======================================
| [  927.984132][T21381] 1 lock held by ip/21381:
| [  927.984336][T21381]  #0: ffffffff8d27e6e8 (rtnl_mutex){+.+.}-{4:4}, at: rtm_new_nexthop (net/ipv4/nexthop.c:3216 net/ipv4/nexthop.c:3271)
| [  927.984635][T21381]
| [  927.984635][T21381] stack backtrace:
[  927.984858][T21381] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  927.984859][T21381] Call Trace:
[  927.984862][T21381]  <TASK>
[  927.984864][T21381]  dump_stack_lvl (lib/dump_stack.c:122)
[  927.984871][T21381]  lockdep_rcu_suspicious.cold (kernel/locking/lockdep.c:6877)
[  927.984877][T21381]  fib6_update_sernum (net/ipv6/ip6_fib.c:111 (discriminator 10))
[  927.984881][T21381]  nh_rt_cache_flush (net/ipv4/nexthop.c:2204 (discriminator 4))
[  927.984885][T21381]  replace_nexthop (net/ipv4/nexthop.c:2570)
[  927.984891][T21381]  insert_nexthop (net/ipv4/nexthop.c:2605)
[  927.984898][T21381]  rtm_new_nexthop (net/ipv4/nexthop.c:2971 net/ipv4/nexthop.c:3275)
[  927.984903][T21381]  ? insert_nexthop (net/ipv4/nexthop.c:3246)
[  927.984905][T21381]  ? lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  927.984909][T21381]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  927.984918][T21381]  ? lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  927.984920][T21381]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  927.984927][T21381]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  927.984929][T21381]  ? insert_nexthop (net/ipv4/nexthop.c:3246)
[  927.984931][T21381]  ? __lock_release.isra.0 (kernel/locking/lockdep.c:5536)
[  927.984935][T21381]  ? insert_nexthop (net/ipv4/nexthop.c:3246)
[  927.984937][T21381]  rtnetlink_rcv_msg (net/core/rtnetlink.c:6958)
[  927.984942][T21381]  ? rtnl_fdb_dump (net/core/rtnetlink.c:6861)
[  927.984944][T21381]  ? __lock_acquire (kernel/locking/lockdep.c:5237 (discriminator 1))
[  927.984948][T21381]  ? lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  927.984949][T21381]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  927.984952][T21381]  netlink_rcv_skb (net/netlink/af_netlink.c:2550)
[  927.984956][T21381]  ? rtnl_fdb_dump (net/core/rtnetlink.c:6861)
[  927.984959][T21381]  ? netlink_ack (net/netlink/af_netlink.c:2527)
[  927.984965][T21381]  ? 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))
[  927.984967][T21381]  ? 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))
[  927.984972][T21381]  netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344)
[  927.984976][T21381]  ? netlink_attachskb (net/netlink/af_netlink.c:1329)
[  927.984978][T21381]  ? __alloc_skb (./include/linux/bottom_half.h:20 (discriminator 1) net/core/skbuff.c:695 (discriminator 1))
[  927.984981][T21381]  ? napi_skb_cache_get (net/core/skbuff.c:674)
[  927.984984][T21381]  ? __lock_acquire (kernel/locking/lockdep.c:5237 (discriminator 1))
[  927.984987][T21381]  netlink_sendmsg (net/netlink/af_netlink.c:1894)
[  927.984991][T21381]  ? netlink_unicast (net/netlink/af_netlink.c:1813)
[  927.984995][T21381]  ? __might_fault (mm/memory.c:7217 (discriminator 4))
[  927.985001][T21381]  ____sys_sendmsg (net/socket.c:727 (discriminator 4) net/socket.c:742 (discriminator 4) net/socket.c:2592 (discriminator 4))
[  927.985004][T21381]  ? copy_msghdr_from_user (net/socket.c:2532)
[  927.985006][T21381]  ? get_timestamp.constprop.0 (net/socket.c:2538)
[  927.985007][T21381]  ? move_addr_to_kernel (net/socket.c:2518)
[  927.985011][T21381]  ? lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  927.985013][T21381]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  927.985016][T21381]  ___sys_sendmsg (net/socket.c:2648)
[  927.985018][T21381]  ? copy_msghdr_from_user (net/socket.c:2635)
[  927.985020][T21381]  ? __lock_release.isra.0 (kernel/locking/lockdep.c:5536)
[  927.985031][T21381]  ? 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))
[  927.985036][T21381]  __sys_sendmsg (net/socket.c:2678 (discriminator 1))
[  927.985044][T21381]  ? __sys_sendmsg_sock (net/socket.c:2663)
[  927.985050][T21381]  ? 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))
[  927.985054][T21381]  ? rcu_is_watching (./include/linux/context_tracking.h:128 (discriminator 1) kernel/rcu/tree.c:752 (discriminator 1))
[  927.985058][T21381]  ? rcu_is_watching (./include/linux/context_tracking.h:128 (discriminator 1) kernel/rcu/tree.c:752 (discriminator 1))
[  927.985061][T21381]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
[  927.985066][T21381]  ? exc_page_fault (arch/x86/mm/fault.c:1480 (discriminator 3) arch/x86/mm/fault.c:1527 (discriminator 3))
[  927.985069][T21381]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
[  927.985072][T21381] RIP: 0033:0x7faebc3e7c5e
[  927.985076][T21381] 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
[  927.985078][T21381] RSP: 002b:00007ffc66ea9970 EFLAGS: 00000202 ORIG_RAX: 000000000000002e
[  927.985081][T21381] RAX: ffffffffffffffda RBX: 000000000048a910 RCX: 00007faebc3e7c5e
[  927.985083][T21381] RDX: 0000000000000000 RSI: 00007ffc66ea9a30 RDI: 0000000000000005
[  927.985084][T21381] RBP: 00007ffc66ea9980 R08: 0000000000000000 R09: 0000000000000000
[  927.985084][T21381] R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000001


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