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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 472A2C0650F for ; Tue, 30 Jul 2019 08:21:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 185082087F for ; Tue, 30 Jul 2019 08:21:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="nQ2b9gY6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730465AbfG3IVP (ORCPT ); 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Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hsNNd-0005P9-JV; Tue, 30 Jul 2019 08:21:09 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 598A620D27EAB; Tue, 30 Jul 2019 10:21:08 +0200 (CEST) Date: Tue, 30 Jul 2019 10:21:08 +0200 From: Peter Zijlstra To: Juri Lelli Cc: Dietmar Eggemann , Ingo Molnar , Luca Abeni , Daniel Bristot de Oliveira , Valentin Schneider , Qais Yousef , linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/5] sched/deadline: Cleanup on_dl_rq() handling Message-ID: <20190730082108.GJ31381@hirez.programming.kicks-ass.net> References: <20190726082756.5525-1-dietmar.eggemann@arm.com> <20190726082756.5525-5-dietmar.eggemann@arm.com> <20190729164932.GN31398@hirez.programming.kicks-ass.net> <20190730064115.GC8927@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190730064115.GC8927@localhost.localdomain> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 30, 2019 at 08:41:15AM +0200, Juri Lelli wrote: > On 29/07/19 18:49, Peter Zijlstra wrote: > > On Fri, Jul 26, 2019 at 09:27:55AM +0100, Dietmar Eggemann wrote: > > > Remove BUG_ON() in __enqueue_dl_entity() since there is already one in > > > enqueue_dl_entity(). > > > > > > Move the check that the dl_se is not on the dl_rq from > > > __dequeue_dl_entity() to dequeue_dl_entity() to align with the enqueue > > > side and use the on_dl_rq() helper function. > > > > > > Signed-off-by: Dietmar Eggemann > > > --- > > > kernel/sched/deadline.c | 8 +++----- > > > 1 file changed, 3 insertions(+), 5 deletions(-) > > > > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > > > index 1fa005f79307..a9cb52ceb761 100644 > > > --- a/kernel/sched/deadline.c > > > +++ b/kernel/sched/deadline.c > > > @@ -1407,8 +1407,6 @@ static void __enqueue_dl_entity(struct sched_dl_entity *dl_se) > > > struct sched_dl_entity *entry; > > > int leftmost = 1; > > > > > > - BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node)); > > > - > > > while (*link) { > > > parent = *link; > > > entry = rb_entry(parent, struct sched_dl_entity, rb_node); > > > @@ -1430,9 +1428,6 @@ static void __dequeue_dl_entity(struct sched_dl_entity *dl_se) > > > { > > > struct dl_rq *dl_rq = dl_rq_of_se(dl_se); > > > > > > - if (RB_EMPTY_NODE(&dl_se->rb_node)) > > > - return; > > > - > > > rb_erase_cached(&dl_se->rb_node, &dl_rq->root); > > > RB_CLEAR_NODE(&dl_se->rb_node); > > > > > > @@ -1466,6 +1461,9 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, > > > > > > static void dequeue_dl_entity(struct sched_dl_entity *dl_se) > > > { > > > + if (!on_dl_rq(dl_se)) > > > + return; > > > > Why allow double dequeue instead of WARN? > > As I was saying to Valentin, it can currently happen that a task could > have already been dequeued by update_curr_dl()->throttle called by > dequeue_task_dl() before calling __dequeue_task_dl(). Do you think we > should check for this condition before calling into dequeue_dl_entity()? Yes, that's what ->dl_throttled is for, right? And !->dl_throttled && !on_dl_rq() is a BUG.