Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753113AbaJ0NpR (ORCPT ); Mon, 27 Oct 2014 09:45:17 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:38570 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753001AbaJ0NpN (ORCPT ); Mon, 27 Oct 2014 09:45:13 -0400 Date: Mon, 27 Oct 2014 14:45:08 +0100 From: Peter Zijlstra To: Kirill Tkhai Cc: Tejun Heo , Burke Libbey , "linux-kernel@vger.kernel.org" , "mingo@kernel.org" Subject: Re: [PATCH] sched: reset sched_entity depth on changing parent Message-ID: <20141027134508.GI3337@twins.programming.kicks-ass.net> References: <20141024150746.GB25260@burke.local> <20141024155805.GF21513@worktop.programming.kicks-ass.net> <164441414171122@web11g.yandex.ru> <20141027120734.GA3337@twins.programming.kicks-ass.net> <20141027124002.GA4436@htj.dyndns.org> <20141027132812.GG3337@twins.programming.kicks-ass.net> <799391414416962@web4j.yandex.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <799391414416962@web4j.yandex.ru> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 27, 2014 at 04:36:02PM +0300, Kirill Tkhai wrote: > > > 27.10.2014, 16:28, "Peter Zijlstra" : > > On Mon, Oct 27, 2014 at 08:40:02AM -0400, Tejun Heo wrote: > >> ?On Mon, Oct 27, 2014 at 01:07:34PM +0100, Peter Zijlstra wrote: > >>> ?On Fri, Oct 24, 2014 at 09:18:42PM +0400, Kirill Tkhai wrote: > >>>> ?I was seeking a places where task_group of a task may change. I can't understand > >>>> ?how changing of parent's cgroup during fork() applies to a child. > >>> ?I didn't know we could change cgroup on fork(), I though the idea was > >>> ?you always inherited your parents cgroup. > >>> > >>> ?How can this be? > >> ?Hmmm? -ENEEDMORECONTEXT but the inheriting happens at one point during > >> ?fork in cgroup_post_fork(). ?The child inherits whatever the parent > >> ?cgroup is at that point. > > > > So Kirill is saying that there is a race between fork and attach such > > that a child can end up in a different cgroup than the parent and we > > need to use the cgroup_subsys::fork call to fix that up. > > I mean cgroup is the same, but sched_task_group is other (sched_task_group > is equal to parent's on the moment of dup_task_struct()). But that still means the parent changed cgroup during fork right? It started out in a different cgroup than it ended up with, and we need that .fork callback to fixup state. -- 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/