From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753126AbaIHHxH (ORCPT ); Mon, 8 Sep 2014 03:53:07 -0400 Received: from smtp-out003.kontent.com ([81.88.40.217]:58792 "EHLO smtp-out003.kontent.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752874AbaIHHxG (ORCPT ); Mon, 8 Sep 2014 03:53:06 -0400 Message-ID: <1410160901.11338.16.camel@linux-fkkt.site> Subject: Re: [3.16.1 REGRESSION]: Simtec Entropy Key (cdc-acm) broken in 3.16 From: Oliver Neukum To: Nix Cc: linux-kernel@vger.kernel.org In-Reply-To: <8761h2nlk4.fsf@spindle.srvr.nix> 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> Content-Type: text/plain; charset="UTF-8" Date: Mon, 08 Sep 2014 09:21:41 +0200 Mime-Version: 1.0 X-Mailer: Evolution 3.10.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Regards Oliver