From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754014AbbAWDwJ (ORCPT ); Thu, 22 Jan 2015 22:52:09 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:58546 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752275AbbAWDwF (ORCPT ); Thu, 22 Jan 2015 22:52:05 -0500 Date: Thu, 22 Jan 2015 19:51:58 -0800 From: "Paul E. McKenney" To: Sasha Levin 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() Message-ID: <20150123035158.GP9719@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54C1BFFD.9060707@oracle.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15012303-0033-0000-0000-0000036E72ED Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Thanx, Paul