From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966348AbbDQO0n (ORCPT ); Fri, 17 Apr 2015 10:26:43 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:16347 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966319AbbDQO0k (ORCPT ); Fri, 17 Apr 2015 10:26:40 -0400 Message-ID: <55311803.9030105@fb.com> Date: Fri, 17 Apr 2015 08:26:11 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Guenter Roeck , CC: Chong Yuan , Wenbo Wang Subject: Re: Upstream kernel fails to run on qemu-sparc64 due to commit 889fa31f0 (blk-mq: reduce unnecessary software queue looping) References: <20150417063220.GA2871@roeck-us.net> <20150417133204.GA29300@roeck-us.net> In-Reply-To: <20150417133204.GA29300@roeck-us.net> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.54.13] X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.13.68,1.0.33,0.0.0000 definitions=2015-04-17_05:2015-04-17,2015-04-17,1970-01-01 signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/17/2015 07:32 AM, Guenter Roeck wrote: > On Thu, Apr 16, 2015 at 11:32:20PM -0700, Guenter Roeck wrote: >> Hi, >> >> my qemu-sparc64 tests fail to run with kernel v4.0-7245-ga39ef1a7c609. >> Bisect points to commit 889fa31f00b ("blk-mq: reduce unnecessary software >> queue looping"). Reverting this commit fixes the problem. >> >> I had a look into the commit, but I have no idea what might be wrong. >> >> I made the bisect log, images, configuration file, root file system, and directions >> on how to run the images available at https://urldefense.proofpoint.com/v1/url?u=http://server.roeck-us.net/qemu/sparc64&k=ZVNjlDMF0FElm4dQtryO4A%3D%3D%0A&r=3JMVyziIyZtZ5cv9eWNLwQ%3D%3D%0A&m=%2FUVX9MC8j8RmqOwlL6HnyBe%2FFSO5xSJdG3GTTzADFYk%3D%0A&s=caaf39bb4246d5223f9dea93771fdb075f9046b6fdf1822b7da21d7665da71d5. >> >> Please let me know if there is any other information I can provide. >> > As additional information: > > + * Set the map size to the number of mapped software queues. > + * This is more accurate and more efficient than looping > + * over all possibly mapped software queues. > + */ > + map->map_size = hctx->nr_ctx / map->bits_per_word; > > On my system, hctx->nr_ctx is 1, and map->bits_per_word is 8. > Thus map->map_size is set to 0, which doesn't make much sense. > The system comes up if I replace the above code with > map->map_size = DIV_ROUND_UP(hctx->nr_ctx, map->bits_per_word); > > I have no idea if that is the correct fix, though. Ugh, yes indeed, looks like the <= was lost from a previous patch. Now I wonder why it I didn't see any hangs with this... Thanks for reporting, I'll get a fix in today. -- Jens Axboe