From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753874AbdDKVcR (ORCPT ); Tue, 11 Apr 2017 17:32:17 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:42487 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753419AbdDKVcN (ORCPT ); Tue, 11 Apr 2017 17:32:13 -0400 Date: Tue, 11 Apr 2017 14:32:08 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: linux-kernel@vger.kernel.org Subject: Re: There is a Tasks RCU stall warning Reply-To: paulmck@linux.vnet.ibm.com References: <20170411211802.GA19165@linux.vnet.ibm.com> <20170411172107.59030e32@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170411172107.59030e32@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17041121-2213-0000-0000-0000018C71A3 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006919; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000208; SDB=6.00846205; UDB=6.00417366; IPR=6.00624638; BA=6.00005284; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015010; XFM=3.00000013; UTC=2017-04-11 21:32:11 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17041121-2214-0000-0000-000055685757 Message-Id: <20170411213208.GG1600@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-04-11_16:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1702020001 definitions=main-1704110165 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 11, 2017 at 05:21:07PM -0400, Steven Rostedt wrote: > On Tue, 11 Apr 2017 14:18:02 -0700 > "Paul E. McKenney" wrote: > > > Hello, Steve, > > > > Network connectivity issues... :-/ > > ug > > > There is already a Tasks RCU stall warning, but it waits for > > ten -minutes- before complaining. You can change this with the > > rcupdate.rcu_task_stall_timeout kernel boot parameter, if you wish. > > > > Or did you wait longer than ten minutes? > > Hmm, I may have waited longer. But I can try again and shorten the > timeout. Failing that, you might try carefully placed printk() calls in rcu_tasks_kthread(). The loop spinning on non-empty rcu_tasks_holdouts() should loop at most once per second, so you can get away with quite a bit of instrumentation. Unlike much of the rest of RCU. ;-) Thanx, Paul