From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751625AbdG0SmV (ORCPT ); Thu, 27 Jul 2017 14:42:21 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:37531 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751461AbdG0SmU (ORCPT ); Thu, 27 Jul 2017 14:42:20 -0400 Subject: Re: [PATCH v6] workqueue: Fix edge cases for calc of pool's cpumask To: Michael Bringmann , Tejun Heo , Lai Jiangshan , linux-kernel@vger.kernel.org References: <5c421712-fb38-3020-d3fc-b9bdea792cd3@linux.vnet.ibm.com> From: Nathan Fontenot Date: Thu, 27 Jul 2017 13:42:16 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <5c421712-fb38-3020-d3fc-b9bdea792cd3@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 17072718-0020-0000-0000-00000C73C07B X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007436; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00893751; UDB=6.00446849; IPR=6.00673911; BA=6.00005495; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016411; XFM=3.00000015; UTC=2017-07-27 18:42:18 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17072718-0021-0000-0000-00005D731514 Message-Id: <47ac4fb9-a316-0125-7d4e-73cf602d891e@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-27_10:,, 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=8.0.1-1706020000 definitions=main-1707270291 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/27/2017 01:15 PM, Michael Bringmann wrote: > > On NUMA systems with dynamic processors, the content of the cpumask > may change over time. As new processors are added via DLPAR operations, > workqueues are created for them. Depending upon the order in which CPUs > are added/removed, we may run into problems with the content of the > cpumask used by the workqueues. This patch deals with situations where > the online cpumask for a node is a proper superset of possible cpumask > for the node. It also deals with edge cases where the order in which > CPUs are removed/added from the online cpumask may leave the set for a > node empty, and require execution by CPUs on another node. > > In these and other cases, the patch attempts to ensure that a valid, > usable cpumask is used to set up newly created pools for workqueues. > This patch provides a fix for NUMA systems which can add/subtract > processors dynamically. The patch is expected to be an intermediate > one while developers search for any underlying issues. > > [With additions to the patch provided by Tejun Hao ] > > Signed-off-by: Michael Bringmann > --- > Changes in V6: > -- Update descriptive text > --- > kernel/workqueue.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index c74bf39..6b6d540 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -3577,6 +3577,13 @@ static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node, > > /* yeap, return possible CPUs in @node that @attrs wants */ > cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]); > + > + if (cpumask_empty(cpumask)) { > + pr_warn_once("WARNING: workqueue cpumask: onl intersect > " ^^^ This message doesn't seem right, or I am missing something, "onl"? -Nathan > + "possible intersect\n"); > + return false; > + } > + > return !cpumask_equal(cpumask, attrs->cpumask); > > use_dfl: >