From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20B0FC43441 for ; Tue, 13 Nov 2018 00:22:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CBE4A22507 for ; Tue, 13 Nov 2018 00:22:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CBE4A22507 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730760AbeKMKSN (ORCPT ); Tue, 13 Nov 2018 05:18:13 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39626 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727250AbeKMKSM (ORCPT ); Tue, 13 Nov 2018 05:18:12 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 245A84E90D; Tue, 13 Nov 2018 00:22:41 +0000 (UTC) Received: from ming.t460p (ovpn-8-17.pek2.redhat.com [10.72.8.17]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 896865D739; Tue, 13 Nov 2018 00:22:31 +0000 (UTC) Date: Tue, 13 Nov 2018 08:22:27 +0800 From: Ming Lei To: Greg Kroah-Hartman Cc: Guenter Roeck , Ming Lei , Jens Axboe , Peter Zijlstra , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Hannes Reinecke , Paolo Bonzini , Christoph Hellwig , "Martin K. Petersen" , "James E.J. Bottomley" , linux-scsi@vger.kernel.org Subject: Re: kobject lifetime issues in blk-mq Message-ID: <20181113002226.GA4455@ming.t460p> References: <20181109203518.GA7130@roeck-us.net> <20181112092051.GA391@ming.t460p> <20181112094406.GB391@ming.t460p> <20181112164848.GA1790@roeck-us.net> <20181112200236.GA4415@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181112200236.GA4415@kroah.com> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Tue, 13 Nov 2018 00:22:41 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 12, 2018 at 12:02:36PM -0800, Greg Kroah-Hartman wrote: > On Mon, Nov 12, 2018 at 08:48:48AM -0800, Guenter Roeck wrote: > > On Mon, Nov 12, 2018 at 05:44:07PM +0800, Ming Lei wrote: > > > On Mon, Nov 12, 2018 at 05:20:51PM +0800, Ming Lei wrote: > > > > On Fri, Nov 09, 2018 at 12:35:18PM -0800, Guenter Roeck wrote: > > > > > Hi, > > > > > > > > > > Images with CONFIG_DEBUG_KOBJECT=y, CONFIG_DEBUG_KOBJECT_RELEASE=y > > > > > enabled report kobject lifetime issues when booting an image in qemu > > > > > using virtio-scsi-pci. > > > > > > > > > > Bisect points to two different commits, depending on the kernel > > > > > configuration. > > > > > > > > > > 1st configuration: defconfig plus: > > > > > > > > > > CONFIG_VIRTIO_BLK=y > > > > > CONFIG_SCSI_LOWLEVEL=y > > > > > CONFIG_SCSI_VIRTIO=y > > > > > CONFIG_VIRTIO_PCI=y > > > > > CONFIG_VIRTIO_MMIO=y > > > > > CONFIG_DEBUG_OBJECTS=y > > > > > CONFIG_DEBUG_OBJECTS_FREE=y > > > > > CONFIG_DEBUG_OBJECTS_TIMERS=y > > > > > CONFIG_DEBUG_KOBJECT=y > > > > > CONFIG_DEBUG_KOBJECT_RELEASE=y > > > > > > > > > > Bisecting this configuration points to commit b5b6e8c8d3b4 ("scsi: > > > > > virtio_scsi: fix IO hang caused by automatic irq vector affinity") > > > > > as the culprit. This commit enforces the use of blk-mq for virtio_scsi; > > > > > the bisect log is therefore a bit misleading. > > > > > > > > > > 2nd configuration: As above, plus: > > > > > CONFIG_SCSI_MQ_DEFAULT=y > > > > > > > > > > With this configuration, bisect points to commit 7ea5fe31c12d > > > > > ("blk-mq: make lifetime consitent between q/ctx and its kobject"). > > > > > > > > > > The qemu command line used to reproduce the problem is as follows. > > > > > The qemu version does not seem to matter (I tested with qemu versions > > > > > 2.5, 2.11, and 3.0). > > > > > > > > > > qemu-system-x86_64 \ > > > > > -kernel arch/x86/boot/bzImage \ > > > > > -device virtio-scsi-pci,id=scsi \ > > > > > -device scsi-hd,bus=scsi.0,drive=d0 \ > > > > > -drive file=./wheezy.img,format=raw,if=none,id=d0 \ > > > > > -snapshot \ > > > > > -m 2G -smp 4 -enable-kvm \ > > > > > -net user,host=10.0.2.10,hostfwd=tcp::10022-:22 -net nic \ > > > > > -nographic -monitor none \ > > > > > -no-reboot \ > > > > > -append "console=ttyS0 root=/dev/sda earlyprintk=serial panic_on_warn=1 panic=-1" > > > > > > > > > > Root file system: > > > > > https://storage.googleapis.com/syzkaller/wheezy.img > > > > > or: > > > > > https://github.com/groeck/linux-build-test/blob/master/rootfs/x86_64/rootfs.ext2.gz > > > > > > > > > > It seems that any root file system can be used to reproduce the problem. > > > > > Also, the problem is not limited to virtio-scsi-pci. I also tried > > > > > am53c974, lsi53c810, and lsi53c895a (after enabling the respective > > > > > drivers), with the same result. > > > > > > > > > > Overall, this suggests that the problem is related to blk-mq and was > > > > > indeed introduced with commit 7ea5fe31c12d. > > > > > > > > > > For reference, I attached an actual crash log as well as a set of bisect > > > > > logs below. > > > > > > > > > > Unfortunately, my understanding of blk-mq is not good enough to find the > > > > > underlying problem and suggest a fix. Please let me know if there is > > > > > anything else I can do to help fixing the problem. > > > > > > > > > > Note that the problem was originally reported by syzbot running a test > > > > > on chromeos-4.14. It may well be that the problem has already been > > > > > reported and is being worked on. If so, please apologize the noise. > > > > > > > > > > Thanks, > > > > > Guenter > > > > > > > > > > --- > > > > > [ 8.700038] ------------[ cut here ]------------ > > > > > [ 8.700376] ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x10 > > > > > [ 8.701032] WARNING: CPU: 0 PID: 0 at lib/debugobjects.c:329 debug_print_object+0x6a/0x80 > > > > > [ 8.701032] Kernel panic - not syncing: panic_on_warn set ... > > > > > [ 8.701032] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.20.0-rc1 #30 > > > > > [ 8.701032] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 > > > > > [ 8.701032] Call Trace: > > > > > [ 8.701032] > > > > > [ 8.701032] dump_stack+0x46/0x5b > > > > > [ 8.701032] panic+0xf3/0x246 > > > > > [ 8.701032] ? debug_print_object+0x6a/0x80 > > > > > [ 8.701032] __warn+0xeb/0xf0 > > > > > [ 8.701032] ? debug_print_object+0x6a/0x80 > > > > > [ 8.701032] ? debug_print_object+0x6a/0x80 > > > > > [ 8.701032] report_bug+0xb1/0x120 > > > > > [ 8.701032] fixup_bug.part.10+0x13/0x30 > > > > > [ 8.701032] do_error_trap+0x8f/0xb0 > > > > > [ 8.701032] do_invalid_op+0x31/0x40 > > > > > [ 8.701032] ? debug_print_object+0x6a/0x80 > > > > > [ 8.701032] invalid_op+0x14/0x20 > > > > > [ 8.701032] RIP: 0010:debug_print_object+0x6a/0x80 > > > > > [ 8.701032] Code: 8b 43 10 83 c2 01 8b 4b 14 89 15 c1 e2 78 01 4c 8b 45 00 4c > > > > > 89 e6 48 c7 c7 f0 ca 41 a6 48 8b 14 c5 a0 f7 24 a6 e8 06 8e cc ff <0f> 0b 5b 83 > > > > > 05 70 47 1a 01 01 5d 41 5c c3 83 05 65 47 1a 01 01 c3 > > > > > [ 8.701032] RSP: 0018:ffff89b9fda03e48 EFLAGS: 00010082 > > > > > [ 8.701032] RAX: 0000000000000000 RBX: ffff89b9fd49d0c8 RCX: ffffffffa6646e18 > > > > > [ 8.701032] RDX: 0000000000000001 RSI: 0000000000000082 RDI: ffffffffa6cc596c > > > > > [ 8.701032] RBP: ffffffffa664a5c0 R08: 79616c6564203a74 R09: 5f6b726f775f6465 > > > > > [ 8.701032] R10: ffff89b9fda03f10 R11: 3178302f3078302b R12: ffffffffa6403e22 > > > > > [ 8.701032] R13: 0000000000000001 R14: ffffffffa6d4d458 R15: ffff89b9fc4c8780 > > > > > [ 8.701032] ? debug_print_object+0x6a/0x80 > > > > > [ 8.701032] debug_check_no_obj_freed+0x1b8/0x1ea > > > > > [ 8.701032] ? rcu_process_callbacks+0x2a7/0x750 > > > > > [ 8.701032] kmem_cache_free+0x6e/0x1a0 > > > > > [ 8.701032] ? __blk_release_queue+0x150/0x150 > > > > > [ 8.701032] rcu_process_callbacks+0x2a7/0x750 > > > > > [ 8.701032] __do_softirq+0xf2/0x2c7 > > > > > [ 8.701032] irq_exit+0xb7/0xc0 > > > > > [ 8.701032] smp_apic_timer_interrupt+0x67/0x130 > > > > > [ 8.701032] apic_timer_interrupt+0xf/0x20 > > > > > [ 8.701032] > > > > > [ 