From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752219AbdATRPc (ORCPT ); Fri, 20 Jan 2017 12:15:32 -0500 Received: from mail-pf0-f174.google.com ([209.85.192.174]:36370 "EHLO mail-pf0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751201AbdATRPa (ORCPT ); Fri, 20 Jan 2017 12:15:30 -0500 Subject: Re: [lkp-robot] [rcu] b332151a29: kernel_BUG_at_mm/slab.c To: Sebastian Andrzej Siewior References: <20170119010216.GA8287@yexl-desktop> <20170120160123.z4llgm4qaaemkp52@linutronix.de> <32585b54-c2fd-66ea-e636-bdbd387133c1@kernel.dk> <20170120162354.776bf2j75o247mzu@linutronix.de> <20170120170907.u7ekube62edg32qr@linutronix.de> Cc: kernel test robot , "Paul E. McKenney" , LKML , lkp@01.org, linux-scsi@vger.kernel.org, tglx@linutronix.de, linux-block@vger.kernel.org From: Jens Axboe Message-ID: Date: Fri, 20 Jan 2017 09:15:28 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <20170120170907.u7ekube62edg32qr@linutronix.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/20/2017 09:09 AM, Sebastian Andrzej Siewior wrote: > On 2017-01-20 08:32:37 [-0800], Jens Axboe wrote: >> That's alright, sounds like it's not a -next regression, but rather something >> that is already broken. I can reproduce a lot of breakage if I enable >> CONFIG_DEBUG_TEST_DRIVER_REMOVE, in fact my system doesn't boot at all. This >> is the first bug: >> >> [ 18.247895] ------------[ cut here ]------------ >> [ 18.247907] WARNING: CPU: 21 PID: 2223 at drivers/ata/libata-core.c:6522 ata_host_detach+0x11b] >> [ 18.247908] Modules linked in: igb(+) ahci(+) libahci i2c_algo_bit dca libata nvme(+) nvme_core >> [ 18.247917] CPU: 21 PID: 2223 Comm: systemd-udevd Tainted: G W 4.10.0-rc4+ #30 >> [ 18.247919] Hardware name: Dell Inc. PowerEdge T630/0NT78X, BIOS 2.3.4 11/09/2016 >> [ 18.247919] Call Trace: >> [ 18.247928] dump_stack+0x68/0x93 >> [ 18.247934] __warn+0xc6/0xe0 >> [ 18.247937] warn_slowpath_null+0x18/0x20 >> [ 18.247943] ata_host_detach+0x11b/0x120 [libata] > … > >> and it's even more downhill from there. That option is marked unstable, are we >> expecting it to work right now? > > Well, as per 248ff0216543 ("driver core: Make Kconfig text for > DEBUG_TEST_DRIVER_REMOVE stronger"): > > | The current state of driver removal is not great. > | CONFIG_DEBUG_TEST_DRIVER_REMOVE finds lots of errors. The help text > | currently undersells exactly how many errors this option will find. Add > | a bit more description to indicate this option shouldn't be turned on > | unless you actually want to debug driver removal. The text can be > | changed later when more drivers are fixed up. > > so it looks like the option is working but it uncovers bugs. I've put > you in TO because the breakage in kvm test went away after I disabled > the MQ support in SCSI. So I *assumed* that MQ was not doing something > right in the removal path. I don't know if this libata-core backtrace is > a false positive or not. Sure, I get that, my question is just if it's always finding valid bugs, or if the test itself is buggy. The fact that I can't boot anything after enabling it makes me suspicious. Or maybe the state of load/remove/load is just pretty sad. -- Jens Axboe