From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753310AbaIHH6s (ORCPT ); Mon, 8 Sep 2014 03:58:48 -0400 Received: from icebox.esperi.org.uk ([81.187.191.129]:38564 "EHLO mail.esperi.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752809AbaIHH6r (ORCPT ); Mon, 8 Sep 2014 03:58:47 -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> <8761h2nlk4.fsf@spindle.srvr.nix> <1410160901.11338.16.camel@linux-fkkt.site> Emacs: if it payed rent for disk space, you'd be rich. Date: Mon, 08 Sep 2014 08:58:44 +0100 In-Reply-To: <1410160901.11338.16.camel@linux-fkkt.site> (Oliver Neukum's message of "Mon, 08 Sep 2014 09:21:41 +0200") Message-ID: <87sik2czm3.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-wuwien-Metrics: spindle 1290; Body=2 Fuz1=2 Fuz2=2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8 Sep 2014, Oliver Neukum said: > On Fri, 2014-09-05 at 16:17 +0100, Nix wrote: >> 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. > > Do your kernels work if you start with a known good kernel e.g. > 3.15 and then reboot? That case works -- aha, so I could orchestrate it by going 3.15 -> test -> test -> reset to 3.15 -> test -> test ... i.e. a triple reboot cycle. Should have thought of that. God, what a pain :) I'll give it a try tonight. -- NULL && (void)