8.701032] RIP: 0010:default_idle+0x12/0x140 > > > > > [ 8.701032] Code: fe ff ff c6 43 08 00 fb eb b0 31 c0 eb b4 e8 65 c8 60 ff 90 > > > > > 90 90 90 90 41 54 55 53 65 8b 2d 15 c4 3b 5a 66 66 66 66 90 fb f4 <65> 8b 2d 07 > > > > > c4 3b 5a 66 66 66 66 90 5b 5d 41 5c c3 65 8b 05 f6 c3 > > > > > [ 8.701032] RSP: 0018:ffffffffa6603e98 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 > > > > > [ 8.701032] RAX: ffffffffa5c52d10 RBX: 0000000000000000 RCX: 0000000000000000 > > > > > [ 8.701032] RDX: 0000000000000001 RSI: 0000000000000000 RDI: 000000020605092a > > > > > [ 8.701032] RBP: 0000000000000000 R08: ffffffffcff7766a R09: ffff89b9fda20b00 > > > > > [ 8.701032] R10: 0000000000000000 R11: 0000000000002400 R12: ffffffffa6611740 > > > > > [ 8.701032] R13: 0000000000000000 R14: 0000000000000000 R15: ffffffffa6611740 > > > > > [ 8.701032] ? __sched_text_end+0x5/0x5 > > > > > [ 8.701032] do_idle+0x19c/0x230 > > > > > [ 8.701032] cpu_startup_entry+0x14/0x20 > > > > > [ 8.701032] start_kernel+0x491/0x4b1 > > > > > [ 8.701032] secondary_startup_64+0xa4/0xb0 > > > > > [ 8.701032] Kernel Offset: 0x24200000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) > > > > > > > > > > > > > That is simply caused by enabling DEBUG_KOBJECT_RELEASE itself, which > > > > tries to do kboject_release() after delaying a while. > > > > > > > > Wrt. this issue, q->mq_kobj is embedded in 'request_queue' whose > > > > instance is freed in release handler of q->kobj. So when one instance > > > > of 'request_queue' is freed, DEBUG_KOBJECT_RELEASE still expects that > > > > the q->mq_kobj is active. > > > > > > > > The release handler of q->mq_kobj is NOP actually, so in reality it won't > > > > be one issue at all. > > > > > > Given we have removed legacy IO path completely, it should be fine to > > > remove q->mq_kobj and simply put everything under the kobj of queue, > > > especially any attributes under mq aren't marked as stable ABI. > > > > That might be possible going forward, but that does not appear to be > > a feasible solution for stable releases. I am not sure though if the > > "stable ABI" argument is valid. Almost all sysfs attributes are not > > marked stable. If there are applications using it, removing the atttributes > > would still break userspace. > > Yeah, don't move attributes around for no good reason, you will make > userspace grumpy :) There are very less attributes left under /sys/block/$DEV/mq. > > > Since the release function of mq_kobj is NOP (for reference, I assume > > we are talking about blk_mq_sysfs_release), can it just be NULL ? > > Someone tried to work around the internal kernel warning that comes > about when you set a release function to NULL. As per the in-kernel > documentation, I now get to make fun of that author by saying "do you > think I added those checks and message just for no good reason? Don't > try to be smarter than the driver core by providing an empty release > function to make the kernel be quiet. That's NOT what the kernel is > trying to tell you here at all." > > So fix this, that is the correct thing to do. Memory is freed in a > release function, to not do so is almost always a sign of a design bug. The root cause is that both q->kobj and q->mq_kobj are bound to lifetime of same 'request_queue' instance. We may allocate q->mq_kobj dynamically to fix this issue. And now all drivers are converted to mq, and it is really necessary to keep 'q->mq_kobj' > > > That it is an empty function seems to be just as good or bad as having > > no function at all. An empty function just avoids the "broken" debug > > message. That message is still better than rendering DEBUG_KOBJECT_RELEASE > > useless. > > > > Copying GregKH for input. > > Thanks, this code is broken and needs to be fixed. I will post a patch to address the 'issue'. Thanks, Ming