Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S971287AbdDUJrU (ORCPT ); Fri, 21 Apr 2017 05:47:20 -0400 Received: from foss.arm.com ([217.140.101.70]:35142 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S971223AbdDUJrS (ORCPT ); Fri, 21 Apr 2017 05:47:18 -0400 Date: Fri, 21 Apr 2017 10:47:29 +0100 From: Juri Lelli To: luca abeni Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Claudio Scordino , Steven Rostedt , Tommaso Cucinotta , Daniel Bristot de Oliveira , Mathieu Poirier Subject: Re: [PATCH] sched/deadline: fix switching to -deadline Message-ID: <20170421094729.GR23862@e106622-lin> References: <1492716656-5362-1-git-send-email-luca.abeni@santannapisa.it> <20170421093926.GQ23862@e106622-lin> <20170421114240.0ef43522@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170421114240.0ef43522@nowhere> 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 Content-Length: 2042 Lines: 49 On 21/04/17 11:42, Luca Abeni wrote: > On Fri, 21 Apr 2017 10:39:26 +0100 > Juri Lelli wrote: > > > Hi Luca, > > > > On 20/04/17 21:30, Luca Abeni wrote: > > > From: Luca Abeni > > > > > > When switching to -deadline, if the scheduling deadline of a task is > > > in the past then switched_to_dl() calls setup_new_entity() to > > > properly initialize the scheduling deadline and runtime. > > > > > > The problem is that the task is enqueued _before_ having its > > > parameters initialized by setup_new_entity(), and this can cause > > > problems. For example, a task with its out-of-date deadline in the > > > past will potentially be enqueued as the highest priority one; > > > however, its adjusted deadline may not be the earliest one. > > > > > > This patch fixes the problem by initializing the task's parameters > > > before enqueuing it. > > > > > > Signed-off-by: Luca Abeni > > > Reviewed-by: Daniel Bristot de Oliveira > > > --- > > > kernel/sched/deadline.c | 12 ++++-------- > > > 1 file changed, 4 insertions(+), 8 deletions(-) > > > > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > > > index a2ce590..ec53d24 100644 > > > --- a/kernel/sched/deadline.c > > > +++ b/kernel/sched/deadline.c > > > @@ -950,6 +950,10 @@ enqueue_dl_entity(struct sched_dl_entity > > > *dl_se, update_dl_entity(dl_se, pi_se); > > > else if (flags & ENQUEUE_REPLENISH) > > > replenish_dl_entity(dl_se, pi_se); > > > + else if ((flags & ENQUEUE_RESTORE) && > > > > Not sure I understand how this works. AFAICT we are doing > > __sched_setscheduler() when we want to catch the case of a new > > dl_entity (SCHED_{OTHER,FIFO} -> SCHED_DEADLINE}, but queue_flags > > (which are passed to enqueue_task()) don't seem to have > > ENQUEUE_RESTORE set? > > I was under the impression sched_setscheduler() sets ENQUEUE_RESTORE... > Oh, I think it works "by coincidence", as ENQUEUE_RESTORE == DEQUEUE_SAVE == 0x02 ? :)