unregister_netdevice: waiting for lo to become free. Usage count = 6 INFO: task blkid:21012 blocked for more than 120 seconds. Not tainted 4.15.0+ #298 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. blkid D20416 21012 4090 0x80000006 Call Trace: context_switch kernel/sched/core.c:2845 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3421 schedule+0xf5/0x430 kernel/sched/core.c:3480 io_schedule+0x1c/0x70 kernel/sched/core.c:5096 wait_on_page_bit_common mm/filemap.c:1099 [inline] __lock_page+0x574/0x720 mm/filemap.c:1272 lock_page include/linux/pagemap.h:483 [inline] truncate_inode_pages_range+0x197c/0x1fe0 mm/truncate.c:448 truncate_inode_pages+0x24/0x30 mm/truncate.c:478 kill_bdev+0xbc/0xf0 fs/block_dev.c:86 __blkdev_put+0x198/0x7f0 fs/block_dev.c:1764 blkdev_put+0x85/0x4f0 fs/block_dev.c:1835 blkdev_close+0x8b/0xb0 fs/block_dev.c:1842 __fput+0x327/0x7e0 fs/file_table.c:209 ____fput+0x15/0x20 fs/file_table.c:243 task_work_run+0x199/0x270 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x9bb/0x1ad0 kernel/exit.c:865 do_group_exit+0x149/0x400 kernel/exit.c:968 get_signal+0x73a/0x16d0 kernel/signal.c:2469 do_signal+0x90/0x1e90 arch/x86/kernel/signal.c:809 exit_to_usermode_loop+0x258/0x2f0 arch/x86/entry/common.c:162 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline] syscall_return_slowpath arch/x86/entry/common.c:265 [inline] do_syscall_64+0x6ed/0x940 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x26/0x9b RIP: 0033:0x7f115d271310 RSP: 002b:00007ffc7673d768 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: fffffffffffffffc RBX: 0000000000000000 RCX: 00007f115d271310 RDX: 0000000000000400 RSI: 0000000001142c58 RDI: 0000000000000003 RBP: 0000000001142c30 R08: 0000000000000028 R09: 0000000001680000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000001142030 R13: 0000000000000400 R14: 0000000001142080 R15: 0000000001142c48 Showing all locks held in the system: 4 locks held by kworker/u4:0/5: #0: ((wq_completion)"%s""netns"){+.+.}, at: [<00000000efc9edfd>] process_one_work+0xaaf/0x1af0 kernel/workqueue.c:2084 #1: (net_cleanup_work){+.+.}, at: [<000000003e5e78ce>] process_one_work+0xb01/0x1af0 kernel/workqueue.c:2088 #2: (net_mutex){+.+.}, at: [<0000000098304a9c>] cleanup_net+0x242/0xcc0 net/core/net_namespace.c:484 #3: (rcu_sched_state.barrier_mutex){+.+.}, at: [<00000000267e6427>] _rcu_barrier+0x142/0x750 kernel/rcu/tree.c:3517 2 locks held by khungtaskd/757: #0: (rcu_read_lock){....}, at: [<00000000549bcad3>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000549bcad3>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<00000000e5d9a0e7>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 2 locks held by getty/4082: #0: (&tty->ldisc_sem){++++}, at: [<00000000871bb47b>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000d38eada2>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4083: #0: (&tty->ldisc_sem){++++}, at: [<00000000871bb47b>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000d38eada2>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4084: #0: (&tty->ldisc_sem){++++}, at: [<00000000871bb47b>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000d38eada2>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4085: #0: (&tty->ldisc_sem){++++}, at: [<00000000871bb47b>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000d38eada2>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4086: #0: (&tty->ldisc_sem){++++}, at: [<00000000871bb47b>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000d38eada2>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4087: #0: (&tty->ldisc_sem){++++}, at: [<00000000871bb47b>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000d38eada2>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4088: #0: (&tty->ldisc_sem){++++}, at: [<00000000871bb47b>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000d38eada2>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 1 lock held by blkid/21012: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000091dc871>] __blkdev_put+0xbc/0x7f0 fs/block_dev.c:1757 1 lock held by syz-executor7/2285: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000c6313a68>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:2145 1 lock held by syz-executor7/2293: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000c6313a68>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:2145 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 757 Comm: khungtaskd Not tainted 4.15.0+ #298 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+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:429 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54