From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932121AbbJPID7 (ORCPT ); Fri, 16 Oct 2015 04:03:59 -0400 Received: from mail-lf0-f48.google.com ([209.85.215.48]:36274 "EHLO mail-lf0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751334AbbJPIDx (ORCPT ); Fri, 16 Oct 2015 04:03:53 -0400 Subject: Re: [PATCH] Fix migration of SCHED_DEADLINE tasks To: Juri Lelli , linux-kernel@vger.kernel.org References: <1444907357-13114-1-git-send-email-luca.abeni@unitn.it> <561FD6F3.4090209@arm.com> Cc: Peter Zijlstra , Ingo Molnar , Wanpeng Li From: Luca Abeni Message-ID: <5620AF64.4050208@unitn.it> Date: Fri, 16 Oct 2015 10:03:48 +0200 User-Agent: Mozilla/5.0 (X11; Linux i686; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <561FD6F3.4090209@arm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/15/2015 06:40 PM, Juri Lelli wrote: > On 15/10/15 12:09, Luca Abeni wrote: >> Commit 9d5142624256 ("sched/deadline: Reduce rq lock contention by >> eliminating locking of non-feasible target") broke select_task_rq_dl() [...] >> - dl_time_before(p->dl.deadline, >> - cpu_rq(target)->dl.earliest_dl.curr)) >> + (dl_time_before(p->dl.deadline, >> + cpu_rq(target)->dl.earliest_dl.curr) || >> + (cpu_rq(target)->dl.earliest_dl.curr == 0))) > > Can't we actually use dl.dl_nr_running here and below, so > that we won't incur any wraparound problem? Ok, I tested the patch with dl.dl_nr_running and if works for me... I am going to send the updated patch in few minutes. BTW, should we also use "dl_rq->dl_nr_running == 0" instead of "dl_rq->earliest_dl.curr == 0" in inc_dl_deadline(), and remove the comment from init_dl_rq()? If you think it is a good idea, I'll test this additional change and send a patch in next week. Thanks, Luca