rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1):
 P28/1:b..l

rcu: 	(detected by 0, t=10502 jiffies, g=73645, q=1326 ncpus=2)
task:kworker/1:1     state:R
  running task    
 stack:20600 pid:28    tgid:28    ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: usb_hub_wq hub_event

Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x1325/0x47d0 kernel/sched/core.c:7234
 preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7556
 irqentry_exit_to_kernel_mode_preempt include/linux/irq-entry-common.h:468 [inline]
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
 irqentry_exit+0x1da/0x7b0 kernel/entry/common.c:167
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:lock_acquire+0x5e/0x370 kernel/locking/lockdep.c:5872
Code: 05 3b 75 6e 0b 83 f8 07 0f 87 da 00 00 00 48 0f a3 05 c6 84 63 09 0f 82 ac 02 00 00 8b 35 8e 94 63 09 85 f6 0f 85 c7 00 00 00 <48> 8b 44 24 30 65 48 2b 05 dd 74 6e 0b 0f 85 ec 02 00 00 48 83 c4
RSP: 0018:ffffc900001e6858 EFLAGS: 00000206

RAX: 0000000000000046 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff890d1b7d RDI: ffffffff87b15480
RBP: ffffffff896e2b40 R08: 00000000221c4552 R09: 0000000000000007
R10: 0000000000000200 R11: 0000000000000000 R12: 0000000000000002
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 rcu_read_lock include/linux/rcupdate.h:840 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1183 [inline]
 kernfs_root+0x34/0x2a0 fs/kernfs/kernfs-internal.h:76
 kernfs_active+0x5c/0x110 fs/kernfs/dir.c:40
 kernfs_activate_one+0x99/0x290 fs/kernfs/dir.c:1435
 kernfs_activate fs/kernfs/dir.c:1466 [inline]
 kernfs_add_one+0x5ec/0xaa0 fs/kernfs/dir.c:868
 __kernfs_create_file+0x295/0x350 fs/kernfs/file.c:1079
 sysfs_add_file_mode_ns+0x207/0x3c0 fs/sysfs/file.c:316
 sysfs_merge_group+0x194/0x340 fs/sysfs/group.c:382
 dpm_sysfs_add+0x237/0x280 drivers/base/power/sysfs.c:704
 device_add+0x9f4/0x1970 drivers/base/core.c:3717
 cdev_device_add+0x12b/0x270 fs/char_dev.c:553
 evdev_connect+0x3a8/0x4b0 drivers/input/evdev.c:1383
 input_attach_handler.isra.0+0x177/0x1e0 drivers/input/input.c:1011
 input_register_device.cold+0x139/0x375 drivers/input/input.c:2398
 snd_usb_caiaq_input_init+0xf78/0x1b00 sound/usb/caiaq/input.c:836
 setup_card+0x301/0x9d0 sound/usb/caiaq/device.c:379
 init_card sound/usb/caiaq/device.c:526 [inline]
 snd_probe+0xbe6/0x1270 sound/usb/caiaq/device.c:550
 usb_probe_interface+0x386/0x9b0 drivers/usb/core/driver.c:399
 call_driver_probe drivers/base/dd.c:628 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:706
 __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
 driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
 __device_attach_driver+0x1df/0x320 drivers/base/dd.c:1026
 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1098
 device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x64/0x160 drivers/base/bus.c:620
 device_add+0x121d/0x1970 drivers/base/core.c:3772
 usb_set_configuration+0xd97/0x1c60 drivers/usb/core/message.c:2268
 usb_generic_driver_probe+0xa1/0xe0 drivers/usb/core/generic.c:250
 usb_probe_device+0xef/0x400 drivers/usb/core/driver.c:293
 call_driver_probe drivers/base/dd.c:628 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:706
 __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
 driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
 __device_attach_driver+0x1df/0x320 drivers/base/dd.c:1026
 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1098
 device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x64/0x160 drivers/base/bus.c:620
 device_add+0x121d/0x1970 drivers/base/core.c:3772
 usb_new_device.cold+0x685/0x115c drivers/usb/core/hub.c:2700
 hub_port_connect drivers/usb/core/hub.c:5572 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5712 [inline]
 port_event drivers/usb/core/hub.c:5876 [inline]
 hub_event+0x314d/0x4af0 drivers/usb/core/hub.c:5958
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x69a/0xc80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>