INFO: task systemd-shutdow:1 blocked for more than 143 seconds. Not tainted 5.6.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. systemd-shutdow D24736 1 0 0x00004000 Call Trace: schedule+0xcd/0x2b0 kernel/sched/core.c:4154 wait_for_device_probe+0x11e/0x180 drivers/base/dd.c:688 device_shutdown+0x18/0x5c0 drivers/base/core.c:3481 kernel_restart+0x11/0x30 kernel/reboot.c:246 __do_sys_reboot+0x31e/0x3e0 kernel/reboot.c:347 do_syscall_64+0xb6/0x5a0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f1fa71458c6 Code: 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 63 d7 be 69 19 12 28 48 c7 c7 ad de e1 fe b8 a9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 02 f3 c3 48 8b 15 a1 75 2b 00 f7 d8 64 89 02 RSP: 002b:00007fff56717558 EFLAGS: 00000202 ORIG_RAX: 00000000000000a9 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1fa71458c6 RDX: 0000000001234567 RSI: 0000000028121969 RDI: fffffffffee1dead RBP: 00007fff567175e8 R08: 00000000000000a0 R09: 0000000000000005 R10: 0000000000000002 R11: 0000000000000202 R12: 0000000000000000 R13: 0000000000000000 R14: 00005558be53f150 R15: 00007fff567178d8 Showing all locks held in the system: 1 lock held by systemd-shutdow/1: #0: ffffffff870e0d40 (system_transition_mutex){+.+.}, at: __do_sys_reboot+0x1a3/0x3e0 kernel/reboot.c:344 1 lock held by khungtaskd/23: #0: ffffffff87109060 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x264 kernel/locking/lockdep.c:5331 5 locks held by kworker/0:4/3093: #0: ffff8881d8cbe928 ((wq_completion)usb_hub_wq){+.+.}, at: __write_once_size include/linux/compiler.h:226 [inline] #0: ffff8881d8cbe928 ((wq_completion)usb_hub_wq){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff8881d8cbe928 ((wq_completion)usb_hub_wq){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:855 [inline] #0: ffff8881d8cbe928 ((wq_completion)usb_hub_wq){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:40 [inline] #0: ffff8881d8cbe928 ((wq_completion)usb_hub_wq){+.+.}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff8881d8cbe928 ((wq_completion)usb_hub_wq){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline] #0: ffff8881d8cbe928 ((wq_completion)usb_hub_wq){+.+.}, at: process_one_work+0x82a/0x1620 kernel/workqueue.c:2235 #1: ffff8881c7c5fdd0 ((work_completion)(&hub->events)){+.+.}, at: process_one_work+0x85e/0x1620 kernel/workqueue.c:2239 #2: ffff8881d4959200 (&dev->mutex){....}, at: device_lock include/linux/device.h:771 [inline] #2: ffff8881d4959200 (&dev->mutex){....}, at: hub_event+0x1be/0x4300 drivers/usb/core/hub.c:5509 #3: ffff8881d9952200 (&dev->mutex){....}, at: device_lock include/linux/device.h:771 [inline] #3: ffff8881d9952200 (&dev->mutex){....}, at: __device_attach+0x7b/0x390 drivers/base/dd.c:874 #4: ffff8881c8797190 (&dev->mutex){....}, at: device_lock include/linux/device.h:771 [inline] #4: ffff8881c8797190 (&dev->mutex){....}, at: __device_attach+0x7b/0x390 drivers/base/dd.c:874 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 23 Comm: khungtaskd Not tainted 5.6.0-rc5-syzkaller #0 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+0xef/0x16e lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1db/0x207 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline] watchdog+0xa99/0xfd0 kernel/hung_task.c:289 kthread+0x318/0x420 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline] NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline] NMI backtrace for cpu 0 skipped: idling at default_idle+0x28/0x300 arch/x86/kernel/process.c:695