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Subjectkobject lifetime issues in blk-mq
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] <IRQ>
[ 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] </IRQ>
[ 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)

---
# bad: [a351e9b9fc24e982ec2f0e76379a49826036da12] Linux 4.11
# good: [c470abd4fde40ea6a0846a2beab642a578c0b8cd] Linux 4.10
git bisect start 'v4.11' 'v4.10'
# good: [1ec5c1867af085897bb9e0f67bef3713334dbe7f] Merge tag 'gpio-v4.11-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio
git bisect good 1ec5c1867af085897bb9e0f67bef3713334dbe7f
# good: [79b17ea740d9fab178d6a1aa15d848b5e6c01b82] Merge tag 'trace-v4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
git bisect good 79b17ea740d9fab178d6a1aa15d848b5e6c01b82
# bad: [d4ee21ef61dfcaeba7542cdc1c9242364a8ca5c0] Merge tag 'reset-fixes-for-4.11-2' of git://git.pengutronix.de/git/pza/linux into fixes
git bisect bad d4ee21ef61dfcaeba7542cdc1c9242364a8ca5c0
# good: [5eca1c10cbaa9c366c18ca79f81f21c731e3dcc7] sched/headers: Clean up <linux/sched.h>
git bisect good 5eca1c10cbaa9c366c18ca79f81f21c731e3dcc7
# good: [2d62e0768d3c28536d4cfe4c40ba1e5e8e442a93] Merge tag 'kvm-4.11-2' of git://git.kernel.org/pub/scm/virt/kvm/kvm
git bisect good 2d62e0768d3c28536d4cfe4c40ba1e5e8e442a93
# bad: [9db61d6fd65f53eaee13fbb451fd761ce926dea9] Merge tag 'xfs-4.11-fixes-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux
git bisect bad 9db61d6fd65f53eaee13fbb451fd761ce926dea9
# good: [f7d6a7283aa1de430c6323a9714d1a787bc2d1ea] Merge tag 'powerpc-4.11-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
git bisect good f7d6a7283aa1de430c6323a9714d1a787bc2d1ea
# good: [ec3b93ae0bf4742e9cbb40e1964129926c1464e0] Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good ec3b93ae0bf4742e9cbb40e1964129926c1464e0
# bad: [34bbce9e344b47e8871273409632f525973afad4] Merge branch 'for-linus' of git://git.kernel.dk/linux-block
git bisect bad 34bbce9e344b47e8871273409632f525973afad4
# good: [bb61ce54e8986ea18f7eb13cfa4a6fa8eb311bbd] Merge tag 'media/v4.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
git bisect good bb61ce54e8986ea18f7eb13cfa4a6fa8eb311bbd
# bad: [b0bfdfc2bf7fa85317824c6a389fc373dfcef5bc] block/sed: Fix opal user range check and unused variables
git bisect bad b0bfdfc2bf7fa85317824c6a389fc373dfcef5bc
# bad: [6c8b232efea1ad3d263ff8b9c16b7e8767a77488] blk-mq: make lifetime consistent between hctx and its kobject
git bisect bad 6c8b232efea1ad3d263ff8b9c16b7e8767a77488
# bad: [7ea5fe31c12dd8bcf4a9c5a4a7e8e23826a9a3b8] blk-mq: make lifetime consitent between q/ctx and its kobject
git bisect bad 7ea5fe31c12dd8bcf4a9c5a4a7e8e23826a9a3b8
# good: [737f98cfe7de8df7433a4d846850aa8efa44bd48] blk-mq: initialize mq kobjects in blk_mq_init_allocated_queue()
git bisect good 737f98cfe7de8df7433a4d846850aa8efa44bd48
# first bad commit: [7ea5fe31c12dd8bcf4a9c5a4a7e8e23826a9a3b8] blk-mq: make lifetime consitent between q/ctx and its kobject

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