===============================
[ INFO: suspicious RCU usage. ]
4.9.155+ #27 Not tainted
-------------------------------
net/ipv6/ip6_fib.c:1470 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
4 locks held by swapper/0/0:
 #0:  (((&net->ipv6.ip6_fib_timer))){+.-...}, at: [<ffffffff812624fe>] lockdep_copy_map include/linux/lockdep.h:165 [inline]
 #0:  (((&net->ipv6.ip6_fib_timer))){+.-...}, at: [<ffffffff812624fe>] call_timer_fn+0xde/0x6d0 kernel/time/timer.c:1309
 #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-...}, at: [<ffffffff826ef1e2>] spin_lock_bh include/linux/spinlock.h:307 [inline]
 #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-...}, at: [<ffffffff826ef1e2>] fib6_run_gc+0xa2/0x2e0 net/ipv6/ip6_fib.c:1816
 #2:  (rcu_read_lock){......}, at: [<ffffffff826e69f0>] __fib6_clean_all+0x0/0x230 net/ipv6/ip6_fib.c:1703
 #3:  (&tb->tb6_lock){++--..}, at: [<ffffffff826e6ad3>] __fib6_clean_all+0xe3/0x230 net/ipv6/ip6_fib.c:1717

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.155+ #27
 ffff8801db607890 ffffffff81b47871 ffff8801c5839180 0000000000000000
 0000000000000002 00000000000005be ffffffff8302d180 ffff8801db6078c0
 ffffffff813fed99 ffff8801db607ae0 dffffc0000000000 00000000ffffffff
Call Trace:
 <IRQ> [  670.642118]  [<ffffffff81b47871>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [  670.642118]  [<ffffffff81b47871>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff813fed99>] lockdep_rcu_suspicious.cold+0x10a/0x149 kernel/locking/lockdep.c:4455
 [<ffffffff826ee93f>] fib6_del+0x81f/0xb20 net/ipv6/ip6_fib.c:1470
 [<ffffffff826eeedc>] fib6_clean_node+0x29c/0x4d0 net/ipv6/ip6_fib.c:1657
 [<ffffffff826e62c0>] fib6_walk_continue+0x3e0/0x630 net/ipv6/ip6_fib.c:1583
 [<ffffffff826e687d>] fib6_walk+0x9d/0xf0 net/ipv6/ip6_fib.c:1628
 [<ffffffff826e69b7>] fib6_clean_tree+0xe7/0x120 net/ipv6/ip6_fib.c:1702
 [<ffffffff826e6aeb>] __fib6_clean_all+0xfb/0x230 net/ipv6/ip6_fib.c:1718
 [<ffffffff826ef264>] fib6_clean_all net/ipv6/ip6_fib.c:1729 [inline]
 [<ffffffff826ef264>] fib6_run_gc+0x124/0x2e0 net/ipv6/ip6_fib.c:1826
 [<ffffffff826ef43d>] fib6_gc_timer_cb+0x1d/0x30 net/ipv6/ip6_fib.c:1841
 [<ffffffff81262587>] call_timer_fn+0x167/0x6d0 kernel/time/timer.c:1319
 [<ffffffff81262d4b>] expire_timers+0x25b/0x5c0 kernel/time/timer.c:1359
 [<ffffffff812632af>] __run_timers kernel/time/timer.c:1674 [inline]
 [<ffffffff812632af>] run_timer_softirq+0x1ff/0x620 kernel/time/timer.c:1687
 [<ffffffff8281be7d>] __do_softirq+0x22d/0x964 kernel/softirq.c:288
 [<ffffffff810eecd9>] invoke_softirq kernel/softirq.c:368 [inline]
 [<ffffffff810eecd9>] irq_exit+0x119/0x160 kernel/softirq.c:409
 [<ffffffff8281a9be>] exiting_irq arch/x86/include/asm/apic.h:669 [inline]
 [<ffffffff8281a9be>] smp_apic_timer_interrupt+0x7e/0xb0 arch/x86/kernel/apic/apic.c:962
 [<ffffffff8281822d>] apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [  670.920061]  [<ffffffff82815692>] ? native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:56
 [<ffffffff81068160>] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:428
 [<ffffffff82815ae6>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff811f1233>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff811f1233>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff811f1233>] cpu_startup_entry+0x283/0x3a0 kernel/sched/idle.c:303
 [<ffffffff82804124>] rest_init+0x18b/0x194 init/main.c:409
 [<ffffffff83420948>] start_kernel+0x619/0x64d init/main.c:664
 [<ffffffff8341f29a>] x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:196
 [<ffffffff8341f3d3>] x86_64_start_kernel+0x137/0x15a arch/x86/kernel/head64.c:177