Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755939AbYJ3RXa (ORCPT ); Thu, 30 Oct 2008 13:23:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754645AbYJ3RXV (ORCPT ); Thu, 30 Oct 2008 13:23:21 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:52053 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756875AbYJ3RXU (ORCPT ); Thu, 30 Oct 2008 13:23:20 -0400 Date: Thu, 30 Oct 2008 17:22:51 +0000 From: Alan Cox To: Helge Hafting Cc: Linus Torvalds , Linux Kernel Mailing List Subject: Re: Linux 2.6.28-rc2 i/o error on /dev/ttyUSB0 Message-ID: <20081030172251.2298b404@lxorguk.ukuu.org.uk> In-Reply-To: <4909EA24.2020701@aitel.hist.no> References: <4906F54A.7020909@aitel.hist.no> <20081028170605.611c7759@lxorguk.ukuu.org.uk> <490856FA.20609@aitel.hist.no> <20081030155412.33d57ca0@lxorguk.ukuu.org.uk> <4909EA24.2020701@aitel.hist.no> X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.12; x86_64-redhat-linux-gnu) Organization: Red Hat UK Cyf., Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, Y Deyrnas Gyfunol. Cofrestrwyd yng Nghymru a Lloegr o'r rhif cofrestru 3798903 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1264 Lines: 29 > It looks partially fixed. > No more I/O errors, and the gps unit works fine. > > But look at the attached dmesg file - there are WARNINGs still. Thats an unrelated and long long standing bug - the USB serial close paths are all racy versus the received URB handlers. The only reason you now will occasionally get a warning message is that we bother to actually trap the case rather than praying silently it doesn't blow up. What actually occurs is that you enter usb-serial:usb_serial_close which then drops port->port.count and calls type->close. Somewhere in there new data arrives and the ldisc path gets to run. The n_tty path tries to echo back bytes to the (closed) port and the WARN triggers. Changing the order to clear the port->tty first requires auditing each and every USB serial driver close method so isn't planned for this release - but its not caused major disasters in the past few years the race has been there. I can push patches this release for it if Linus particularly wants however. Alan -- 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/