======================================
| [  838.040337][T12218] 1 lock held by ip/12218:
| [  838.040464][T12218]  #0: ffffffffa087e6e8 (rtnl_mutex){+.+.}-{4:4}, at: rtm_new_nexthop (net/ipv4/nexthop.c:3216 net/ipv4/nexthop.c:3271)
| [  838.040721][T12218]
| [  838.040721][T12218] stack backtrace:
[  838.040898][T12218] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  838.040899][T12218] Call Trace:
[  838.040901][T12218]  <TASK>
[  838.040902][T12218]  dump_stack_lvl (lib/dump_stack.c:122)
[  838.040909][T12218]  lockdep_rcu_suspicious.cold (kernel/locking/lockdep.c:6877)
[  838.040915][T12218]  fib6_update_sernum (net/ipv6/ip6_fib.c:111 (discriminator 10))
[  838.040919][T12218]  nh_rt_cache_flush (net/ipv4/nexthop.c:2204 (discriminator 4))
[  838.040924][T12218]  replace_nexthop (net/ipv4/nexthop.c:2570)
[  838.040929][T12218]  insert_nexthop (net/ipv4/nexthop.c:2605)
[  838.040934][T12218]  rtm_new_nexthop (net/ipv4/nexthop.c:2971 net/ipv4/nexthop.c:3275)
[  838.040937][T12218]  ? insert_nexthop (net/ipv4/nexthop.c:3246)
[  838.040939][T12218]  ? lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  838.040942][T12218]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  838.040949][T12218]  ? lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  838.040950][T12218]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  838.040956][T12218]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  838.040957][T12218]  ? insert_nexthop (net/ipv4/nexthop.c:3246)
[  838.040959][T12218]  ? __lock_release.isra.0 (kernel/locking/lockdep.c:5536)
[  838.040963][T12218]  ? insert_nexthop (net/ipv4/nexthop.c:3246)
[  838.040965][T12218]  rtnetlink_rcv_msg (net/core/rtnetlink.c:6958)
[  838.040970][T12218]  ? rtnl_fdb_dump (net/core/rtnetlink.c:6861)
[  838.040973][T12218]  ? __lock_acquire (kernel/locking/lockdep.c:5237 (discriminator 1))
[  838.040977][T12218]  ? lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  838.040978][T12218]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  838.040981][T12218]  netlink_rcv_skb (net/netlink/af_netlink.c:2550)
[  838.040985][T12218]  ? rtnl_fdb_dump (net/core/rtnetlink.c:6861)
[  838.040988][T12218]  ? netlink_ack (net/netlink/af_netlink.c:2527)
[  838.040994][T12218]  ? netlink_deliver_tap (./include/linux/rcupdate.h:322 (discriminator 1) ./include/linux/rcupdate.h:881 (discriminator 1) ./include/net/netns/generic.h:48 (discriminator 1) net/netlink/af_netlink.c:333 (discriminator 1))
[  838.040996][T12218]  ? netlink_deliver_tap (./include/linux/rcupdate.h:322 (discriminator 1) ./include/linux/rcupdate.h:881 (discriminator 1) net/netlink/af_netlink.c:340 (discriminator 1))
[  838.041001][T12218]  netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344)
[  838.041005][T12218]  ? netlink_attachskb (net/netlink/af_netlink.c:1329)
[  838.041007][T12218]  ? __alloc_skb (./include/linux/bottom_half.h:20 (discriminator 1) net/core/skbuff.c:695 (discriminator 1))
[  838.041010][T12218]  ? napi_skb_cache_get (net/core/skbuff.c:674)
[  838.041013][T12218]  ? __lock_acquire (kernel/locking/lockdep.c:5237 (discriminator 1))
[  838.041016][T12218]  netlink_sendmsg (net/netlink/af_netlink.c:1894)
[  838.041020][T12218]  ? netlink_unicast (net/netlink/af_netlink.c:1813)
[  838.041024][T12218]  ? __might_fault (mm/memory.c:7217 (discriminator 4))
[  838.041030][T12218]  ____sys_sendmsg (net/socket.c:727 (discriminator 4) net/socket.c:742 (discriminator 4) net/socket.c:2592 (discriminator 4))
[  838.041033][T12218]  ? copy_msghdr_from_user (net/socket.c:2532)
[  838.041034][T12218]  ? get_timestamp.constprop.0 (net/socket.c:2538)
[  838.041036][T12218]  ? move_addr_to_kernel (net/socket.c:2518)
[  838.041040][T12218]  ? lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  838.041042][T12218]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  838.041045][T12218]  ___sys_sendmsg (net/socket.c:2648)
