From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754566Ab1EPWHP (ORCPT ); Mon, 16 May 2011 18:07:15 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:38487 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753607Ab1EPWHN (ORCPT ); Mon, 16 May 2011 18:07:13 -0400 Date: Mon, 16 May 2011 15:07:10 -0700 From: "Paul E. McKenney" To: Ingo Molnar Cc: Yinghai Lu , linux-kernel@vger.kernel.org Subject: Re: [GIT PULL rcu/next] rcu commits for 2.6.40 Message-ID: <20110516220710.GA6139@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110513131218.GA7669@elte.hu> <20110513141431.GV2258@linux.vnet.ibm.com> <20110513150744.GE32688@elte.hu> <20110513162646.GW2258@linux.vnet.ibm.com> <20110516070808.GC24836@elte.hu> <20110516074822.GE2573@linux.vnet.ibm.com> <20110516115148.GA2421@elte.hu> <20110516122329.GA29356@elte.hu> <20110516143005.GA25245@elte.hu> <20110516213331.GK2573@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110516213331.GK2573@linux.vnet.ibm.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 16, 2011 at 02:33:31PM -0700, Paul E. McKenney wrote: > On Mon, May 16, 2011 at 04:30:05PM +0200, Ingo Molnar wrote: > > > > * Ingo Molnar wrote: > > > > > > I'll try it in any case. > > > > > > oh, this was a new iteration, mea culpa! > > > > > > And yes, it solves all problems for me as well. Mind pushing it as a fix? :-) > > > > FYI, i am also getting the warning below with a defconfig. > > Yep, this is me whining that rcu_enter_nohz() was called before the > irq nesting count (->dynticks_nesting) had dropped to zero. In other > words, either I am mis-counting interrupts or we entered some irq > handler and then somehow never left it, but still managed to get > to process-level execution. Most likely that I am miscounting > somehow. > > I suppose that I could remove the WARN_ON_ONCE() and pretend that all > was well, but... ;-) Actually, your test did prove something very interesting. I have been suspecting NMIs, but since the patch you just tested commented out rcu_nmi_enter() and rcu_nmi_exit() completely, we know that there is some bug outside of these two functions. So if I am miscounting nesting levels, I must be doing soe in rcu_enter_nohz(), rcu_exit_nohz(), rcu_irq_enter(), or rcu_irq_exit(). Or some combination of those four. Thanx, Paul > > Ingo > > > > initcall init_per_zone_wmark_min+0x0/0x5b returned 0 after 41 usecs > > calling kswapd_init+0x0/0x1d @ 1 > > ------------[ cut here ]------------ > > WARNING: at kernel/rcutree.c:364 rcu_enter_nohz+0x4f/0x60() > > Hardware name: System Product Name > > Modules linked in: > > Pid: 0, comm: swapper Not tainted 2.6.39-rc7-tip-03260-gb177656-dirty #126707 > > Call Trace: > > [] ? printk+0x18/0x1a > > [] warn_slowpath_common+0x6d/0xa0 > > [] ? rcu_enter_nohz+0x4f/0x60 > > [] ? rcu_enter_nohz+0x4f/0x60 > > [] warn_slowpath_null+0x1d/0x20 > > [] rcu_enter_nohz+0x4f/0x60 > > [] tick_nohz_stop_sched_tick+0x22a/0x470 > > [] cpu_idle+0x65/0xe0 > > [] rest_init+0xa1/0xa8 > > [] ? reciprocal_value+0x48/0x48 > > [] start_kernel+0x303/0x30b > > [] ? obsolete_checksetup+0x95/0x95 > > [] i386_start_kernel+0x67/0x6d > > ---[ end trace fe4ebffb2b8ff187 ]--- > > initcall kswapd_init+0x0/0x1d returned 0 after 70614 usecs > > calling extfrag_debug_init+0x0/0x78 @ 1 > > initcall extfrag_debug_init+0x0/0x78 returned 0 after 79 usecs > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/