From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752347AbcG3L0I (ORCPT ); Sat, 30 Jul 2016 07:26:08 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:14601 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750919AbcG3L0A (ORCPT ); Sat, 30 Jul 2016 07:26:00 -0400 X-IBM-Helo: d06dlp03.portsmouth.uk.ibm.com X-IBM-MailFrom: heiko.carstens@de.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Sat, 30 Jul 2016 13:25:52 +0200 From: Heiko Carstens To: Thomas Gleixner Cc: Peter Zijlstra , LKML , Tejun Heo Subject: Re: [bisected] "sched: Allow per-cpu kernel threads to run on online && !active" causes warning References: <20160727125412.GB3912@osiris> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16073011-0020-0000-0000-000001DFB9E2 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16073011-0021-0000-0000-00001CEFF090 Message-Id: <20160730112552.GA3744@osiris> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-07-30_09:,, 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=8.0.1-1604210000 definitions=main-1607300122 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 27, 2016 at 05:23:05PM +0200, Thomas Gleixner wrote: > On Wed, 27 Jul 2016, Heiko Carstens wrote: > > [ 3.162961] ([<0000000000176c30>] select_task_rq+0xc0/0x1a8) > > [ 3.162963] ([<0000000000177d64>] try_to_wake_up+0x2e4/0x478) > > [ 3.162968] ([<000000000015d46c>] create_worker+0x174/0x1c0) > > [ 3.162971] ([<0000000000161a98>] alloc_unbound_pwq+0x360/0x438) > > > For some unknown reason select_task_rq() gets called with a task that has > > nr_cpus_allowed == 0. Hence "cpu = cpumask_any(tsk_cpus_allowed(p));" > > within select_task_rq() will set cpu to nr_cpu_ids which in turn causes the > > warning later on. > > > > It only happens with more than one node, otherwise it seems to work fine. > > > > Any idea what could be wrong here? > > create_worker() > tsk = kthread_create_on_node(); > kthread_bind_mask(tsk, pool->attrs->cpumask); > do_set_cpus_allowed(tsk, mask); > set_cpus_allowed_common(tsk, mask); > cpumask_copy(&tsk->cpus_allowed, mask); > tsk->nr_cpus_allowed = cpumask_weight(mask); > wake_up_process(task); > > So this looks like pool->attrs->cpumask is simply empty..... Just had some time to look into this a bit more. Looks like we initialize the cpu_to_node_masks (way) too late on s390 for fake numa. So Peter's patch just revealed that problem. I'll see if initializing the masks earlier will fix this, but I think it will.