INFO: task blkid:20189 blocked for more than 120 seconds. Not tainted 4.9.83-gda9fb78 #40 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. blkid D28272 20189 2224 0x00000006 ffff8801b7f78000 ffff8801c38eb480 ffff8801c637ea00 ffff8801c2eb6000 ffff8801db221b98 ffff8801b7fc76f8 ffffffff838a3e1b 0000000000000001 0000000000000007 00ff8801b7f78000 ffff8801db222468 ffff8801db222490 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3550 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3583 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621 [] lo_release+0x1f/0x160 drivers/block/loop.c:1590 [] __blkdev_put+0x5f7/0x7e0 fs/block_dev.c:1598 [] blkdev_put+0x85/0x550 fs/block_dev.c:1663 [] blkdev_close+0x8b/0xb0 fs/block_dev.c:1670 [] __fput+0x28c/0x6e0 fs/file_table.c:208 [] ____fput+0x15/0x20 fs/file_table.c:244 [] task_work_run+0x115/0x190 kernel/task_work.c:116 [] exit_task_work include/linux/task_work.h:21 [inline] [] do_exit+0x7e7/0x2a40 kernel/exit.c:833 [] do_group_exit+0x108/0x320 kernel/exit.c:937 [] get_signal+0x4d4/0x14e0 kernel/signal.c:2317 [] do_signal+0x87/0x19f0 arch/x86/kernel/signal.c:807 [] exit_to_usermode_loop+0xe1/0x120 arch/x86/entry/common.c:157 [] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline] [] syscall_return_slowpath arch/x86/entry/common.c:260 [inline] [] do_syscall_64+0x36f/0x490 arch/x86/entry/common.c:287 [] entry_SYSCALL_64_after_swapgs+0x47/0xc5 Showing all locks held in the system: 2 locks held by khungtaskd/514: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x125/0xa70 kernel/hung_task.c:239 #1: (tasklist_lock){.+.?..}, at: [] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336 2 locks held by getty/3664: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133 2 locks held by blkid/20189: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_put+0xbc/0x7e0 fs/block_dev.c:1579 #1: (loop_index_mutex){+.+.+.}, at: [] lo_release+0x1f/0x160 drivers/block/loop.c:1590 1 lock held by syz-executor2/23126: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 2 locks held by syz-executor4/23137: #0: (loop_index_mutex){+.+.+.}, at: [] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1899 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [] loop_control_ioctl+0x176/0x300 drivers/block/loop.c:1913 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.83-gda9fb78 #40 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d86afd00 ffffffff81d95149 0000000000000000 0000000000000000 0000000000000000 0000000000000001 ffffffff810bb190 ffff8801d86afd38 ffffffff81da026d 0000000000000000 0000000000000000 ffff8801b7f78418 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60 [] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x6f0/0xa70 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:361 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff838b3b06