110501-0005-0000-0000-0000198E9A39 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 04, 2015 at 04:55:28PM -0800, Paul E. McKenney wrote: > On Wed, Nov 04, 2015 at 09:58:36PM +0100, Andi Kleen wrote: > > > > I tested my perf stress workload with the patch applied on 4.3, > > unfortunately got a hang again :-/ > > Any diagnostics, sysrq-T output, or whatever? Given that it looks like your hang is happening at runtime, I would guess that the following patch won't help, but who knows? Thanx, Paul ------------------------------------------------------------------------ commit 05faf451f1239a28fcd63bf4b66c0db57d7b13f9 Author: Peter Zijlstra Date: Wed Nov 4 08:22:05 2015 -0800 rcu: Move wakeup out from under rnp->lock This patch removes a potential deadlock hazard by moving the wake_up_process() in rcu_spawn_gp_kthread() out from under rnp->lock. Signed-off-by: Peter Zijlstra Signed-off-by: Paul E. McKenney diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index caf3651fa5c9..183445959d00 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4323,8 +4323,8 @@ static int __init rcu_spawn_gp_kthread(void) sp.sched_priority = kthread_prio; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); } - wake_up_process(t); raw_spin_unlock_irqrestore(&rnp->lock, flags); + wake_up_process(t); } rcu_spawn_nocb_kthreads(); rcu_spawn_boost_kthreads();