Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753145AbZA1SeZ (ORCPT ); Wed, 28 Jan 2009 13:34:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751240AbZA1SeR (ORCPT ); Wed, 28 Jan 2009 13:34:17 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.125]:57293 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751524AbZA1SeQ (ORCPT ); Wed, 28 Jan 2009 13:34:16 -0500 Date: Wed, 28 Jan 2009 13:34:13 -0500 (EST) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Arjan van de Ven cc: Peter Zijlstra , LKML , Linus Torvalds , Ingo Molnar , Thomas Gleixner , Andrew Morton , Rusty Russell , jens.axboe@oracle.com Subject: Re: Buggy IPI and MTRR code on low memory In-Reply-To: <20090128102208.68a900cc@infradead.org> Message-ID: References: <1233161182.10992.52.camel@laptop> <20090128102208.68a900cc@infradead.org> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1200 Lines: 34 On Wed, 28 Jan 2009, Arjan van de Ven wrote: > On Wed, 28 Jan 2009 12:24:48 -0500 (EST) > Steven Rostedt wrote: > > > > --- > > I'll have skip the NMI test and see if it locks up any place else. > > if you get an NMI during MTRR changing you are more or less screwed. > Really. (the cpu is uncachable etc) Heh, the NMI is just another place that has the IPI problem. A different issue to the MTRR. Well, same bug, different place. > > the MTRR code should disable NMIs as much as possible. > > and for sure in -RT, the MTRR change section should not be preemptable > at all. Yeah, that is why I found this. The current code calls kfree and such from the IPI if it is allocated (not to mention the kmalloc in smp_call_function. Both of which can sleep in RT. I was forcing the data=NULL case in RT to keep it from entering the allocation code paths. But this is where I found the deadlock with MTRR (and NMI). -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/