From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933056AbcKNPOq (ORCPT ); Mon, 14 Nov 2016 10:14:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37242 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751662AbcKNPOp (ORCPT ); Mon, 14 Nov 2016 10:14:45 -0500 Date: Mon, 14 Nov 2016 16:14:48 +0100 From: Oleg Nesterov To: Mike Galbraith Cc: Peter Zijlstra , Ingo Molnar , Linus Torvalds , hartsjc@redhat.com, vbendel@redhat.com, vlovejoy@redhat.com, linux-kernel@vger.kernel.org Subject: Re: sched/autogroup: race if !sysctl_sched_autogroup_enabled ? Message-ID: <20161114151447.GA23318@redhat.com> References: <20161109165933.GA26071@redhat.com> <20161109175005.GS3142@twins.programming.kicks-ass.net> <20161110130913.GA11933@redhat.com> <20161111165743.GA29869@redhat.com> <1479045544.12006.8.camel@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1479045544.12006.8.camel@gmx.de> User-Agent: Mutt/1.5.18 (2008-05-17) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 14 Nov 2016 15:14:45 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/13, Mike Galbraith wrote: > > Autogroup never should have had knobs in the first place, and now, Oleg has > discovered that the dynamic enable/disable capability either has become, or > perhaps always was racy. It was always racy afaics, even if sysctl_sched_autogroup_enabled doesn't change. So this patch is not enough. But the main reason I dislike it is that I can't backport it ;) rhel7 runs with sysctl_sched_autogroup_enabled=0 by default, and users actually use this knob to enable it dynamically. Mike, et al, sorry for delay. I'll try to finally force myself to write the comments and the changelog and send 2 (trivial) fixes today. Oleg.