From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1Kaw3g-0003Qk-5x for user-mode-linux-devel@lists.sourceforge.net; Wed, 03 Sep 2008 10:22:20 -0700 Received: from saraswathi.solana.com ([198.99.130.12]) by mail.sourceforge.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.44) id 1Kaw3e-0003NN-Js for user-mode-linux-devel@lists.sourceforge.net; Wed, 03 Sep 2008 10:22:20 -0700 Date: Wed, 3 Sep 2008 13:21:52 -0400 From: Jeff Dike Message-ID: <20080903172152.GB8769@c2.user-mode-linux.org> References: <20080818230509.23819.90290.reportbug@carrera.home.cobb.me.uk> <20080819120155.GD7425@inferi.kami.home> <20080826202239.GG24342@c2.user-mode-linux.org> <200809030001.20439.g+debian@cobb.uk.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <200809030001.20439.g+debian@cobb.uk.net> Subject: Re: [uml-devel] [Pkg-uml-pkgs] Bug#495611: user-mode-linux: page_mapcount(page) went negative! List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-bounces@lists.sourceforge.net Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net To: Graham Cobb Cc: Mattia Dongili , 495611@bugs.debian.org, UML-devel On Wed, Sep 03, 2008 at 12:01:19AM +0100, Graham Cobb wrote: > The bisection is complete. It took longer than I expected as many of the > versions git-bisect wanted to test would not build UML without tracking down > some additional patches. > > The bug seems to have been introduced with git commit > 3963333fe6767f15141ab2dc3b933721c636c212 (uml: cover stubs with a VMA). Excellent, the backtrace now makes a bit of sense. It looks like the VMAs at the top of the address space are being overmapped by a call to mmap. The question is why does it look like there's a big enough hole there, when it ends up unmapping the stubs in order to make room for the mmap. > With hindsight I suppose I could have guessed that would be the commit: the > crash seemed to be when unmapping a VMA. If my reading of the page flags is > correct the problem is that the page has the PG_reserved flag set, so what is > it doing in the VMA which is being unmapped? A page of kernel code is mapped into the process. This page (and all other pages containing kernel text) is marked reserved during boot. > Let me know if you want me to run some more tests, for example if you want to > add some printk's in the code to understand more about what is going on. I'm going to need some more information. I'll get back to you with a patch... Jeff -- Work email - jdike at linux dot intel dot com ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel