INFO: task loop0:10577 blocked for more than 120 seconds. Not tainted 4.15.0-rc8+ #263 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. loop0 D24976 10577 2 0x80000000 Call Trace: context_switch kernel/sched/core.c:2799 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3375 schedule+0xf5/0x430 kernel/sched/core.c:3434 schedule_timeout+0x1a3/0x230 kernel/time/timer.c:1769 io_schedule_timeout+0x26/0x80 kernel/sched/core.c:5030 do_wait_for_common kernel/sched/completion.c:86 [inline] __wait_for_common kernel/sched/completion.c:107 [inline] wait_for_common_io kernel/sched/completion.c:124 [inline] wait_for_completion_io+0x415/0x770 kernel/sched/completion.c:172 submit_bio_wait+0x13f/0x1e0 block/bio.c:947 blkdev_issue_flush+0x226/0x310 block/blk-flush.c:548 blkdev_fsync+0x86/0xb0 fs/block_dev.c:632 vfs_fsync_range+0x110/0x260 fs/sync.c:196 vfs_fsync+0x29/0x30 fs/sync.c:210 lo_req_flush drivers/block/loop.c:444 [inline] do_req_filebacked drivers/block/loop.c:572 [inline] loop_handle_cmd drivers/block/loop.c:1724 [inline] loop_queue_work+0x12a2/0x3900 drivers/block/loop.c:1738 kthread_worker_fn+0x32b/0x980 kernel/kthread.c:642 loop_kthread_worker_fn+0x51/0x60 drivers/block/loop.c:841 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x37/0x50 arch/x86/entry/entry_64.S:530 Showing all locks held in the system: 2 locks held by khungtaskd/748: #0: (rcu_read_lock){....}, at: [<000000002f4cb971>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<000000002f4cb971>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<00000000962bc2e9>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4464 1 lock held by rsyslogd/3518: #0: (&f->f_pos_lock){+.+.}, at: [<00000000adc9c751>] __fdget_pos+0x12b/0x190 fs/file.c:770 2 locks held by getty/3641: #0: (&tty->ldisc_sem){++++}, at: [<0000000048075eaa>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000efc5384f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3642: #0: (&tty->ldisc_sem){++++}, at: [<0000000048075eaa>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000efc5384f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3643: #0: (&tty->ldisc_sem){++++}, at: [<0000000048075eaa>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000efc5384f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3644: #0: (&tty->ldisc_sem){++++}, at: [<0000000048075eaa>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000efc5384f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3645: #0: (&tty->ldisc_sem){++++}, at: [<0000000048075eaa>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000efc5384f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3646: #0: (&tty->ldisc_sem){++++}, at: [<0000000048075eaa>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000efc5384f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3647: #0: (&tty->ldisc_sem){++++}, at: [<0000000048075eaa>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000efc5384f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 1 lock held by syz-executor7/12888: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000eedfd24b>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor7/12914: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000eedfd24b>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 748 Comm: khungtaskd Not tainted 4.15.0-rc8+ #263 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+0x37/0x50 arch/x86/entry/entry_64.S:530 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54