From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751347AbdKUUcI (ORCPT ); Tue, 21 Nov 2017 15:32:08 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:35938 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751067AbdKUUcH (ORCPT ); Tue, 21 Nov 2017 15:32:07 -0500 Subject: Re: 4.14: WARNING: CPU: 4 PID: 2895 at block/blk-mq.c:1144 with virtio-blk (also 4.12 stable) To: Jens Axboe , Bart Van Assche , "virtualization@lists.linux-foundation.org" , "linux-block@vger.kernel.org" , "mst@redhat.com" , "jasowang@redhat.com" , "linux-kernel@vger.kernel.org" , Christoph Hellwig , Greg Kroah-Hartman , stable@vger.kernel.org References: <9c5eec5d-f542-4d76-6933-6fe31203ce09@de.ibm.com> <1511205644.2396.32.camel@wdc.com> <04526c98-ffc5-1eca-3aa8-50f9212c4323@de.ibm.com> <5c9f2228-0a8b-8225-7038-e6cb3f31ca0b@kernel.dk> <2e44dbd3-2f90-c267-560c-91d1d4b0e892@de.ibm.com> <823b9dd5-7781-5a72-03ff-bc931433fc19@kernel.dk> <15f232d2-2aaa-df7c-57e8-2f710e051e84@de.ibm.com> <055f040d-3f9a-a8fd-e8e2-326c6b9094a1@kernel.dk> <1aeecf2e-a68e-4c18-5912-2473f457e6ea@de.ibm.com> <8fedc2ad-d775-7789-742c-92ca928a3aee@kernel.dk> <276625a9-44fb-719d-9281-caacefdbb99f@de.ibm.com> From: Christian Borntraeger Date: Tue, 21 Nov 2017 21:31:39 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 17112120-0016-0000-0000-000005040E87 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17112120-0017-0000-0000-0000283FDCFA Message-Id: <1ddd1cd4-2862-849e-7849-82544bcb86be@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-11-21_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1711210267 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/21/2017 09:21 PM, Jens Axboe wrote: > On 11/21/2017 01:19 PM, Christian Borntraeger wrote: >> >> On 11/21/2017 09:14 PM, Jens Axboe wrote: >>> On 11/21/2017 01:12 PM, Christian Borntraeger wrote: >>>> >>>> >>>> On 11/21/2017 08:30 PM, Jens Axboe wrote: >>>>> On 11/21/2017 12:15 PM, Christian Borntraeger wrote: >>>>>> >>>>>> >>>>>> On 11/21/2017 07:39 PM, Jens Axboe wrote: >>>>>>> On 11/21/2017 11:27 AM, Jens Axboe wrote: >>>>>>>> On 11/21/2017 11:12 AM, Christian Borntraeger wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> On 11/21/2017 07:09 PM, Jens Axboe wrote: >>>>>>>>>> On 11/21/2017 10:27 AM, Jens Axboe wrote: >>>>>>>>>>> On 11/21/2017 03:14 AM, Christian Borntraeger wrote: >>>>>>>>>>>> Bisect points to >>>>>>>>>>>> >>>>>>>>>>>> 1b5a7455d345b223d3a4658a9e5fce985b7998c1 is the first bad commit >>>>>>>>>>>> commit 1b5a7455d345b223d3a4658a9e5fce985b7998c1 >>>>>>>>>>>> Author: Christoph Hellwig >>>>>>>>>>>> Date: Mon Jun 26 12:20:57 2017 +0200 >>>>>>>>>>>> >>>>>>>>>>>> blk-mq: Create hctx for each present CPU >>>>>>>>>>>> >>>>>>>>>>>> commit 4b855ad37194f7bdbb200ce7a1c7051fecb56a08 upstream. >>>>>>>>>>>> >>>>>>>>>>>> Currently we only create hctx for online CPUs, which can lead to a lot >>>>>>>>>>>> of churn due to frequent soft offline / online operations. Instead >>>>>>>>>>>> allocate one for each present CPU to avoid this and dramatically simplify >>>>>>>>>>>> the code. >>>>>>>>>>>> >>>>>>>>>>>> Signed-off-by: Christoph Hellwig >>>>>>>>>>>> Reviewed-by: Jens Axboe >>>>>>>>>>>> Cc: Keith Busch >>>>>>>>>>>> Cc: linux-block@vger.kernel.org >>>>>>>>>>>> Cc: linux-nvme@lists.infradead.org >>>>>>>>>>>> Link: http://lkml.kernel.org/r/20170626102058.10200-3-hch@lst.de >>>>>>>>>>>> Signed-off-by: Thomas Gleixner >>>>>>>>>>>> Cc: Oleksandr Natalenko >>>>>>>>>>>> Cc: Mike Galbraith >>>>>>>>>>>> Signed-off-by: Greg Kroah-Hartman >>>>>>>>>>> >>>>>>>>>>> I wonder if we're simply not getting the masks updated correctly. I'll >>>>>>>>>>> take a look. >>>>>>>>>> >>>>>>>>>> Can't make it trigger here. We do init for each present CPU, which means >>>>>>>>>> that if I offline a few CPUs here and register a queue, those