[  838.041047][T12218]  ? copy_msghdr_from_user (net/socket.c:2635)
[  838.041048][T12218]  ? __lock_release.isra.0 (kernel/locking/lockdep.c:5536)
[  838.041060][T12218]  ? lock_vma_under_rcu (./include/linux/rcupdate.h:322 (discriminator 1) ./include/linux/rcupdate.h:881 (discriminator 1) mm/mmap_lock.c:329 (discriminator 1))
[  838.041065][T12218]  __sys_sendmsg (net/socket.c:2678 (discriminator 1))
[  838.041068][T12218]  ? __sys_sendmsg_sock (net/socket.c:2663)
[  838.041074][T12218]  ? do_user_addr_fault (./arch/x86/include/asm/atomic.h:93 (discriminator 4) ./include/linux/atomic/atomic-arch-fallback.h:949 (discriminator 4) ./include/linux/atomic/atomic-instrumented.h:401 (discriminator 4) ./include/linux/refcount.h:389 (discriminator 4) ./include/linux/refcount.h:432 (discriminator 4) ./include/linux/mmap_lock.h:196 (discriminator 4) ./include/linux/mmap_lock.h:217 (discriminator 4) ./include/linux/mmap_lock.h:264 (discriminator 4) arch/x86/mm/fault.c:1336 (discriminator 4))
[  838.041078][T12218]  ? rcu_is_watching (./include/linux/context_tracking.h:128 (discriminator 1) kernel/rcu/tree.c:752 (discriminator 1))
[  838.041082][T12218]  ? rcu_is_watching (./include/linux/context_tracking.h:128 (discriminator 1) kernel/rcu/tree.c:752 (discriminator 1))
[  838.041085][T12218]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
[  838.041090][T12218]  ? exc_page_fault (arch/x86/mm/fault.c:1480 (discriminator 3) arch/x86/mm/fault.c:1527 (discriminator 3))
[  838.041093][T12218]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
[  838.041095][T12218] RIP: 0033:0x7f861e910c5e
[  838.041099][T12218] Code: 4d 89 d8 e8 34 bd 00 00 4c 8b 5d f8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 11 c9 c3 0f 1f 80 00 00 00 00 48 8b 45 10 0f 05 <c9> c3 83 e2 39 83 fa 08 75 e7 e8 13 ff ff ff 0f 1f 00 f3 0f 1e fa
All code
========
   0:	4d 89 d8             	mov    %r11,%r8
   3:	e8 34 bd 00 00       	call   0xbd3c
   8:	4c 8b 5d f8          	mov    -0x8(%rbp),%r11
   c:	41 8b 93 08 03 00 00 	mov    0x308(%r11),%edx
  13:	59                   	pop    %rcx
  14:	5e                   	pop    %rsi
  15:	48 83 f8 fc          	cmp    $0xfffffffffffffffc,%rax
  19:	74 11                	je     0x2c
  1b:	c9                   	leave
  1c:	c3                   	ret
  1d:	0f 1f 80 00 00 00 00 	nopl   0x0(%rax)
  24:	48 8b 45 10          	mov    0x10(%rbp),%rax
  28:	0f 05                	syscall
  2a:*	c9                   	leave		<-- trapping instruction
  2b:	c3                   	ret
  2c:	83 e2 39             	and    $0x39,%edx
  2f:	83 fa 08             	cmp    $0x8,%edx
  32:	75 e7                	jne    0x1b
  34:	e8 13 ff ff ff       	call   0xffffffffffffff4c
  39:	0f 1f 00             	nopl   (%rax)
  3c:	f3 0f 1e fa          	endbr64

Code starting with the faulting instruction
===========================================
   0:	c9                   	leave
   1:	c3                   	ret
   2:	83 e2 39             	and    $0x39,%edx
   5:	83 fa 08             	cmp    $0x8,%edx
   8:	75 e7                	jne    0xfffffffffffffff1
   a:	e8 13 ff ff ff       	call   0xffffffffffffff22
   f:	0f 1f 00             	nopl   (%rax)
  12:	f3 0f 1e fa          	endbr64
[  838.041101][T12218] RSP: 002b:00007fff4d986f50 EFLAGS: 00000202 ORIG_RAX: 000000000000002e
[  838.041104][T12218] RAX: ffffffffffffffda RBX: 000000000048a910 RCX: 00007f861e910c5e
[  838.041106][T12218] RDX: 0000000000000000 RSI: 00007fff4d987010 RDI: 0000000000000005
[  838.041107][T12218] RBP: 00007fff4d986f60 R08: 0000000000000000 R09: 0000000000000000
[  838.041108][T12218] R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000001


Finger prints:
fib6_update_sernum:nh_rt_cache_flush:replace_nexthop:insert_nexthop:rtm_new_nexthop