From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933862AbcBDMDl (ORCPT ); Thu, 4 Feb 2016 07:03:41 -0500 Received: from foss.arm.com ([217.140.101.70]:41124 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932475AbcBDMDh (ORCPT ); Thu, 4 Feb 2016 07:03:37 -0500 Date: Thu, 4 Feb 2016 12:04:12 +0000 From: Juri Lelli To: Steven Rostedt Cc: Peter Zijlstra , Ingo Molnar , LKML , Clark Williams , John Kacur , Daniel Bristot de Oliveira , Juri Lelli Subject: Re: [BUG] Corrupted SCHED_DEADLINE bandwidth with cpusets Message-ID: <20160204120412.GA29586@e106622-lin> References: <20160203135550.5f95ecb2@gandalf.local.home> <20160204095448.GE12132@e106622-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160204095448.GE12132@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 04/02/16 09:54, Juri Lelli wrote: > Hi Steve, > > first of all thanks a lot for your detailed report, if only all bug > reports were like this.. :) > > On 03/02/16 13:55, Steven Rostedt wrote: [...] > > Right. I think this is the same thing that happens after hotplug. IIRC > the code paths are actually the same. The problem is that hotplug or > cpuset reconfiguration operations are destructive w.r.t. root_domains, > so we lose bandwidth information when that happens. The problem is that > we only store cumulative information regarding bandwidth in root_domain, > while information about which task belongs to which cpuset is store in > cpuset data structures. > > I tried to fix this a while back, but my tentative was broken, I failed > to get locking right and, even though it seemed to fix the issue for me, > it was prone to race conditions. You might still want to have a look at > that for reference: https://lkml.org/lkml/2015/9/2/162 > [...] > > It's good that we can recover, but that's still a bug yes :/. > > I'll try to see if my broken patch make what you are seeing apparently > disappear, so that we can at least confirm that we are seeing the same > problem; you could do the same if you want, I pushed that here > No it doesn't solve this :/. I placed restoring code in the hotplug workfn, so updates generated by toggling sched_load_balance don't get caught, of course. But, this at least tells us that we should solve this someplace else. Best, - Juri