still show >>>>>>>>>> up as present (just offline) and get mapped accordingly. >>>>>>>>>> >>>>>>>>>> From the looks of it, your setup is different. If the CPU doesn't show >>>>>>>>>> up as present and it gets hotplugged, then I can see how this condition >>>>>>>>>> would trigger. What environment are you running this in? We might have >>>>>>>>>> to re-introduce the cpu hotplug notifier, right now we just monitor >>>>>>>>>> for a dead cpu and handle that. >>>>>>>>> >>>>>>>>> I am not doing a hot unplug and the replug, I use KVM and add a previously >>>>>>>>> not available CPU. >>>>>>>>> >>>>>>>>> in libvirt/virsh speak: >>>>>>>>> 4 >>>>>>>> >>>>>>>> So that's why we run into problems. It's not present when we load the device, >>>>>>>> but becomes present and online afterwards. >>>>>>>> >>>>>>>> Christoph, we used to handle this just fine, your patch broke it. >>>>>>>> >>>>>>>> I'll see if I can come up with an appropriate fix. >>>>>>> >>>>>>> Can you try the below? >>>>>> >>>>>> >>>>>> It does prevent the crash but it seems that the new CPU is not "used " after the hotplug for mq: >>>>>> >>>>>> >>>>>> output with 2 cpus: >>>>>> /sys/kernel/debug/block/vda >>>>>> /sys/kernel/debug/block/vda/hctx0 >>>>>> /sys/kernel/debug/block/vda/hctx0/cpu0 >>>>>> /sys/kernel/debug/block/vda/hctx0/cpu0/completed >>>>>> /sys/kernel/debug/block/vda/hctx0/cpu0/merged >>>>>> /sys/kernel/debug/block/vda/hctx0/cpu0/dispatched >>>>>> /sys/kernel/debug/block/vda/hctx0/cpu0/rq_list >>>>>> /sys/kernel/debug/block/vda/hctx0/active >>>>>> /sys/kernel/debug/block/vda/hctx0/run >>>>>> /sys/kernel/debug/block/vda/hctx0/queued >>>>>> /sys/kernel/debug/block/vda/hctx0/dispatched >>>>>> /sys/kernel/debug/block/vda/hctx0/io_poll >>>>>> /sys/kernel/debug/block/vda/hctx0/sched_tags_bitmap >>>>>> /sys/kernel/debug/block/vda/hctx0/sched_tags >>>>>> /sys/kernel/debug/block/vda/hctx0/tags_bitmap >>>>>> /sys/kernel/debug/block/vda/hctx0/tags >>>>>> /sys/kernel/debug/block/vda/hctx0/ctx_map >>>>>> /sys/kernel/debug/block/vda/hctx0/busy >>>>>> /sys/kernel/debug/block/vda/hctx0/dispatch >>>>>> /sys/kernel/debug/block/vda/hctx0/flags >>>>>> /sys/kernel/debug/block/vda/hctx0/state >>>>>> /sys/kernel/debug/block/vda/sched >>>>>> /sys/kernel/debug/block/vda/sched/dispatch >>>>>> /sys/kernel/debug/block/vda/sched/starved >>>>>> /sys/kernel/debug/block/vda/sched/batching >>>>>> /sys/kernel/debug/block/vda/sched/write_next_rq >>>>>> /sys/kernel/debug/block/vda/sched/write_fifo_list >>>>>> /sys/kernel/debug/block/vda/sched/read_next_rq >>>>>> /sys/kernel/debug/block/vda/sched/read_fifo_list >>>>>> /sys/kernel/debug/block/vda/write_hints >>>>>> /sys/kernel/debug/block/vda/state >>>>>> /sys/kernel/debug/block/vda/requeue_list >>>>>> /sys/kernel/debug/block/vda/poll_stat >>>>> >>>>> Try this, basically just a revert. >>>> >>>> Yes, seems to work. >>>> >>>> Tested-by: Christian Borntraeger >>> >>> Great, thanks for testing. >>> >>>> Do you know why the original commit made it into 4.12 stable? After all >>>> it has no Fixes tag and no cc stable- >>> >>> I was wondering the same thing when you said it was in 4.12.stable and >>> not in 4.12 release. That patch should absolutely not have gone into >>> stable, it's not marked as such and it's not fixing a problem that is >>> stable worthy. In fact, it's causing a regression... >>> >>> Greg? Upstream commit is mentioned higher up, start of the email. >>> >> >> >> Forgot to cc Greg? > > I did, thanks for doing that. Now I wonder how to mark this patch, > as we should revert it from kernels that have the bad commit. 4.12 > is fine, 4.12.later-stable is not. > I think we should tag it with: Fixes: 4b855ad37194 ("blk-mq: Create hctx for each present CPU") which should bring it into 4.13 stable and 4.14 stable. 4.12 stable seems EOL anyway.