INFO: task kworker/1:2:1974 blocked for more than 120 seconds. Not tainted 4.16.0+ #19 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:2 D20536 1974 2 0x80000000 Workqueue: events cgwb_release_workfn Call Trace: context_switch kernel/sched/core.c:2848 [inline] __schedule+0x807/0x1e40 kernel/sched/core.c:3490 schedule+0xef/0x430 kernel/sched/core.c:3549 bit_wait+0x18/0x90 kernel/sched/wait_bit.c:197 __wait_on_bit+0xb3/0x130 kernel/sched/wait_bit.c:48 out_of_line_wait_on_bit+0x204/0x3a0 kernel/sched/wait_bit.c:63 wait_on_bit include/linux/wait_bit.h:76 [inline] wb_shutdown+0x370/0x470 mm/backing-dev.c:366 cgwb_release_workfn+0x87/0x750 mm/backing-dev.c:509 process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145 worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279 kthread+0x345/0x410 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411 Showing all locks held in the system: 2 locks held by khungtaskd/888: #0: 00000000047d2c6b (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: 00000000047d2c6b (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249 #1: 00000000eb6fee50 (tasklist_lock){.+.+}, at: debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470 2 locks held by kworker/1:2/1974: #0: 00000000298cd8a8 ((wq_completion)"events"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline] #0: 00000000298cd8a8 ((wq_completion)"events"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 00000000298cd8a8 ((wq_completion)"events"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 00000000298cd8a8 ((wq_completion)"events"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline] #0: 00000000298cd8a8 ((wq_completion)"events"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 00000000298cd8a8 ((wq_completion)"events"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 00000000298cd8a8 ((wq_completion)"events"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116 #1: 00000000e1229221 ((work_completion)(&wb->release_work)){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120 2 locks held by getty/4400: #0: 00000000089a20f8 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000002a27da8b (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4401: #0: 00000000fa5f5e26 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000080d465f1 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4402: #0: 00000000d85e959a (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000008f5d8c5 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4403: #0: 00000000c7c6e90b (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000d80c996b (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4404: #0: 00000000043a0046 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000dce7e7de (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4405: #0: 00000000cff4ddb8 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000d3d61b63 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4406: #0: 00000000b08f4d67 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000c63474ca (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 888 Comm: khungtaskd Not tainted 4.16.0+ #19 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 FAULT_FLAG_ALLOW_RETRY missing 30 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:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411 CPU: 1 PID: 15912 Comm: syz-executor0 Not tainted 4.16.0+ #19 Sending NMI from CPU 0 to CPUs 1: 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 backtrace for cpu 1 CPU: 1 PID: 15912 Comm: syz-executor0 Not tainted 4.16.0+ #19 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:inb arch/x86/include/asm/io.h:333 [inline] RIP: 0010:io_serial_in+0x6b/0x90 drivers/tty/serial/8250/8250_port.c:447 RSP: 0018:ffff88018c56ea58 EFLAGS: 00000002 RAX: dffffc0000000060 RBX: 00000000000003fd RCX: 0000000000000000 RDX: 00000000000003fd RSI: ffffffff83823ca1 RDI: ffffffff8ae8a4b8 RBP: ffff88018c56ea68 R08: ffff8801c82f4040 R09: fffffbfff15d1490 R10: fffffbfff15d1490 R11: ffffffff8ae8a483 R12: ffffffff8ae8a480 R13: 0000000000000020 R14: 000000000000005b R15: fffffbfff15d1499 FS: 00007f7e76564700(0000) GS:ffff8801db100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f41e609b000 CR3: 00000001b162b000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: serial_in drivers/tty/serial/8250/8250.h:111 [inline] wait_for_xmitr+0xa7/0x250 drivers/tty/serial/8250/8250_port.c:2026 serial8250_console_putchar+0x1f/0x60 drivers/tty/serial/8250/8250_port.c:3178 uart_console_write+0x50/0x110 drivers/tty/serial/serial_core.c:1864 serial8250_console_write+0x70c/0xb00 drivers/tty/serial/8250/8250_port.c:3244 univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:590 call_console_drivers kernel/printk/printk.c:1718 [inline] console_unlock+0xac2/0x1100 kernel/printk/printk.c:2395 vprintk_emit+0x6ad/0xdd0 kernel/printk/printk.c:1907 vprintk_default+0x28/0x30 kernel/printk/printk.c:1947 vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:379 printk+0x9e/0xba kernel/printk/printk.c:1980 printk_stack_address arch/x86/kernel/dumpstack.c:69 [inline] show_trace_log_lvl+0x21e/0x25c arch/x86/kernel/dumpstack.c:201 show_stack+0x38/0x3a arch/x86/kernel/dumpstack.c:236 __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1b9/0x294 lib/dump_stack.c:113 handle_userfault.cold.32+0x44/0x57 fs/userfaultfd.c:430 do_anonymous_page mm/memory.c:3147 [inline] handle_pte_fault mm/memory.c:3961 [inline] __handle_mm_fault+0x34be/0x4150 mm/memory.c:4087 handle_mm_fault+0x53a/0xc70 mm/memory.c:4124 __do_page_fault+0x60b/0xe40 arch/x86/mm/fault.c:1399 do_page_fault+0xee/0x8a7 arch/x86/mm/fault.c:1474 page_fault+0x25/0x50 arch/x86/entry/entry_64.S:1159 RIP: 0010:copy_user_generic_unrolled+0x86/0xc0 arch/x86/lib/copy_user_64.S:65 RSP: 0018:ffff88018c56fce8 EFLAGS: 00010206 RAX: ffffed00318adfae RBX: 0000000000000018 RCX: 0000000000000003 RDX: 0000000000000000 RSI: 0000000020013000 RDI: ffff88018c56fd58 RBP: ffff88018c56fd20 R08: ffffed00318adfae R09: ffffed00318adfab R10: ffffed00318adfad R11: ffff88018c56fd6f R12: 0000000020013018 R13: 0000000020013000 R14: ffff88018c56fd58 R15: 00007ffffffff000 copy_from_user include/linux/uaccess.h:147 [inline] SYSC_sigaltstack kernel/signal.c:3539 [inline] SyS_sigaltstack+0xae/0x320 kernel/signal.c:3535 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x455279 RSP: 002b:00007f7e76563c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000083 RAX: ffffffffffffffda RBX: 00007f7e765646d4 RCX: 0000000000455279 RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000020013000 RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000609 R14: 00000000006fc178 R15: 0000000000000000 Code: 24 d1 00 00 00 49 8d 7c 24 38 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 d3 e3 80 3c 02 00 75 17 41 03 5c 24 38 89 da ec <5b> 0f b6 c0 41 5c 5d c3 e8 98 8b 30 fe eb c2 e8 f1 8b 30 fe eb