From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751932Ab1GYE7B (ORCPT ); Mon, 25 Jul 2011 00:59:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1026 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751066Ab1GYE6y (ORCPT ); Mon, 25 Jul 2011 00:58:54 -0400 Date: Mon, 25 Jul 2011 00:58:52 -0400 From: Dave Jones To: Al Viro Cc: Linux Kernel Subject: Re: kdevtmpfs oops since yesterdays vfs merge Message-ID: <20110725045851.GA11267@redhat.com> Mail-Followup-To: Dave Jones , Al Viro , Linux Kernel References: <20110724231701.GA1707@redhat.com> <20110724232812.GN24703@ZenIV.linux.org.uk> <20110724234029.GA4881@redhat.com> <20110724235154.GO24703@ZenIV.linux.org.uk> <20110725015324.GA7603@redhat.com> <20110725015612.GB7603@redhat.com> <20110725024444.GP24703@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110725024444.GP24703@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 25, 2011 at 03:44:44AM +0100, Al Viro wrote: > > when it triggers the bug_on(), it's that second nodename that is garbage. > > Interesting... The next experiment would be to stick BUG_ON(!req.dev) > into devtmpfs_create_node() right after the assigment to that field. couldn't get that to trigger. > We couldn't be hit by the lack of barriers here, could we? Store to > req.dev happens before spin_unlock(&req_lock), so by the time when > that request is seen by loop in devtmpfsd() and passed to handle() it > should be seen - we have grabbed req_lock, found a pointer to req, dropped > req_lock and called handle(). Should've been enough... > > Might be interesting to print &req from devtmpfs_create_node(), both on > entry and on exit, and print req right before the call of handle()... Here's latest.. https://s3.amazonaws.com/twitpic/photos/full/355219312.jpg?AWSAccessKeyId=AKIAJF3XCCKACR3QDMOA&Expires=1311570683&Signature=xr3tusulMiV2bIsxux9YNrawUDA%3D apologies for crappy picture, but it's legible at fullsize.. interesting thing here is that the req that causes the oops, I couldn't find any call to create_handle for that address, so where devtmpfsd got it is a mystery. The address is curious too, in that it's way off from all the reqs created around that time. I'll add some more printk's to see if I can figure where that's being created. Dave