From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751404Ab1AEPSL (ORCPT ); Wed, 5 Jan 2011 10:18:11 -0500 Received: from casper.infradead.org ([85.118.1.10]:37104 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751231Ab1AEPSJ convert rfc822-to-8bit (ORCPT ); Wed, 5 Jan 2011 10:18:09 -0500 Subject: Re: cgroup scheduling: Adding kthreadd to a non-RT cgroup can deadlock the kernel From: Peter Zijlstra To: Nelson Elhage Cc: Paul Menage , Li Zefan , linux-kernel@vger.kernel.org In-Reply-To: References: <20110105045447.GN23414@ksplice.com> <1294220650.2016.197.camel@laptop> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Wed, 05 Jan 2011 16:18:30 +0100 Message-ID: <1294240710.2016.264.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2011-01-05 at 10:02 -0500, Nelson Elhage wrote: > Ok. I bothered reporting this here since the kernel /does/ try to prevent you > from shooting yourself in the foot in related ways, by moving existing > SCHED_FIFO tasks into a cgroup without any RT runtime, so I figured it might > make sense to add a check here. libcgroup, for example, will try to move all > processes into a default cgroup, ignoring errors, and relies on the kernel to > prevent it from shooting itself in the foot. > > It sounds like you consider that behavior a bug, though, so I'll go report this > bug there. Right, so we try to catch obvious cases, but its near impossible to catch all cases. And its not only the scheduler controller, I bet you can get into trouble with some of the other controllers as well.