From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932766AbZIDHib (ORCPT ); Fri, 4 Sep 2009 03:38:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751585AbZIDHia (ORCPT ); Fri, 4 Sep 2009 03:38:30 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:45795 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750760AbZIDHia (ORCPT ); Fri, 4 Sep 2009 03:38:30 -0400 Date: Fri, 4 Sep 2009 09:37:49 +0200 From: Ingo Molnar To: Oleg Nesterov Cc: "Eric W. Biederman" , arjan@infradead.org, jeremy@goop.org, mschmidt@redhat.com, mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, tj@kernel.org, tglx@linutronix.de, Linus Torvalds , Andrew Morton , linux-tip-commits@vger.kernel.org, Rusty Russell Subject: Re: [PATCH 0/1] kthreads: simplify !kthreadd_task logic, kill kthreadd_task_init_done Message-ID: <20090904073749.GB20598@elte.hu> References: <20090901100351.GA3361@elte.hu> <20090901113914.GA23578@elte.hu> <20090901130436.GA22514@redhat.com> <20090901131440.GA29783@elte.hu> <20090901133709.GA24041@redhat.com> <20090901135925.GA9083@elte.hu> <20090901145526.GA31317@redhat.com> <20090901165235.GA9105@redhat.com> <20090902091340.GA5173@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090902091340.GA5173@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Oleg Nesterov wrote: > On 09/01, Eric W. Biederman wrote: > > > > Oleg Nesterov writes: > > > > > On 09/01, Oleg Nesterov wrote: > > >> > > >> On 09/01, Ingo Molnar wrote: > > >> > > > >> > * Oleg Nesterov wrote: > > >> > > > >> > > On 09/01, Ingo Molnar wrote: > > >> > > > > > >> > > > * Oleg Nesterov wrote: > > >> > > > > > >> > > > > Yes, this should work. But I _think_ we can make the better fix... > > >> > > > > > > >> > > > > I'll try to make the patch soon. Afaics we don't need > > >> > > > > kthreadd_task_init_done. > > >> > > > > > >> > > > ok. > > >> > > > > >> > > Just in case, the patch is ready. [...] > > >> > > > >> > yes - that's roughly the cleanup i referred to in the commit log. > > >> > > > >> > way too late for -rc8 though - the minimal fix i did _might_ be > > >> > eligible. > > >> > > > >> > agreed? > > >> > > >> Agreed. Then I will sent the patch on top of this change. > > > > > > OK, I am sending the patch on top of your fix. Not sure how to really > > > test it, but at least the kernel works when I apply the debugging patch > > > below on top. > > > > Stupid question. How is it that we wind up trying to start kernel threads > > before it is safe to do so? > > > > Races should be impossible because the scheduler isn't running until a few > > lines later. > > Yes, I am confused too. > > At first I thought I understand the race, now I don't. Please see > the whole thread: http://marc.info/?t=125180592500005 I dont understand it either - and the .config being !SMP excludes any sort of SMP race as well. Lets delay this until i can debug it more fully. Ingo