From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753679AbcHPPaH (ORCPT ); Tue, 16 Aug 2016 11:30:07 -0400 Received: from merlin.infradead.org ([205.233.59.134]:59090 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750864AbcHPPaG (ORCPT ); Tue, 16 Aug 2016 11:30:06 -0400 Date: Tue, 16 Aug 2016 17:29:49 +0200 From: Peter Zijlstra To: Tejun Heo Cc: Heiko Carstens , Ming Lei , Thomas Gleixner , LKML , Yasuaki Ishimatsu , Andrew Morton , Lai Jiangshan , Michael Holzheu , Martin Schwidefsky Subject: Re: [bisected] "sched: Allow per-cpu kernel threads to run on online && !active" causes warning Message-ID: <20160816152949.GL30192@twins.programming.kicks-ass.net> References: <20160727125412.GB3912@osiris> <20160730112552.GA3744@osiris> <20160815111908.GA3903@osiris> <20160815224801.GA3672@mtj.duckdns.org> <20160816075505.GB3896@osiris> <20160816152027.GD9516@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160816152027.GD9516@htj.duckdns.org> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 16, 2016 at 11:20:27AM -0400, Tejun Heo wrote: > As long as the mapping doesn't change after the first onlining of the > CPU, the workqueue side shouldn't be too difficult to fix up. I'll > look into it. For memory allocations, as long as the cpu <-> node > mapping is established before any memory allocation for the cpu takes > place, it should be fine too, I think. Don't we allocate per-cpu memory for 'cpu_possible_map' on boot? There's a whole bunch of per-cpu memory users that does things like: for_each_possible_cpu(cpu) { struct foo *foo = per_cpu_ptr(&per_cpu_var, cpu); /* muck with foo */ } Which requires a cpu->node map for all possible cpus at boot time.