Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756828AbaFZLIW (ORCPT ); Thu, 26 Jun 2014 07:08:22 -0400 Received: from e28smtp05.in.ibm.com ([122.248.162.5]:59256 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754661AbaFZLIU (ORCPT ); Thu, 26 Jun 2014 07:08:20 -0400 Date: Thu, 26 Jun 2014 16:38:11 +0530 From: Srikar Dronamraju To: Kirill Tkhai Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , tkhai@yandex.ru, Mike Galbraith , khorenko@parallels.com, Ben Segall , Paul Turner Subject: Re: [PATCH v2 1/3] sched/fair: Disable runtime_enabled on dying rq Message-ID: <20140626110811.GA20048@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20140624074148.8738.57690.stgit@tkhai> <1403596432.3462.26.camel@tkhai> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1403596432.3462.26.camel@tkhai> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14062611-8256-0000-0000-00000E0B0FA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Kirill Tkhai [2014-06-24 11:53:52]: > We kill rq->rd on the CPU_DOWN_PREPARE stage: > > cpuset_cpu_inactive -> cpuset_update_active_cpus -> partition_sched_domains -> > -> cpu_attach_domain -> rq_attach_root -> set_rq_offline > > This unthrottles all throttled cfs_rqs. > > But the cpu is still able to call schedule() till > > take_cpu_down->__cpu_disable() > > is called from stop_machine. > > This case the tasks from just unthrottled cfs_rqs are pickable > in a standard scheduler way, and they are picked by dying cpu. > The cfs_rqs becomes throttled again, and migrate_tasks() > in migration_call skips their tasks (one more unthrottle > in migrate_tasks()->CPU_DYING does not happen, because rq->rd > is already NULL). > > Patch sets runtime_enabled to zero. This guarantees, the runtime > is not accounted, and the cfs_rqs won't exceed given > cfs_rq->runtime_remaining = 1, and tasks will be pickable > in migrate_tasks(). runtime_enabled is recalculated again > when rq becomes online again. > > Ben Segall also noticed, we always enable runtime in > tg_set_cfs_bandwidth(). Actually, we should do that for online > cpus only. To fix that, we check if a cpu is online when > its rq is locked. This guarantees we do not have races with > set_rq_offline(), which also requires rq->lock. > > v2: Fix race with tg_set_cfs_bandwidth(). > Move cfs_rq->runtime_enabled=0 above unthrottle_cfs_rq(). > > Signed-off-by: Kirill Tkhai > CC: Konstantin Khorenko > CC: Ben Segall > CC: Paul Turner > CC: Srikar Dronamraju > CC: Mike Galbraith > CC: Peter Zijlstra > CC: Ingo Molnar looks good to me. Reviewed-by: Srikar Dronamraju -- Thanks and Regards Srikar Dronamraju -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/