From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752454Ab2G1M1Q (ORCPT ); Sat, 28 Jul 2012 08:27:16 -0400 Received: from canardo.mork.no ([148.122.252.1]:53603 "EHLO canardo.mork.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752299Ab2G1M1P convert rfc822-to-8bit (ORCPT ); Sat, 28 Jul 2012 08:27:15 -0400 From: =?utf-8?Q?Bj=C3=B8rn_Mork?= To: Daniel Mack Cc: Alan Stern , Sarbojit Ganguly , gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Takashi Iwai Subject: Re: Kernel Oops while disconnecting USB peripheral (always) Organization: m References: <500D659E.5090207@gmail.com> Date: Sat, 28 Jul 2012 14:27:02 +0200 In-Reply-To: <500D659E.5090207@gmail.com> (Daniel Mack's message of "Mon, 23 Jul 2012 16:54:22 +0200") Message-ID: <87r4rwvzop.fsf@nemi.mork.no> User-Agent: Gnus/5.11002 (No Gnus v0.20) Emacs/23.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Daniel Mack writes: > On 23.07.2012 16:47, Alan Stern wrote: >> On Mon, 23 Jul 2012, Sarbojit Ganguly wrote: >>> That is why I provided two stacks, >>> >>> 1st one is when I tried to remove the USB hub (which connects a webcam >>> + microphone) >>> 2nd one is when I tried to remove an USB powered external HDD. >>> >>> Just to make sure whether the problem is with USB sound or the USB subsystem. >> >> Do you stop all the programs that are using the USB devices before >> unplugging the hub? Do you unmount the USB HDD first? >> >> The first crash shows a problem in the snd-usb-audio driver. >> >> The second crash shows a problem in the VFS layer or in ext3, not in >> the USB stack. > > I dare to doubt there are two severe bugs of that kind that are 100% > reproducible. I haven't had a hotplug crash in any of the two drivers > for a long time, and I use both of them extensively. Actually, based on the recent usb_wwan experience, I'd say that two such bugs isn't as unlikely as it may seem at first. Even three if we add the now fixed usb_wwan (or six, if we count the three drivers affected by the usb_wwan bug). There are probably even more. The reason is this change: 0998d0631 device-core: Ensure drvdata = NULL when no driver is bound It will make bugs like this suddenly 100% reproducible. But the bugs *are* in the drivers, and may have been there for a long time. The drivers have been accessing drvdata after unbinding. They just didn't crash prior to that commit. But the commit is correct, and a very much needed improvement if my assumptions are correct. The drivers need fixing and this just makes it evident. > I rather assume there's something else failing, probably some host > controller issue that corrupts mempory? Can anyone else reproduce this > maybe? You could of course do like me and bisect, but if you end up with commit 0998d0631 then you haven't really learned more than confirming my guess. Bjørn