INFO: task kworker/1:4:5301 blocked for more than 120 seconds. Not tainted 4.16.0+ #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:4 D23928 5301 2 0x80000000 Workqueue: events cgwb_release_workfn Call Trace: context_switch kernel/sched/core.c:2848 [inline] __schedule+0x801/0x1e30 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: 000000002fdad2e0 (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: 000000002fdad2e0 (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249 #1: 000000001631ce1e (tasklist_lock){.+.+}, at: debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470 2 locks held by getty/4474: #0: 000000003b131917 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000008e41ed06 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4475: #0: 000000004972ff82 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000093fb25c4 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4476: #0: 0000000004980e91 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000005bdc5e50 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4477: #0: 00000000e94e4bed (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000865f9e3a (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4478: #0: 000000008f3911ee (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000f121f27b (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4479: #0: 00000000eacb0c39 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000090454be3 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4480: #0: 000000009ed63524 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000016540ad8 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by kworker/1:4/5301: #0: 00000000a8b395c1 ((wq_completion)"events"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline] #0: 00000000a8b395c1 ((wq_completion)"events"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 00000000a8b395c1 ((wq_completion)"events"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 00000000a8b395c1 ((wq_completion)"events"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline] #0: 00000000a8b395c1 ((wq_completion)"events"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 00000000a8b395c1 ((wq_completion)"events"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 00000000a8b395c1 ((wq_completion)"events"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116 #1: 00000000ad62cc5d ((work_completion)(&wb->release_work)){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120 1 lock held by syz-executor0/17073: #0: 00000000f2b927b2 (event_mutex){+.+.}, at: perf_trace_destroy+0x28/0x100 kernel/trace/trace_event_perf.c:235 3 locks held by syz-executor4/17085: #0: 00000000708edc47 (&sig->cred_guard_mutex){+.+.}, at: SYSC_perf_event_open+0x129f/0x2fa0 kernel/events/core.c:10457 #1: 000000009b574043 (&pmus_srcu){....}, at: perf_event_alloc.part.91+0x103c/0x30a0 kernel/events/core.c:10018 #2: 00000000f2b927b2 (event_mutex){+.+.}, at: perf_trace_init+0x50/0x250 kernel/trace/trace_event_perf.c:217 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 888 Comm: khungtaskd Not tainted 4.16.0+ #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_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 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 4552 Comm: syz-executor6 Not tainted 4.16.0+ #1 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:do_wait+0x1c2/0xb60 kernel/exit.c:1505 RSP: 0018:ffff880191c9fa10 EFLAGS: 00000286 RAX: ffff880191c9fc58 RBX: ffff880191c90440 RCX: 0000000000000000 RDX: 1ffffffff11630ed RSI: 0000000000000001 RDI: 0000000000000282 RBP: ffff880191c9fbc8 R08: ffffed003b0a69bd R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000 R13: ffff880191c9fc08 R14: 0000000000000000 R15: ffff880191c9fc08 FS: 0000000000e9f940(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b9bc22000 CR3: 0000000191c69000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: kernel_wait4+0x23f/0x3d0 kernel/exit.c:1665 SYSC_wait4+0x119/0x120 kernel/exit.c:1677 SyS_wait4+0x2c/0x40 kernel/exit.c:1673 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x40f61a RSP: 002b:0000000000a3eab8 EFLAGS: 00000246 ORIG_RAX: 000000000000003d RAX: ffffffffffffffda RBX: 000000000000014d RCX: 000000000040f61a RDX: 0000000040000001 RSI: 0000000000a3ead4 RDI: ffffffffffffffff RBP: 000000000003c66f R08: 0000000000000001 R09: 0000000000e9f940 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000003 R14: 00000000000004fa R15: 000000000003c661 Code: 8b bb b8 06 00 00 48 8b b5 58 fe ff ff 49 bc 00 00 00 00 00 fc ff df 48 83 c7 20 e8 19 ae 12 00 49 8d 45 50 48 89 85 60 fe ff ff <48> 8d 85 18 ff ff ff 48 89 85 48 fe ff ff 48 c1 e8 03 4c 01 e0