From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752814Ab2J1OFv (ORCPT ); Sun, 28 Oct 2012 10:05:51 -0400 Received: from mail-ee0-f46.google.com ([74.125.83.46]:64367 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751528Ab2J1OFt (ORCPT ); Sun, 28 Oct 2012 10:05:49 -0400 Date: Sun, 28 Oct 2012 15:05:44 +0100 From: Ingo Molnar To: Mike Galbraith Cc: Xiaotian Feng , Peter Zijlstra , linux-kernel@vger.kernel.org, Xiaotian Feng , Ingo Molnar Subject: Re: [PATCH] sched, autogroup: fix crash on reboot when autogroup is disabled Message-ID: <20121028140544.GA28216@gmail.com> References: <1350635770-9189-1-git-send-email-xtfeng@gmail.com> <1350654126.2768.5.camel@twins> <1350736696.5123.24.camel@maggy.simpson.net> <1351283371.16639.111.camel@maggy.simpson.net> <1351362370.4503.3.camel@maggy.simpson.net> <20121028102520.GA7711@gmail.com> <1351430004.8685.17.camel@maggy.simpson.net> <20121028131950.GA15159@gmail.com> <1351431201.8685.22.camel@maggy.simpson.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1351431201.8685.22.camel@maggy.simpson.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Mike Galbraith wrote: > On Sun, 2012-10-28 at 14:19 +0100, Ingo Molnar wrote: > > * Mike Galbraith wrote: > > > > > On Sun, 2012-10-28 at 11:25 +0100, Ingo Molnar wrote: > > > > * Mike Galbraith wrote: > > > > > > > > > > > > No knobs, no glitz, nada, just a cute little thing folks can turn > > > > > on if they don't want to muck about with cgroups and/or systemd. > > > > > > > > Please also keep the Kconfig switch and reuse it to turn on > > > > the 'autogroups' knob. > > > > > > > > That way people with existing .config's don't have to change > > > > a thing to get this functionality. > > > > > > The Kconfig option is still there. The noautogroup -> > > > autogroup arg change just makes it off by default (since an > > > on/off switch would have to be a full move everybody thing > > > post 8323f26ce race fix), so distros can make it available in > > > their swiss army knife config, but it'll be out of the way > > > unless specifically asked for by the user at boot. > > > > > > I can make it default 'on' by removing that arg change if you > > > think that's the better way to go, but opt in at boot sounded > > > better to me given there is no runtime on/off switch at all > > > now. > > > > If I got your patch right then adding a command line option to > > turn it on will disable it in essence for pretty much everyone > > who has CONFIG_SCHED_AUTOGROUP=y in their .config today. > > With no user intervention, yes. 'No user intervention' is what happens with new kernel commandline options, in 99.9999% of the cases. > > The patch should not change the defaults for existing > > .config's. > > > > I.e. if autogroups was off, it should stay off, but if > > autogroups was enabled in the .config and the kernel booted > > with it enabled, then it should continue to do so in the > > future as well. > > > > Adding a boot tweak and removing the runtime knobs is OK - > > changing the current default functionality is not. > > Ok, I'll whack the arg change and respin. Thanks! I'd also suggest to still expose the state of autosched in /proc/sys, read-only, so that its status can be checked. Ingo