Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261890AbVDOSHi (ORCPT ); Fri, 15 Apr 2005 14:07:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261893AbVDOSHg (ORCPT ); Fri, 15 Apr 2005 14:07:36 -0400 Received: from mx1.redhat.com ([66.187.233.31]:24806 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S261890AbVDOSHY (ORCPT ); Fri, 15 Apr 2005 14:07:24 -0400 Date: Fri, 15 Apr 2005 14:07:03 -0400 From: Dave Jones To: Hugh Dickins Cc: Chris Wright , Andi Kleen , "Sergey S. Kostyliov" , Clem Taylor , linux-kernel@vger.kernel.org Subject: Re: x86-64 bad pmds in 2.6.11.6 II Message-ID: <20050415180703.GA26289@redhat.com> Mail-Followup-To: Dave Jones , Hugh Dickins , Chris Wright , Andi Kleen , "Sergey S. Kostyliov" , Clem Taylor , linux-kernel@vger.kernel.org References: <20050407062928.GH24469@wotan.suse.de> <20050414170117.GD22573@wotan.suse.de> <20050414181015.GH22573@wotan.suse.de> <20050414181133.GA18221@wotan.suse.de> <20050414182712.GG493@shell0.pdx.osdl.net> <20050415172408.GB8511@wotan.suse.de> <20050415172816.GU493@shell0.pdx.osdl.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1715 Lines: 37 On Fri, Apr 15, 2005 at 06:58:20PM +0100, Hugh Dickins wrote: > > > If there was a fix for the bad pmd problem it might be a candidate > > > for stable, but so far we dont know what causes it yet. > > If I figure a way to trigger here, I'll report back. > > Dave, earlier on you were quite able to reproduce the problem on 2.6.11, > finding it happened the first time you ran X. Do you have any time to > reverify that, then try to reproduce with the load_cr3 in leave_mm patch? > > But please don't waste your time on this unless you think it's plausible. I used to be able to reproduce it 100% by doing this on an vanilla upstream kernel. Then it changed behaviour so I only saw it happening on the Fedora kernel. For the latest Fedora update kernel I backported this change.. - x86_64: Only free PMDs and PUDs after other CPUs have been flushed as a 'try it and see'. At first I thought it killed the bug, but a day or so later, it started doing it again. In the Fedora kernel we have a patch which restricts /dev/mem reading, so I got suspicious about this interacting with any of the changes that had happened to drivers/char/mem.c Out of curiousity, I backported the 3-4 patches from .12rc to the Fedora .11 kernel, and haven't seen the problem since. The bizarre thing is I can't explain why any of those patches would make such a difference. Given the bug seems to be coming and going for me, its possible its just masked the problem. Dave - 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/