rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1):
 P6648/2:b..l

rcu: 	(detected by 1, t=10502 jiffies, g=27073, q=10390 ncpus=2)
task:kworker/0:6     state:R
  running task     stack:22376 pid:6648  tgid:6648  ppid:2      task_flags:0x4208060 flags:0x00004000
Workqueue: mld mld_ifc_work

Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:7145
 preempt_schedule+0xae/0xc0 kernel/sched/core.c:7169
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __local_bh_enable_ip+0x13e/0x1c0 kernel/softirq.c:414
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:910 [inline]
 __dev_queue_xmit+0x1d79/0x3b50 net/core/dev.c:4752
 dev_queue_xmit include/linux/netdevice.h:3361 [inline]
 neigh_hh_output include/net/neighbour.h:531 [inline]
 neigh_output include/net/neighbour.h:545 [inline]
 ip6_finish_output2+0x11bc/0x16a0 net/ipv6/ip6_output.c:141
 NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318
 mld_sendpack+0x800/0xd80 net/ipv6/mcast.c:1860
 mld_send_cr net/ipv6/mcast.c:2159 [inline]
 mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2698
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x439/0x7d0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>