======================================
| [   23.949368][    C2] 1 lock held by ksoftirqd/2/29:
| [ 23.949544][ C2] #0: ffffc9000020fbc0 ((&n->timer)){+.-.}-{0:0}, at: call_timer_fn (./include/linux/lockdep.h:31 kernel/time/timer.c:1779) 
| [   23.949862][    C2]
| [   23.949862][    C2] stack backtrace:
[   23.950079][    C2] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   23.950081][    C2] Call Trace:
[   23.950083][    C2]  <TASK>
[ 23.950086][ C2] dump_stack_lvl (lib/dump_stack.c:123) 
[ 23.950094][ C2] lockdep_rcu_suspicious (kernel/locking/lockdep.c:6848) 
[ 23.950103][ C2] icmp6_send (./include/net/net_namespace.h:404 ./include/linux/netdevice.h:2669 net/ipv6/icmp.c:476) 
[ 23.950111][ C2] ? __pfx_unwind_next_frame (arch/x86/kernel/unwind_orc.c:469) 
[ 23.950126][ C2] ? __pfx_icmp6_send (net/ipv6/icmp.c:452) 
[ 23.950134][ C2] ? __pfx_validate_chain (kernel/locking/lockdep.c:3862) 
[ 23.950139][ C2] ? hlock_class (./arch/x86/include/asm/bitops.h:227 ./arch/x86/include/asm/bitops.h:239 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 kernel/locking/lockdep.c:230) 
[ 23.950142][ C2] ? mark_lock (kernel/locking/lockdep.c:4729 (discriminator 3)) 
[ 23.950151][ C2] ? __lock_acquire (kernel/locking/lockdep.c:5228) 
[ 23.950157][ C2] ? find_held_lock (kernel/locking/lockdep.c:5341) 
[ 23.950164][ C2] ? __lock_release (kernel/locking/lockdep.c:5527) 
[ 23.950166][ C2] ? neigh_invalidate (net/core/neighbour.c:1008) 
[ 23.950172][ C2] ? __pfx___lock_release (kernel/locking/lockdep.c:5503) 
[ 23.950175][ C2] ? lock_acquire.part.0 (kernel/locking/lockdep.c:469 kernel/locking/lockdep.c:5853) 
[ 23.950186][ C2] ip6_link_failure (./include/linux/skbuff.h:1152 net/ipv6/route.c:2801) 
[ 23.950194][ C2] ndisc_error_report (./include/net/dst.h:429 net/ipv6/ndisc.c:731) 
[ 23.950200][ C2] neigh_invalidate (net/core/neighbour.c:1008) 
[ 23.950209][ C2] neigh_timer_handler (net/core/neighbour.c:1109 (discriminator 2)) 
[ 23.950218][ C2] ? __pfx_neigh_timer_handler (net/core/neighbour.c:1032) 
[ 23.950222][ C2] call_timer_fn (kernel/time/timer.c:1789) 
[ 23.950225][ C2] ? call_timer_fn (./include/linux/lockdep.h:31 kernel/time/timer.c:1779) 
[ 23.950227][ C2] ? call_timer_fn (./include/linux/lockdep.h:31 kernel/time/timer.c:1779) 
[ 23.950231][ C2] ? __pfx_call_timer_fn (kernel/time/timer.c:1766) 
[ 23.950234][ C2] ? mark_lock (kernel/locking/lockdep.c:4729 (discriminator 3)) 
[ 23.950251][ C2] __run_timers (kernel/time/timer.c:1841 kernel/time/timer.c:2414) 
[ 23.950255][ C2] ? __pfx_neigh_timer_handler (net/core/neighbour.c:1032) 
[ 23.950265][ C2] ? __pfx___run_timers (kernel/time/timer.c:2385) 
[ 23.950273][ C2] ? do_raw_spin_lock (./arch/x86/include/asm/atomic.h:107 ./include/linux/atomic/atomic-arch-fallback.h:2170 ./include/linux/atomic/atomic-instrumented.h:1302 ./include/asm-generic/qspinlock.h:111 kernel/locking/spinlock_debug.c:116) 
[ 23.950278][ C2] ? __pfx_do_raw_spin_lock (kernel/locking/spinlock_debug.c:114) 
[ 23.950283][ C2] ? lock_acquire (kernel/locking/lockdep.c:5824) 
[ 23.950285][ C2] ? run_timer_softirq (kernel/time/timer.c:2426 kernel/time/timer.c:2418 kernel/time/timer.c:2435 kernel/time/timer.c:2445) 
[ 23.950295][ C2] run_timer_softirq (kernel/time/timer.c:2427 kernel/time/timer.c:2418 kernel/time/timer.c:2435 kernel/time/timer.c:2445) 
[ 23.950300][ C2] handle_softirqs (kernel/softirq.c:561) 
[ 23.950308][ C2] ? __pfx_run_ksoftirqd (kernel/softirq.c:943) 
[ 23.950313][ C2] run_ksoftirqd (kernel/softirq.c:418 kernel/softirq.c:951 kernel/softirq.c:942) 
[ 23.950316][ C2] smpboot_thread_fn (kernel/smpboot.c:164 (discriminator 3)) 
[ 23.950322][ C2] ? __pfx_smpboot_thread_fn (kernel/smpboot.c:107) 
[ 23.950328][ C2] kthread (kernel/kthread.c:464) 
[ 23.950335][ C2] ? __pfx_kthread (kernel/kthread.c:413) 
[ 23.950344][ C2] ? __pfx_kthread (kernel/kthread.c:413) 
[ 23.950350][ C2] ret_from_fork (arch/x86/kernel/process.c:148) 
[ 23.950354][ C2] ? __pfx_kthread (kernel/kthread.c:413) 


Finger prints:
lockdep_rcu_suspicious:icmp6_send:ip6_link_failure:ndisc_error_report:neigh_invalidate