Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758881Ab3GaCdt (ORCPT ); Tue, 30 Jul 2013 22:33:49 -0400 Received: from mail-qa0-f54.google.com ([209.85.216.54]:37362 "EHLO mail-qa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751600Ab3GaCdr (ORCPT ); Tue, 30 Jul 2013 22:33:47 -0400 MIME-Version: 1.0 In-Reply-To: References: <1375204090-27465-1-git-send-email-jwerner@chromium.org> Date: Tue, 30 Jul 2013 19:33:46 -0700 X-Google-Sender-Auth: -vSTCw8Uq-KpHjhbk7S1Yv9pOKc Message-ID: Subject: Re: [PATCH] usb: core: don't try to reset_device() a port that got just disconnected From: Julius Werner To: Alan Stern Cc: Julius Werner , Greg Kroah-Hartman , LKML , linux-usb@vger.kernel.org, Sarah Sharp , Vincent Palatin , Benson Leung Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1432 Lines: 29 > Wait a moment. Why does each of these attempts lead to a 5-second > timeout? Why don't they fail immediately? Now that you mention it, that's a very good question. The kernel enqueues a control transfer to the now disconnected address because it's internal bookkeeping is not yet updated, but I guess that should usually fail very fast from an xHC-internal transaction timeout. I have now tried to debug the cause of this: I see the transfer being enqueued and the doorbell triggered, but never get a transfer event back from it (until the software timeout calls usb_kill_urb() which stops the endpoint). With the same setup on a PantherPoint system I get the same U1/U2 disable control messages on unplugging, but they fail within <5ms with a transaction error... so I guess this must be a LynxPoint hardware bug. Regardless, calling usb_reset_device() is still wrong and will at least lead to pointless transfer attempts and error messages, so I think my patch still has merit. > What will happen here if udev is NULL? Maybe you should change the > test to (!udev || !(portstatus & ...)). Right... I'm not sure if that can happen in practice, but I'll change it just in case. -- 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/