From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753972AbZBWJ2T (ORCPT ); Mon, 23 Feb 2009 04:28:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752302AbZBWJ2D (ORCPT ); Mon, 23 Feb 2009 04:28:03 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:60620 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752011AbZBWJ2B (ORCPT ); Mon, 23 Feb 2009 04:28:01 -0500 Date: Mon, 23 Feb 2009 10:27:44 +0100 From: Ingo Molnar To: Andrew Morton Cc: "Paul E. McKenney" , Vegard Nossum , stable@kernel.org, Nick Piggin , Pekka Enberg , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: fix lazy vmap purging (use-after-free error) Message-ID: <20090223092744.GL9582@elte.hu> References: <19f34abd0902201551o65a3650egf29d81e8b6823d67@mail.gmail.com> <20090221014056.GU6960@linux.vnet.ibm.com> <19f34abd0902210130p62fba6d0n906b321949409578@mail.gmail.com> <20090221174703.GA6860@linux.vnet.ibm.com> <19f34abd0902211008k39afd449k604aaf34f693c9a6@mail.gmail.com> <19f34abd0902211037w2293af16t561444d11cc834b8@mail.gmail.com> <20090222030030.GD6860@linux.vnet.ibm.com> <20090223051709.GA5990@linux.vnet.ibm.com> <20090223090735.GH9582@elte.hu> <20090223011712.853aa94d.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090223011712.853aa94d.akpm@linux-foundation.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean 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=3.2.3 -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 * Andrew Morton wrote: > On Mon, 23 Feb 2009 10:07:35 +0100 Ingo Molnar wrote: > > > > --- > > > > > > init/main.c | 3 +++ > > > kernel/rcuclassic.c | 4 +++- > > > kernel/rcutree.c | 4 +++- > > > 3 files changed, 9 insertions(+), 2 deletions(-) > > > > > > diff --git a/init/main.c b/init/main.c > > > index 8442094..51f4b71 100644 > > > --- a/init/main.c > > > +++ b/init/main.c > > > @@ -121,6 +121,8 @@ static char *static_command_line; > > > static char *execute_command; > > > static char *ramdisk_execute_command; > > > > > > +int idle_task_is_really_idle; /* set to 1 late in boot. */ > > > + > > > #ifdef CONFIG_SMP > > > /* Setup configured maximum number of CPUs to activate */ > > > unsigned int __initdata setup_max_cpus = NR_CPUS; > > > @@ -463,6 +465,7 @@ static noinline void __init_refok rest_init(void) > > > * at least once to get things moving: > > > */ > > > init_idle_bootup_task(current); > > > + idle_task_is_really_idle = 1; > > > preempt_enable_no_resched(); > > > schedule(); > > > preempt_disable(); > > > > Could you please use system_state instead? We could insert a new > > stage - or just use SYSTEM_RUNNING as the trigger. > > I think the standalone flag is better (once those > extern-decls-in-C get fixed). > > system_state's semantics have, err, evolved over time. If > this happens again (and the patch sneaks past my attention) > then there's a risk that code which depends upon system_state > will break - this has happened in the past. Plus piling more > dependencies on system_state of course makes any evolution of > its semantics harder to do... All we need is a SYSTEM_BOOTING_EARLY boundary - prior which there's no real scheduling yet. I used SYSTEM_SCHEDULER_BOOTING state before and it worked well and wasnt fragile. Our system_state semantics problems were more rooted in the fact that the SYSTEM_BOOTING stage wasnt well defined. But if we did a SYSTEM_SCHEDULER_BOOTING stage that would be pretty bit-rot-safe. Ingo