Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753211AbaKLPjP (ORCPT ); Wed, 12 Nov 2014 10:39:15 -0500 Received: from casper.infradead.org ([85.118.1.10]:44796 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752736AbaKLPjO (ORCPT ); Wed, 12 Nov 2014 10:39:14 -0500 Date: Wed, 12 Nov 2014 16:39:06 +0100 From: Peter Zijlstra To: Juri Lelli Cc: Wanpeng Li , Ingo Molnar , Kirill Tkhai , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v5] sched/deadline: support dl task migration during cpu hotplug Message-ID: <20141112153906.GL29390@twins.programming.kicks-ass.net> References: <1415754413-13988-1-git-send-email-wanpeng.li@linux.intel.com> <546377FC.4090408@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <546377FC.4090408@arm.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 12, 2014 at 03:08:44PM +0000, Juri Lelli wrote: > > @@ -1185,8 +1223,9 @@ static int find_later_rq(struct task_struct *task) > > * We have to consider system topology and task affinity > > * first, then we can look for a suitable cpu. > > */ > > - cpumask_copy(later_mask, task_rq(task)->rd->span); > > - cpumask_and(later_mask, later_mask, cpu_active_mask); > > + cpumask_copy(later_mask, cpu_active_mask); > > + if (likely(task_rq(task)->online)) > > + cpumask_and(later_mask, later_mask, task_rq(task)->rd->span); > > So, here you consider the span only when the task_rq is online, > but there might be others cpus still online belonging to the same > rd->span. And you have to consider them when migrating. Actually, > migration must still be restricted to the online cpus of task's > original rd->span, or I fear you can break clustered scheduling. Ah, good point that, we must somehow find the right root domain to 'restore' the task to. Now I'm not entirely sure we still have this. Lemme ponder that. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/