From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7467ECDE3D for ; Fri, 19 Oct 2018 20:50:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 31B292083E for ; Fri, 19 Oct 2018 20:50:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 31B292083E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=santannapisa.it Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726845AbeJTE55 (ORCPT ); Sat, 20 Oct 2018 00:57:57 -0400 Received: from mail.santannapisa.it ([193.205.80.98]:50412 "EHLO mail.santannapisa.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726321AbeJTE55 (ORCPT ); Sat, 20 Oct 2018 00:57:57 -0400 Received: from [151.40.1.127] (account l.abeni@santannapisa.it HELO nowhere) by santannapisa.it (CommuniGate Pro SMTP 6.1.11) with ESMTPSA id 133834824; Fri, 19 Oct 2018 22:50:12 +0200 Date: Fri, 19 Oct 2018 22:50:05 +0200 From: luca abeni To: Peter Zijlstra Cc: Juri Lelli , Thomas Gleixner , Juri Lelli , syzbot , Borislav Petkov , "H. Peter Anvin" , LKML , mingo@redhat.com, nstange@suse.de, syzkaller-bugs@googlegroups.com, henrik@austad.us, Tommaso Cucinotta , Claudio Scordino , Daniel Bristot de Oliveira Subject: Re: INFO: rcu detected stall in do_idle Message-ID: <20181019225005.61707c64@nowhere> In-Reply-To: <20181019113942.GH3121@hirez.programming.kicks-ass.net> References: <000000000000a4ee200578172fde@google.com> <20181016140322.GB3121@hirez.programming.kicks-ass.net> <20181016144045.GF9130@localhost.localdomain> <20181016153608.GH9130@localhost.localdomain> <20181018082838.GA21611@localhost.localdomain> <20181018122331.50ed3212@luca64> <20181018104713.GC21611@localhost.localdomain> <20181018130811.61337932@luca64> <20181019113942.GH3121@hirez.programming.kicks-ass.net> Organization: Scuola Superiore S.Anna X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 19 Oct 2018 13:39:42 +0200 Peter Zijlstra wrote: > On Thu, Oct 18, 2018 at 01:08:11PM +0200, luca abeni wrote: > > Ok, I see the issue now: the problem is that the "while > > (dl_se->runtime <= 0)" loop is executed at replenishment time, but > > the deadline should be postponed at enforcement time. > > > > I mean: in update_curr_dl() we do: > > dl_se->runtime -= scaled_delta_exec; > > if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) { > > ... > > enqueue replenishment timer at dl_next_period(dl_se) > > But dl_next_period() is based on a "wrong" deadline! > > > > > > I think that inserting a > > while (dl_se->runtime <= -pi_se->dl_runtime) { > > dl_se->deadline += pi_se->dl_period; > > dl_se->runtime += pi_se->dl_runtime; > > } > > immediately after "dl_se->runtime -= scaled_delta_exec;" would fix > > the problem, no? > > That certainly makes sense to me. Good; I'll try to work on this idea in the weekend. Thanks, Luca > The only remaining issue would then > be placing a limit on the amount of times we can take that loop; > which, as you propose in a later email; can be done separately as a > limit on runtime.