Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754918AbZLBP6a (ORCPT ); Wed, 2 Dec 2009 10:58:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753585AbZLBP63 (ORCPT ); Wed, 2 Dec 2009 10:58:29 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:60053 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754273AbZLBP61 (ORCPT ); Wed, 2 Dec 2009 10:58:27 -0500 Date: Wed, 2 Dec 2009 10:58:28 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Ondrej Zary cc: linux-usb@vger.kernel.org, Subject: Re: debugging oops after disconnecting Nexio USB touchscreen In-Reply-To: <200912020952.09354.linux@rainbow-software.org> Message-ID: 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: 1280 Lines: 37 On Wed, 2 Dec 2009, Ondrej Zary wrote: > It shows "prev is NULL, qh=f6581080, ehci->async=f6581000". > > The problem is that activating usbmon causes the problem to disappear. No errors > in maybe 15 attempts. It appeared on 2nd attempt after unloading usbmon. Nevertheless, the usbmon output might be useful. Try going through a couple of cycles with usbmon installed, then unload usbmon and create a crash. Also, try adding some more debugging output (and let's hope it doesn't also make the problem disappear). In start_unlink_async(), just before your "after:" label, add ehci_info(ehci, "unlink qh %p %p\n", qh, qh->qh_next); In qh_link_async(), just after the wmb(), add ehci_info(ehci, "link qh %p %p\n", qh, qh->qh_next); In end_unlink_async(), just after the iaa_watchdog_done(ehci), add ehci_info(ehci, "end unlink qh %p %p\n", qh, qh->next); And in qh_make(), just before the end, add ehci_info(ehci, "create qh %p, dev %s, ep %x\n", qh, urb->dev->devpath, urb->ep->desc.bEndpointAddress); Alan Stern -- 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/