Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755846AbZKQSlc (ORCPT ); Tue, 17 Nov 2009 13:41:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754064AbZKQSlb (ORCPT ); Tue, 17 Nov 2009 13:41:31 -0500 Received: from smtp-out003.kontent.com ([81.88.40.217]:45988 "EHLO smtp-out003.kontent.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753639AbZKQSlb (ORCPT ); Tue, 17 Nov 2009 13:41:31 -0500 From: Oliver Neukum To: "Eric W. Biederman" Subject: Re: [PATCH] USB: ftdi_sio: Remove tty->low_latency. Date: Tue, 17 Nov 2009 19:41:34 +0100 User-Agent: KMail/1.12.2 (Linux/2.6.32-rc6-0.1-default; KDE/4.3.1; x86_64; ; ) Cc: Alan Cox , Johan Hovold , "Greg Kroah-Hartman" , Michael Trimarchi , linux-usb@vger.kernel.org, Alan Cox , Andrew Morton , linux-kernel@vger.kernel.org, Alan Stern References: <20090924154023.GA27480@localhost> <20091003140902.38628d8a@lxorguk.ukuu.org.uk> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200911171941.34781.oliver@neukum.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1277 Lines: 39 Am Dienstag, 17. November 2009 19:35:07 schrieb Eric W. Biederman: > Boiled down. ftdi_chars_in_buffer is essentially > priv->tx_outstanding_bytes. tx_outstanding_bytes is incremented when an > urb request is sent and tx_outstanding_bytes is decremented when an urb > request completes. > > It turns out I have a moderately noisy usb line, and so I occasionally > get messages like: > > ehci_hcd 0000:00:0a.1: detected XactErr len 0/7 retry 31 > > Which as best as I can tell result in the urb getting abandoned and > neither completed nor canceled (because we have hit the maximum > retry count and they still don't succeed). The URB should be finished with an error code in urb->status. ftdi_write_bulk_callback() does decrement the counter even in the error case. > Which appears to result in tx_outstanding_bytes getting stuck at > some positive number. Do you see this message if (status) { dbg("nonzero write bulk status received: %d", status); return; } if you enable debugging output? Regards Oliver -- 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/