syzbot

INFO: task kworker/0:1:22 blocked for more than 140 seconds.
      Not tainted 4.14.91+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/0:1     D28656    22      2 0x80000000
Workqueue: events linkwatch_event
Call Trace:
 schedule+0x92/0x1c0 kernel/sched/core.c:3490
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
 __mutex_lock_common kernel/locking/mutex.c:833 [inline]
 __mutex_lock+0x559/0x1430 kernel/locking/mutex.c:893
 linkwatch_event+0xa/0x50 net/core/link_watch.c:236
 process_one_work+0x7c6/0x14e0 kernel/workqueue.c:2114
 worker_thread+0x5d7/0x1080 kernel/workqueue.c:2248
 kthread+0x310/0x420 kernel/kthread.c:232
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:402

Showing all locks held in the system:
3 locks held by kworker/0:1/22:
 #0:  ("events"){+.+.}, at: [<ffffffff86927d15>] process_one_work+0x6e5/0x14e0 kernel/workqueue.c:2085
 #1:  ((linkwatch_work).work){+.+.}, at: [<ffffffff86927d4b>] process_one_work+0x71b/0x14e0 kernel/workqueue.c:2089
 #2:  (rtnl_mutex){+.+.}, at: [<ffffffff87b5de1a>] linkwatch_event+0xa/0x50 net/core/link_watch.c:236
1 lock held by khungtaskd/23:
 #0:  (tasklist_lock){.+.+}, at: [<ffffffff869ff97c>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4541
3 locks held by kworker/1:1/68:
 #0:  ("%s"("ipv6_addrconf")){+.+.}, at: [<ffffffff86927d15>] process_one_work+0x6e5/0x14e0 kernel/workqueue.c:2085
 #1:  ((addr_chk_work).work){+.+.}, at: [<ffffffff86927d4b>] process_one_work+0x71b/0x14e0 kernel/workqueue.c:2089
 #2:  (rtnl_mutex){+.+.}, at: [<ffffffff87eca22a>] addrconf_verify_work+0xa/0x20 net/ipv6/addrconf.c:4430
2 locks held by getty/1746:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff87536982>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:275
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff87531da7>] n_tty_read+0x1f7/0x1700 drivers/tty/n_tty.c:2156

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 23 Comm: khungtaskd Not tainted 4.14.91+ #1
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x10e lib/dump_stack.c:53
 nmi_cpu_backtrace.cold+0x47/0x86 lib/nmi_backtrace.c:101
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff8804e402