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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 C835EC28CC5 for ; Wed, 5 Jun 2019 14:20:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC5E320866 for ; Wed, 5 Jun 2019 14:20:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728384AbfFEOUI (ORCPT ); Wed, 5 Jun 2019 10:20:08 -0400 Received: from mx2.suse.de ([195.135.220.15]:37964 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727893AbfFEOUG (ORCPT ); Wed, 5 Jun 2019 10:20:06 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 18EDEAF03; Wed, 5 Jun 2019 14:20:05 +0000 (UTC) Date: Wed, 5 Jun 2019 16:20:03 +0200 From: Michal =?iso-8859-1?Q?Koutn=FD?= To: Juri Lelli Cc: peterz@infradead.org, mingo@redhat.com, rostedt@goodmis.org, lizefan@huawei.com, tj@kernel.org, bristot@redhat.com, luca.abeni@santannapisa.it, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/core: Fix cpu controller for !RT_GROUP_SCHED Message-ID: <20190605142003.GD4255@blackbody.suse.cz> References: <20190605114935.7683-1-juri.lelli@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190605114935.7683-1-juri.lelli@redhat.com> 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 Wed, Jun 05, 2019 at 01:49:35PM +0200, Juri Lelli wrote: > Existing code comes with a comment saying the "we don't support RT-tasks > being in separate groups". I'm also inclined to this check not being completely correct. This guard also prevents enabling cpu controller on unified hierarchy with !CONFIG_RT_GROUP_SCHED. (If there are any kernel RT threads in root cgroup, they can't be migrated to the newly create cpu controller's root in cgroup_update_dfl_csses().) I considered relaxing the check to non-root cgroups only, however, as your example shows, it doesn't prevent reaching the avoided state by other paths. I'm not that familiar with RT sched to tell whether RT-priority tasks in different task_groups break any assumptions. Michal