From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751599AbdG0SPz (ORCPT ); Thu, 27 Jul 2017 14:15:55 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:59722 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751522AbdG0SPy (ORCPT ); Thu, 27 Jul 2017 14:15:54 -0400 To: Tejun Heo , Lai Jiangshan , linux-kernel@vger.kernel.org Cc: nfont@linux.vnet.ibm.com, Michael Bringmann From: Michael Bringmann Subject: [PATCH v6] workqueue: Fix edge cases for calc of pool's cpumask Organization: IBM Linux Technology Center Date: Thu, 27 Jul 2017 13:15:48 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 17072718-8235-0000-0000-00000C02B7C7 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007436; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00893743; UDB=6.00446844; IPR=6.00673902; 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 18:15:51 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17072718-8236-0000-0000-00003CF438E6 Message-Id: <5c421712-fb38-3020-d3fc-b9bdea792cd3@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-1707270285 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > " + "possible intersect\n"); + return false; + } + return !cpumask_equal(cpumask, attrs->cpumask); use_dfl: