From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755577Ab3BDTXD (ORCPT ); Mon, 4 Feb 2013 14:23:03 -0500 Received: from mail.kernel.org ([198.145.19.201]:47926 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754782Ab3BDTXA (ORCPT ); Mon, 4 Feb 2013 14:23:00 -0500 Date: Mon, 4 Feb 2013 11:25:14 -0800 From: Greg KH To: Alexander Holler Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org, Florian Tobias Schandinat , Bernie Thompson , Steve Glendinning , stable@vger.kernel.org Subject: Re: [PATCH 2/3 v2] fb: udlfb: fix hang at disconnect Message-ID: <20130204192514.GA32318@kroah.com> References: <1359139768-32294-2-git-send-email-holler@ahsoftware.de> <20130128162238.7fba92fe.akpm@linux-foundation.org> <51071E21.9030008@ahsoftware.de> <5107A5ED.7020009@ahsoftware.de> <5107AE4F.9000809@ahsoftware.de> <5107F014.4030704@ahsoftware.de> <5108329E.2050802@ahsoftware.de> <20130204011413.GA6413@kroah.com> <510FA409.2080201@ahsoftware.de> <51100930.6080405@ahsoftware.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51100930.6080405@ahsoftware.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 04, 2013 at 08:17:04PM +0100, Alexander Holler wrote: > Am 04.02.2013 13:05, schrieb Alexander Holler: > >Am 04.02.2013 02:14, schrieb Greg KH: > > > >>So you are right in that your driver will wait for forever for a > >>disconnect() to happen, as it will never be called. I don't understand > >>the problem that this is causing when it happens. What's wrong with > >>udlfb that having the cpu suddently reset as the powerdown happened > >>without it knowing about it? > > > >There is nothing wrong with that. I've just explained why a problem > >doesn't occur on shutdown but on disconnect (of the device). > > Maybe my explanation before was just to long and I try to explain it > a bit shorter: > > If a device gets disconnected, the disconnect in udlfb might wait > forever in down_interruptible() (because it waits for an urb it > never receives). This even prevents a shutdown afterwards, because > that down_interruptible() never receives a signal (at shutdown, > because kernel threads don't get such). Where was that urb when the disconnect happened? The USB core should call your urb callback for any outstanding urbs at that point in time, with the proper error flag being set, are you handling that properly? thanks, greg k-h