From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932825AbaIEPRv (ORCPT ); Fri, 5 Sep 2014 11:17:51 -0400 Received: from icebox.esperi.org.uk ([81.187.191.129]:58554 "EHLO mail.esperi.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932211AbaIEPRu (ORCPT ); Fri, 5 Sep 2014 11:17:50 -0400 From: Nix To: Oliver Neukum Cc: linux-kernel@vger.kernel.org Subject: Re: [3.16.1 REGRESSION]: Simtec Entropy Key (cdc-acm) broken in 3.16 References: <878um4tg09.fsf@spindle.srvr.nix> <1409569752.24385.12.camel@linux-fkkt.site> <874mwnosz1.fsf@spindle.srvr.nix> <1409903983.9532.0.camel@linux-fkkt.site> Emacs: where editing text is like playing Paganini on a glass harmonica. Date: Fri, 05 Sep 2014 16:17:47 +0100 In-Reply-To: <1409903983.9532.0.camel@linux-fkkt.site> (Oliver Neukum's message of "Fri, 05 Sep 2014 09:59:43 +0200") Message-ID: <8761h2nlk4.fsf@spindle.srvr.nix> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-DCC-INFN-TO-Metrics: spindle 1233; Body=2 Fuz1=2 Fuz2=2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5 Sep 2014, Oliver Neukum verbalised: > On Fri, 2014-09-05 at 00:40 +0100, Nix wrote: >> I'm working around this confusing morass by rebooting into each test >> kernel, unplugging and replugging the entropy key if it was fubared, >> then rebooting into the same kernel again and seeing if it was still >> fubared. But this is not terribly fast, particularly not on a headless >> compact-flash-based Geode box which doesn't even complete booting >> without the entropy source which this bug cuts off :) so it'll be >> sometime tomorrow before I can get this bisection done, I'm afraid. > > Ugh. My sympathies. I cannot suggest a better method, I am afraid. Well, that method doesn't work. I've found pairs of kernels (e.g. 59a3d4c3631e553357b7305dc09db1990aa6757c and b05d59dfceaea72565b1648af929b037b0f96d7f) where each kernel works on its own (rebooting from that kernel into the same kernel keeps a working key, so I would normally assume that each kernel is OK) but rebooting from the first into the second yields a broken one if it was working before (so one of them must, in fact, be broken, but I have no clue which one). So I can't figure out how to bisect this. Any suggestions as to what failure-test I might use, or what other methods I might use to figure out what's going wrong? Not knowing anything about USB doesn't help here. I don't know for sure that this is a cdc-acm problem -- bisecting just the cdc-acm driver was fruitless -- so it might be something more generally USBish. -- NULL && (void)