INFO: task systemd-shutdow:1 blocked for more than 143 seconds. Not tainted 5.6.0-rc7-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. systemd-shutdow D24576 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: 0033:0x7f5d990ed8c6 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:00007ffcb91ee6c8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a9 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f5d990ed8c6 RDX: 0000000001234567 RSI: 0000000028121969 RDI: fffffffffee1dead RBP: 00007ffcb91ee758 R08: 0000000000000028 R09: 0000000000000005 R10: 0000000000000002 R11: 0000000000000202 R12: 0000000000000000 R13: 0000000000000000 R14: 0000560c68543150 R15: 00007ffcb91eea48 Showing all locks held in the system: 1 lock held by systemd-shutdow/1: #0: ffffffff870e0840 (system_transition_mutex){+.+.}, at: __do_sys_reboot+0x1a3/0x3e0 kernel/reboot.c:344 1 lock held by khungtaskd/23: #0: ffffffff87108b60 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x264 kernel/locking/lockdep.c:5331 6 locks held by kworker/0:4/3118: #0: ffff8881d8d8b928 ((wq_completion)usb_hub_wq){+.+.}, at: __write_once_size include/linux/compiler.h:226 [inline] #0: ffff8881d8d8b928 ((wq_completion)usb_hub_wq){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff8881d8d8b928 ((wq_completion)usb_hub_wq){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:855 [inline] #0: ffff8881d8d8b928 ((wq_completion)usb_hub_wq){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:40 [inline] #0: ffff8881d8d8b928 ((wq_completion)usb_hub_wq){+.+.}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff8881d8d8b928 ((wq_completion)usb_hub_wq){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline] #0: ffff8881d8d8b928 ((wq_completion)usb_hub_wq){+.+.}, at: process_one_work+0x82a/0x1620 kernel/workqueue.c:2237 #1: ffff8881d24f7dd0 ((work_completion)(&hub->events)){+.+.}, at: process_one_work+0x85e/0x1620 kernel/workqueue.c:2241 #2: ffff8881d4ca2200 (&dev->mutex){....}, at: device_lock include/linux/device.h:771 [inline] #2: ffff8881d4ca2200 (&dev->mutex){....}, at: hub_event+0x1be/0x4300 drivers/usb/core/hub.c:5509 #3: ffff8881c6479200 (&dev->mutex){....}, at: device_lock include/linux/device.h:771 [inline] #3: ffff8881c6479200 (&dev->mutex){....}, at: __device_attach+0x7b/0x390 drivers/base/dd.c:874 #4: ffff8881cd297190 (&dev->mutex){....}, at: device_lock include/linux/device.h:771 [inline] #4: ffff8881cd297190 (&dev->mutex){....}, at: __device_attach+0x7b/0x390 drivers/base/dd.c:874 #5: ffff8881c6650bd0 (&dev->phy_mutex){+.+.}, at: asix_mdio_read+0x98/0x2d0 drivers/net/usb/asix_common.c:452 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 23 Comm: khungtaskd Not tainted 5.6.0-rc7-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 CPU: 0 PID: 3118 Comm: kworker/0:4 Not tainted 5.6.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: usb_hub_wq hub_event RIP: 0010:io_serial_in+0x60/0x80 drivers/tty/serial/8250/8250_port.c:447 Code: 0f b6 8d e9 00 00 00 48 8d 7d 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 13 03 5d 38 89 da ec <5b> 0f b6 c0 5d c3 e8 c5 c2 49 ff eb c9 e8 ee c2 49 ff eb e6 66 90 RSP: 0018:ffff8881d24f6a08 EFLAGS: 00000002 RAX: dffffc0000000060 RBX: 00000000000003fd RCX: 0000000000000000 RDX: 00000000000003fd RSI: ffffffff821e5e5c RDI: ffffffff89ff5b78 RBP: ffffffff89ff5b40 R08: ffff8881d58fb100 R09: ffffed103a49ed47 R10: ffffed103a49ed46 R11: 0000000000000003 R12: 0000000000000020 R13: fffffbfff13febb7 R14: fffffbfff13feb71 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f5d996d9730 CR3: 00000001ce1c5000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: serial_in drivers/tty/serial/8250/8250.h:113 [inline] wait_for_xmitr+0x9a/0x210 drivers/tty/serial/8250/8250_port.c:1968 serial8250_console_putchar+0x1b/0x50 drivers/tty/serial/8250/8250_port.c:3100 uart_console_write+0x59/0x100 drivers/tty/serial/serial_core.c:1928 serial8250_console_write+0x2f8/0x880 drivers/tty/serial/8250/8250_port.c:3164 call_console_drivers kernel/printk/printk.c:1791 [inline] console_unlock+0x8be/0xca0 kernel/printk/printk.c:2473 vprintk_emit+0x171/0x3d0 kernel/printk/printk.c:1996 dev_vprintk_emit+0x4fc/0x541 drivers/base/core.c:3616 dev_printk_emit+0xba/0xf1 drivers/base/core.c:3627 __netdev_printk net/core/dev.c:10279 [inline] __netdev_printk+0x1c6/0x27c net/core/dev.c:10275 netdev_warn+0xd7/0x109 net/core/dev.c:10332 asix_write_cmd.cold+0x3a/0x46 drivers/net/usb/asix_common.c:52 asix_set_sw_mii+0x27/0x50 drivers/net/usb/asix_common.c:275 asix_mdio_read+0xc6/0x2d0 drivers/net/usb/asix_common.c:454 asix_phy_reset.isra.0+0x109/0x170 drivers/net/usb/asix_devices.c:215 ax88172_bind+0x41a/0x5d6 drivers/net/usb/asix_devices.c:272 usbnet_probe+0xb54/0x2570 drivers/net/usb/usbnet.c:1737 usb_probe_interface+0x310/0x800 drivers/usb/core/driver.c:374 really_probe+0x290/0xac0 drivers/base/dd.c:551 driver_probe_device+0x223/0x350 drivers/base/dd.c:724 __device_attach_driver+0x1d1/0x290 drivers/base/dd.c:831 bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:431 __device_attach+0x217/0x390 drivers/base/dd.c:897 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491 device_add+0x1459/0x1bf0 drivers/base/core.c:2500 usb_set_configuration+0xece/0x1840 drivers/usb/core/message.c:2025 usb_generic_driver_probe+0x9d/0xe0 drivers/usb/core/generic.c:241 usb_probe_device+0xd9/0x230 drivers/usb/core/driver.c:272 really_probe+0x290/0xac0 drivers/base/dd.c:551 driver_probe_device+0x223/0x350 drivers/base/dd.c:724 __device_attach_driver+0x1d1/0x290 drivers/base/dd.c:831 bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:431 __device_attach+0x217/0x390 drivers/base/dd.c:897 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491 device_add+0x1459/0x1bf0 drivers/base/core.c:2500 usb_new_device.cold+0x540/0xcd0 drivers/usb/core/hub.c:2548 hub_port_connect drivers/usb/core/hub.c:5195 [inline] hub_port_connect_change drivers/usb/core/hub.c:5335 [inline] port_event drivers/usb/core/hub.c:5481 [inline] hub_event+0x21cb/0x4300 drivers/usb/core/hub.c:5563 process_one_work+0x94b/0x1620 kernel/workqueue.c:2266 worker_thread+0x96/0xe20 kernel/workqueue.c:2412 kthread+0x318/0x420 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352