From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754525AbcFPTjL (ORCPT ); Thu, 16 Jun 2016 15:39:11 -0400 Received: from mail-yw0-f196.google.com ([209.85.161.196]:34222 "EHLO mail-yw0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754467AbcFPTjI (ORCPT ); Thu, 16 Jun 2016 15:39:08 -0400 Date: Thu, 16 Jun 2016 15:39:05 -0400 From: Tejun Heo To: Peter Zijlstra Cc: Michael Ellerman , Gautham R Shenoy , Thomas Gleixner , Abdul Haleem , Aneesh Kumar , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] workqueue:Fix affinity of an unbound worker of a node with 1 online CPU Message-ID: <20160616193905.GC3262@mtj.duckdns.org> References: <20160614112234.GF30154@twins.programming.kicks-ass.net> <20160615101936.GA31671@in.ibm.com> <20160615113249.GH30909@twins.programming.kicks-ass.net> <20160615125033.GB31671@in.ibm.com> <20160615131415.GI30909@twins.programming.kicks-ass.net> <20160615160112.GC24102@mtj.duckdns.org> <1466079084.19127.2.camel@ellerman.id.au> <20160616124548.GE30921@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160616124548.GE30921@twins.programming.kicks-ass.net> User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 16, 2016 at 02:45:48PM +0200, Peter Zijlstra wrote: > Subject: workqueue: Fix setting affinity of unbound worker threads > From: Peter Zijlstra > Date: Thu Jun 16 14:38:42 CEST 2016 > > With commit e9d867a67fd03ccc ("sched: Allow per-cpu kernel threads to > run on online && !active"), __set_cpus_allowed_ptr() expects that only > strict per-cpu kernel threads can have affinity to an online CPU which > is not yet active. > > This assumption is currently broken in the CPU_ONLINE notification > handler for the workqueues where restore_unbound_workers_cpumask() > calls set_cpus_allowed_ptr() when the first cpu in the unbound > worker's pool->attr->cpumask comes online. Since > set_cpus_allowed_ptr() is called with pool->attr->cpumask in which > only one CPU is online which is not yet active, we get the following > WARN_ON during an CPU online operation. Applied to wq/for-4.7-fixes. Thanks. -- tejun