kworker/dying (6) used greatest stack depth: 12392 bytes left INFO: task kworker/u4:5:9043 blocked for more than 120 seconds. Not tainted 4.17.0+ #82 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:5 D15624 9043 2 0x80000000 Workqueue: writeback wb_workfn (flush-7:0) Call Trace: context_switch kernel/sched/core.c:2876 [inline] __schedule+0x801/0x1e30 kernel/sched/core.c:3518 schedule+0xef/0x430 kernel/sched/core.c:3562 blk_queue_enter+0x8da/0xdf0 block/blk-core.c:953 generic_make_request+0x144/0x1510 block/blk-core.c:2395 submit_bio+0xba/0x460 block/blk-core.c:2568 submit_bh_wbc+0x5e8/0x7c0 fs/buffer.c:3076 __block_write_full_page+0x82e/0xef0 fs/buffer.c:1758 block_write_full_page+0x1ff/0x250 fs/buffer.c:2944 blkdev_writepage+0x24/0x30 fs/block_dev.c:566 __writepage+0x69/0xe0 mm/page-writeback.c:2302 write_cache_pages+0x920/0x1690 mm/page-writeback.c:2240 generic_writepages+0xcc/0x120 mm/page-writeback.c:2326 blkdev_writepages+0x1d/0x30 fs/block_dev.c:1951 do_writepages+0x9a/0x1a0 mm/page-writeback.c:2341 __writeback_single_inode+0x1e4/0x15c0 fs/fs-writeback.c:1323 writeback_sb_inodes+0x6f0/0x11a0 fs/fs-writeback.c:1587 __writeback_inodes_wb+0x1b0/0x320 fs/fs-writeback.c:1656 wb_writeback+0x9e4/0xf50 fs/fs-writeback.c:1765 wb_check_background_flush fs/fs-writeback.c:1833 [inline] wb_do_writeback fs/fs-writeback.c:1921 [inline] wb_workfn+0xd08/0x1740 fs/fs-writeback.c:1949 process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145 worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 Showing all locks held in the system: 2 locks held by khungtaskd/891: #0: 000000001a4dea98 (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: 000000001a4dea98 (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249 #1: 00000000094c9ab0 (tasklist_lock){.+.+}, at: debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470 1 lock held by rsyslogd/4369: #0: 00000000789deb6f (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1a9/0x1e0 fs/file.c:766 2 locks held by getty/4459: #0: 000000001907aaad (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000008c5a3edb (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4460: #0: 0000000055d6aaf4 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000f6410704 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4461: #0: 00000000fb6c6740 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000098781d11 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4462: #0: 000000003afa7150 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000095c398fa (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4463: #0: 00000000d9c35df1 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000c673eb7d (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4464: #0: 000000005e8cf9ca (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000034add686 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4465: #0: 00000000be656621 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000f0c85883 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 1 lock held by syz-executor0/4536: #0: 000000008f6b13d2 (&lo->lo_ctl_mutex/1){+.+.}, at: lo_ioctl+0x8d/0x2130 drivers/block/loop.c:1392 3 locks held by kworker/u4:5/9043: #0: 0000000040254db0 ((wq_completion)"writeback"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline] #0: 0000000040254db0 ((wq_completion)"writeback"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 0000000040254db0 ((wq_completion)"writeback"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 0000000040254db0 ((wq_completion)"writeback"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline] #0: 0000000040254db0 ((wq_completion)"writeback"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 0000000040254db0 ((wq_completion)"writeback"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 0000000040254db0 ((wq_completion)"writeback"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116 #1: 000000003ff85283 ((work_completion)(&(&wb->dwork)->work)){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120 #2: 00000000c19687f4 (&type->s_umount_key#35){.+.+}, at: trylock_super+0x22/0x110 fs/super.c:409 1 lock held by syz-executor4/19276: #0: 000000008f6b13d2 (&lo->lo_ctl_mutex/1){+.+.}, at: lo_ioctl+0x8d/0x2130 drivers/block/loop.c:1392 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 891 Comm: khungtaskd Not tainted 4.17.0+ #82 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1b9/0x294 lib/dump_stack.c:113 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x151/0x192 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+0xc10/0xf60 kernel/hung_task.c:249 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 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