From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752485AbcBKMMM (ORCPT ); Thu, 11 Feb 2016 07:12:12 -0500 Received: from foss.arm.com ([217.140.101.70]:53632 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751366AbcBKMMK (ORCPT ); Thu, 11 Feb 2016 07:12:10 -0500 Date: Thu, 11 Feb 2016 12:12:57 +0000 From: Juri Lelli To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, mingo@redhat.com, luca.abeni@unitn.it, vincent.guittot@linaro.org, wanpeng.li@hotmail.com Subject: Re: [PATCH 1/2] sched/deadline: add per rq tracking of admitted bandwidth Message-ID: <20160211121257.GL11415@e106622-lin> References: <1454935531-7541-1-git-send-email-juri.lelli@arm.com> <1454935531-7541-2-git-send-email-juri.lelli@arm.com> <20160210113258.GX11415@e106622-lin> <20160210093702.10c655be@gandalf.local.home> <20160210162748.GI11415@e106622-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160210162748.GI11415@e106622-lin> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/02/16 16:27, Juri Lelli wrote: > On 10/02/16 09:37, Steven Rostedt wrote: > > On Wed, 10 Feb 2016 11:32:58 +0000 > > Juri Lelli wrote: > > [...] > > > > I applied this patch and patch 2 and hit this: > > [...] > > > > It's the warning you added in __dl_sub_ac(). > > > > OK. There are still holes where we fail to properly update per-rq bw. It > seems (by running you test) that we fail to move the per-rq bw when we > move the root_domain bw due css_set_move_task(). So, the final > task_dead_dl() tries to remove bw from where there isn't. > > I'm trying to see how we can close this hole. > So, just to give an update from yesterday (kind of tricky this one :/). I think we still have (at least) two problems: - select_task_rq_dl, if we select a different target - select_task_rq might make use of select_fallback_rq, if cpus_allowed changed after the task went to sleep Second case is what creates the problem here, as we don't update task_rq(p) and fallback_cpu ac_bw. I was thinking we might do so, maybe adding fallback_cpu in task_struct, from migrate_task_rq_dl() (it has to be added yes), but I fear that we should hold both rq locks :/. Luca, did you already face this problem (if I got it right) and thought of a way to fix it? I'll go back and stare a bit more at those paths. Best, - Juri