BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 184s!
Showing busy workqueues and worker pools:
workqueue events_long: flags=0x0
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
    pending: gc_worker

======================================================
WARNING: possible circular locking dependency detected
4.14.133+ #17 Not tainted
------------------------------------------------------
swapper/0/0 is trying to acquire lock:
 (console_owner){-.-.}, at: [<00000000298da86d>] log_next /kernel/printk/printk.c:492 [inline]
 (console_owner){-.-.}, at: [<00000000298da86d>] console_unlock+0x28e/0xc70 /kernel/printk/printk.c:2378

but task is already holding lock:
 (&(&pool->lock)->rlock){-.-.}, at: [<000000005cae8eab>] show_workqueue_state /kernel/workqueue.c:4518 [inline]
 (&(&pool->lock)->rlock){-.-.}, at: [<000000005cae8eab>] show_workqueue_state.cold+0x22f/0xeb3 /kernel/workqueue.c:4491

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&(&pool->lock)->rlock){-.-.}:

-> #3 (&pool->lock/1){..-.}:

-> #2 (&(&port->lock)->rlock){-.-.}:

-> #1 (&port_lock_key){-.-.}:

-> #0 (console_owner){-.-.}:

other info that might help us debug this:

Chain exists of:
  console_owner --> &pool->lock/1 --> &(&pool->lock)->rlock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&(&pool->lock)->rlock);
                               lock(&pool->lock/1);
                               lock(&(&pool->lock)->rlock);
  lock(console_owner);

 *** DEADLOCK ***

4 locks held by swapper/0/0:
 #0:  (kernel/workqueue.c:5442){+.-.}, at: [<0000000035540175>] lockdep_copy_map /./include/linux/lockdep.h:174 [inline]
 #0:  (kernel/workqueue.c:5442){+.-.}, at: [<0000000035540175>] call_timer_fn+0xc6/0x6a0 /kernel/time/timer.c:1269
 #1:  (rcu_read_lock_sched){....}, at: [<00000000002fc9b2>] show_workqueue_state+0x0/0x100 /kernel/workqueue.c:4390
 #2:  (&(&pool->lock)->rlock){-.-.}, at: [<000000005cae8eab>] show_workqueue_state /kernel/workqueue.c:4518 [inline]
 #2:  (&(&pool->lock)->rlock){-.-.}, at: [<000000005cae8eab>] show_workqueue_state.cold+0x22f/0xeb3 /kernel/workqueue.c:4491
 #3:  (console_lock){+.+.}, at: [<000000006e96c9a3>] console_trylock_spinning /kernel/printk/printk.c:1644 [inline]
 #3:  (console_lock){+.+.}, at: [<000000006e96c9a3>] vprintk_emit+0x11a/0x330 /kernel/printk/printk.c:1916

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.133+ #17
Call Trace:
 <IRQ>
 __dump_stack /lib/dump_stack.c:17 [inline]
 dump_stack+0xca/0x134 /lib/dump_stack.c:53
 print_circular_bug.isra.0.cold+0x2dc/0x425 /kernel/locking/lockdep.c:1258
 </IRQ>
workqueue events_power_efficient: flags=0x80
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256
    pending: neigh_periodic_work, check_lifetime
workqueue mm_percpu_wq: flags=0x8
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
    pending: vmstat_update
workqueue dm_bufio_cache: flags=0x8
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
    pending: work_fn
workqueue ipv6_addrconf: flags=0x40008
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1
    pending: addrconf_verify_work