Re: INFO: task hung in blk_mq_freeze_queue_wait

[Dmitry Vyukov]

On Sun, Dec 10, 2017 at 2:36 PM, syzbot
<bot+caffa2697ebe6d891ac5d7701d58644a307c470a@xxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> ad4dac17f9d563b9e34aab78a34293b10993e9b5
> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
>
> Unfortunately, I don't have any reproducer for this bug yet.
>
>
> INFO: task syz-executor4:10562 blocked for more than 120 seconds.
>       Not tainted 4.15.0-rc2-next-20171208+ #63
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> syz-executor4   D24560 10562   3357 0x00000004
> Call Trace:
>  context_switch kernel/sched/core.c:2800 [inline]
>  __schedule+0x8eb/0x2060 kernel/sched/core.c:3376
>  schedule+0xf5/0x430 kernel/sched/core.c:3435
>  blk_mq_freeze_queue_wait+0x1bb/0x400 block/blk-mq.c:137
>  blk_freeze_queue block/blk-mq.c:164 [inline]
>  blk_mq_freeze_queue+0x1d/0x20 block/blk-mq.c:173
>  loop_set_status+0x1a2/0xf60 drivers/block/loop.c:1097
>  loop_set_status64+0x95/0x100 drivers/block/loop.c:1271
>  lo_ioctl+0xd98/0x1b90 drivers/block/loop.c:1381
>  __blkdev_driver_ioctl block/ioctl.c:303 [inline]
>  blkdev_ioctl+0x1759/0x1e00 block/ioctl.c:601
>  block_ioctl+0xea/0x130 fs/block_dev.c:1860
>  vfs_ioctl fs/ioctl.c:46 [inline]
>  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
>  SYSC_ioctl fs/ioctl.c:701 [inline]
>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>  entry_SYSCALL_64_fastpath+0x1f/0x96
> RIP: 0033:0x452a39
> RSP: 002b:00007fa74b7d6c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 0000000000452a39
> RDX: 00000000202d1000 RSI: 0000000000004c04 RDI: 0000000000000014
> RBP: 000000000000055e R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f6170
> R13: 00000000ffffffff R14: 00007fa74b7d76d4 R15: 0000000000000000
>
> Showing all locks held in the system:
> 2 locks held by khungtaskd/671:
>  #0:  (rcu_read_lock){....}, at: [<00000000c846f207>]
> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
>  #0:  (rcu_read_lock){....}, at: [<00000000c846f207>] watchdog+0x1c5/0xd60
> kernel/hung_task.c:249
>  #1:  (tasklist_lock){.+.+}, at: [<000000009d31aff0>]
> debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
> 2 locks held by getty/3115:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000268943a7>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000c938216d>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3116:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000268943a7>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000c938216d>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3117:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000268943a7>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000c938216d>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3118:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000268943a7>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000c938216d>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3119:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000268943a7>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000c938216d>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3120:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000268943a7>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000c938216d>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3121:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000268943a7>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000c938216d>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 1 lock held by syz-executor4/10562:
>  #0:  (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000a39a9511>]
> lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
> 1 lock held by syz-executor4/10570:
>  #0:  (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000a39a9511>]
> lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
> 1 lock held by syz-executor4/10577:
>  #0:  (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000a39a9511>]
> lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
> 1 lock held by syz-executor4/10589:
>  #0:  (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000a39a9511>]
> lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
>
> =============================================
>
> NMI backtrace for cpu 0
> CPU: 0 PID: 671 Comm: khungtaskd Not tainted 4.15.0-rc2-next-20171208+ #63
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>  nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
>  nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:62
>  arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
>  trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
>  check_hung_task kernel/hung_task.c:132 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
>  watchdog+0x90c/0xd60 kernel/hung_task.c:249
>  kthread+0x37a/0x440 kernel/kthread.c:238
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
> Sending NMI from CPU 0 to CPUs 1:
> NMI backtrace for cpu 1
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.15.0-rc2-next-20171208+ #63
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:trace_hardirqs_on_caller+0x347/0x5c0 kernel/locking/lockdep.c:2928
> RSP: 0018:ffff8801db307b38 EFLAGS: 00000806
> RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000001
> RDX: 1ffffffff0d3d899 RSI: 0000000080000001 RDI: ffffffff869ec4c8
> RBP: ffff8801db307b48 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff85400237
> R13: 1ffff1003b660fb1 R14: 0000000000000080 R15: dffffc0000000000
> FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000006dd000 CR3: 00000001ce2f2000 CR4: 00000000001406e0
> Call Trace:
>  <IRQ>
>  trace_hardirqs_on+0xd/0x10 kernel/locking/lockdep.c:2946
>  __do_softirq+0x237/0xbb2 kernel/softirq.c:269
>  invoke_softirq kernel/softirq.c:365 [inline]
>  irq_exit+0x1d3/0x210 kernel/softirq.c:405
>  scheduler_ipi+0x32a/0x830 kernel/sched/core.c:1804
>  smp_reschedule_interrupt+0xe6/0x670 arch/x86/kernel/smp.c:277
>  reschedule_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:944
>  </IRQ>
> RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
> RSP: 0018:ffff8801d9f97da8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02
> RAX: dffffc0000000000 RBX: 1ffff1003b3f2fb8 RCX: 0000000000000000
> RDX: 1ffffffff0c5975c RSI: 0000000000000001 RDI: ffffffff862cbae0
> RBP: ffff8801d9f97da8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
> R13: ffff8801d9f97e60 R14: ffffffff869efaa0 R15: 0000000000000000
>  arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline]
>  default_idle+0xbf/0x430 arch/x86/kernel/process.c:355
>  arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:346
>  default_idle_call+0x36/0x90 kernel/sched/idle.c:98
>  cpuidle_idle_call kernel/sched/idle.c:156 [inline]
>  do_idle+0x24a/0x3b0 kernel/sched/idle.c:246
>  cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:351
>  start_secondary+0x330/0x460 arch/x86/kernel/smpboot.c:277
>  secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237
> Code: 00 8b 3d 6d 7b 33 06 85 ff 0f 85 ea fd ff ff 48 c7 c7 c8 c4 9e 86 48
> b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 04 02 <48> 89 fa 83 e2
> 07 38 d0 7f 08 84 c0 0f 85 2d 02 00 00 80 3d 18


+loop maintainers

#syz dup: INFO: task hung in lo_ioctl


> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
> Please credit me with: Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
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