lkml.org 
[lkml]   [2018]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: kobject lifetime issues in blk-mq
    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] <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)
    > >
    >
    > 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.


    Thanks,
    Ming

    \
     
     \ /
      Last update: 2018-11-12 10:45    [W:2.458 / U:0.188 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site