From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758535AbZBTRZi (ORCPT ); Fri, 20 Feb 2009 12:25:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754853AbZBTRZ3 (ORCPT ); Fri, 20 Feb 2009 12:25:29 -0500 Received: from e1.ny.us.ibm.com ([32.97.182.141]:35212 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754562AbZBTRZ2 (ORCPT ); Fri, 20 Feb 2009 12:25:28 -0500 Date: Fri, 20 Feb 2009 09:25:26 -0800 From: "Paul E. McKenney" To: Ingo Molnar Cc: Vegard Nossum , stable@kernel.org, Andrew Morton , Nick Piggin , Pekka Enberg , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: fix lazy vmap purging (use-after-free error) Message-ID: <20090220172526.GM6960@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20090220134121.GA19575@damson.getinternet.no> <20090220135000.GA9616@elte.hu> <20090220140157.GA12799@elte.hu> <19f34abd0902200651k7e86aebay5398ef5ac0578561@mail.gmail.com> <20090220154619.GC6960@linux.vnet.ibm.com> <20090220160409.GB11294@elte.hu> <20090220164441.GG6960@linux.vnet.ibm.com> <20090220171427.GE24538@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090220171427.GE24538@elte.hu> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 20, 2009 at 06:14:27PM +0100, Ingo Molnar wrote: > > * Paul E. McKenney wrote: > > > > > So, what flavor of RCU were you using? > > > > > > well, even in preemptible RCU the grace period should be > > > extended as long as we are non-preempt (which we are here), > > > correct? > > > > Given Classic RCU, you are quite correct. With preemptable > > RCU, if there are no readers, and if irqs are enabled, the > > grace period could end within the spinlock's critical section. > > Of course, the spinlock would need to be held for an > > improbably long time -- many milliseconds. > > ah. But we _can_ get unlucky there and get into > multiple-milliseconds of blockage: for example if some heavy > interrupt source or softirq processes stuff for many > milliseconds. > > So it's a real fix needed both for mainline and for 2.6.28. > And kudos to kmemcheck ;-) Kudos from me as well!!! Sure beats the heck out of tracking down memory corruption by hand!!! ;-) Thanx, Paul