From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753586AbbAWEDJ (ORCPT ); Thu, 22 Jan 2015 23:03:09 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:31157 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753073AbbAWEDH (ORCPT ); Thu, 22 Jan 2015 23:03:07 -0500 Message-ID: <54C1C7D2.906@oracle.com> Date: Thu, 22 Jan 2015 23:02:26 -0500 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Lai Jiangshan , Ingo Molnar , Peter Zijlstra , LKML , "davej@codemonkey.org.uk >> Dave Jones" Subject: Re: rcu, sched: WARNING: CPU: 30 PID: 23771 at kernel/rcu/tree_plugin.h:337 rcu_read_unlock_special+0x369/0x550() References: <54BBC084.2030604@oracle.com> <20150118232255.GD9719@linux.vnet.ibm.com> <54BE76B9.7070907@oracle.com> <20150121025754.GV9719@linux.vnet.ibm.com> <54BFC979.8040107@oracle.com> <20150122004305.GJ9719@linux.vnet.ibm.com> <54C1BFFD.9060707@oracle.com> <20150123035158.GP9719@linux.vnet.ibm.com> In-Reply-To: <20150123035158.GP9719@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/22/2015 10:51 PM, Paul E. McKenney wrote: > On Thu, Jan 22, 2015 at 10:29:01PM -0500, Sasha Levin wrote: >> > On 01/21/2015 07:43 PM, Paul E. McKenney wrote: >>> > > On Wed, Jan 21, 2015 at 10:44:57AM -0500, Sasha Levin wrote: >>>> > >> On 01/20/2015 09:57 PM, Paul E. McKenney wrote: >>>>>>> > >>>>> So RCU believes that an RCU read-side critical section that ended within >>>>>>>>> > >>>>>>> an interrupt handler (in this case, an hrtimer) somehow got preempted. >>>>>>>>> > >>>>>>> Which is not supposed to happen. >>>>>>>>> > >>>>>>> >>>>>>>>> > >>>>>>> Do you have CONFIG_PROVE_RCU enabled? If not, could you please enable it >>>>>>>>> > >>>>>>> and retry? >>>>>>> > >>>>> >>>>>>> > >>>>> I did have CONFIG_PROVE_RCU, and didn't see anything else besides what I pasted here. >>>>> > >>> OK, fair enough. I do have a stack of RCU CPU stall-warning changes on >>>>> > >>> their way in, please see v3.19-rc1..630181c4a915 in -rcu, which is at: >>>>> > >>> >>>>> > >>> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git >>>>> > >>> >>>>> > >>> These handle the problems that Dave Jones, yourself, and a few others >>>>> > >>> located this past December. Could you please give them a spin? >>>> > >> >>>> > >> They seem to be a part of -next already, so this testing already includes them. >>>> > >> >>>> > >> I seem to be getting them about once a day, anything I can add to debug it? >>> > > >>> > > Could you please try reproducing with the following patch? >> > >> > Yes, and I've got mixed results. It reproduced, and all I got was: >> > >> > [ 717.645572] =============================== >> > [ 717.645572] [ INFO: suspicious RCU usage. ] >> > [ 717.645572] 3.19.0-rc5-next-20150121-sasha-00064-g3c37e35-dirty #1809 Tainted: G W >> > [ 717.645572] ------------------------------- >> > [ 717.645572] kernel/rcu/tree_plugin.h:337 rcu_read_unlock() from irq or softirq with blocking in critical section!!! >> > [ 717.645572] ! >> > [ 717.645572] >> > [ 717.645572] other info that might help us debug this: >> > [ 717.645572] >> > [ 717.645572] >> > [ 717.645572] rcu_scheduler_active = 1, debug_locks = 1 >> > [ 717.645572] 3 locks held by trinity-c29/16497: >> > [ 717.645572] #0: (&sb->s_type->i_mutex_key){+.+.+.}, at: [] lookup_slow+0xd3/0x420 >> > [ 717.645572] #1: >> > [hang] >> > >> > So the rest of the locks/stack trace didn't get printed, nor the pr_alert() which >> > should follow that. >> > >> > I've removed the lockdep call and will re-run it. > Thank you! You are keeping the pr_alert(), correct? Yup, just the lockdep call goes away. Thanks, Sasha