===============================
[ INFO: suspicious RCU usage. ]
4.9.109-g7143cbf #3 Not tainted
-------------------------------
kernel/rcu/tree_plugin.h:678 Illegal synchronize_rcu() in RCU read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
4 locks held by modprobe/25419:
 #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff810db77b>] __do_page_fault+0x36b/0xd50 arch/x86/mm/fault.c:1336
 #1:  (rcu_read_lock){......}, at: [<ffffffff8143752a>] filemap_map_pages+0xfa/0xd40 mm/filemap.c:2229
 #2:  (&(ptlock_ptr(page))->rlock#2){+.+...}, at: [<ffffffff814cbc28>] spin_lock include/linux/spinlock.h:302 [inline]
 #2:  (&(ptlock_ptr(page))->rlock#2){+.+...}, at: [<ffffffff814cbc28>] pte_alloc_one_map mm/memory.c:2906 [inline]
 #2:  (&(ptlock_ptr(page))->rlock#2){+.+...}, at: [<ffffffff814cbc28>] alloc_set_pte+0xb98/0x11d0 mm/memory.c:3004
 #3:  (rcu_callback){......}, at: [<ffffffff8128777e>] __rcu_reclaim kernel/rcu/rcu.h:108 [inline]
 #3:  (rcu_callback){......}, at: [<ffffffff8128777e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 #3:  (rcu_callback){......}, at: [<ffffffff8128777e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 #3:  (rcu_callback){......}, at: [<ffffffff8128777e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 #3:  (rcu_callback){......}, at: [<ffffffff8128777e>] rcu_process_callbacks+0x98e/0x12b0 kernel/rcu/tree.c:3037

stack backtrace:
CPU: 1 PID: 25419 Comm: modprobe Not tainted 4.9.109-g7143cbf #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db307d60 ffffffff81eb3e29 ffff8801674cb000 0000000000000000
 0000000000000002 ffffffff83c6df00 ffff8801be331cd8 ffff8801db307d90
 ffffffff81425fc0 ffff8801be331b80 ffff8801d45fee48 ffff8801d45fe648
Call Trace:
 <IRQ> [ 1456.670551]  [<ffffffff81eb3e29>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [ 1456.670551]  [<ffffffff81eb3e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81425fc0>] lockdep_rcu_suspicious.cold.48+0x110/0x141 kernel/locking/lockdep.c:4455
 [<ffffffff81284018>] synchronize_rcu+0x68/0x90 kernel/rcu/tree_plugin.h:675
 [<ffffffff836bcb2a>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836bceb7>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836bd772>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff83021095>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff8128769e>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff8128769e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff8128769e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff8128769e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff8128769e>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a004fb>] __do_softirq+0x20b/0x937 kernel/softirq.c:284
 [<ffffffff8114b227>] invoke_softirq kernel/softirq.c:364 [inline]
 [<ffffffff8114b227>] irq_exit+0x147/0x190 kernel/softirq.c:405
 [<ffffffff839ff0e1>] exiting_irq arch/x86/include/asm/apic.h:659 [inline]
 [<ffffffff839ff0e1>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:960
 [<ffffffff839fb270>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [ 1456.784177]  [<ffffffff81230a4f>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [ 1456.784177]  [<ffffffff81230a4f>] ? lock_is_held+0xff/0x140 kernel/locking/lockdep.c:3796
 [<ffffffff8127c114>] rcu_read_lock_held+0xa4/0xc0 kernel/rcu/update.c:297
 [<ffffffff81437b6c>] radix_tree_deref_slot include/linux/radix-tree.h:199 [inline]
 [<ffffffff81437b6c>] filemap_map_pages+0x73c/0xd40 mm/filemap.c:2240
 [<ffffffff814d1253>] do_fault_around mm/memory.c:3129 [inline]
 [<ffffffff814d1253>] do_read_fault mm/memory.c:3169 [inline]
 [<ffffffff814d1253>] do_fault mm/memory.c:3309 [inline]
 [<ffffffff814d1253>] handle_pte_fault mm/memory.c:3510 [inline]
 [<ffffffff814d1253>] __handle_mm_fault mm/memory.c:3597 [inline]
 [<ffffffff814d1253>] handle_mm_fault+0x1cb3/0x28e0 mm/memory.c:3634
 [<ffffffff810db9bf>] __do_page_fault+0x5af/0xd50 arch/x86/mm/fault.c:1407
 [<ffffffff810dc187>] do_page_fault+0x27/0x30 arch/x86/mm/fault.c:1470
 [<ffffffff839faa88>] page_fault+0x28/0x30 arch/x86/entry/entry_64.S:951
BUG: sleeping function called from invalid context at kernel/locking/mutex.c:620
in_atomic(): 1, irqs_disabled(): 0, pid: 25419, name: modprobe
INFO: lockdep is turned off.
Preemption disabled at:[ 1456.892369] [<ffffffff814cbc28>] spin_lock include/linux/spinlock.h:302 [inline]
Preemption disabled at:[ 1456.892369] [<ffffffff814cbc28>] pte_alloc_one_map mm/memory.c:2906 [inline]
Preemption disabled at:[ 1456.892369] [<ffffffff814cbc28>] alloc_set_pte+0xb98/0x11d0 mm/memory.c:3004
CPU: 1 PID: 25419 Comm: modprobe Not tainted 4.9.109-g7143cbf #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db3078b0 ffffffff81eb3e29 ffffffff814cbc28 0000000000000000
 0000000000000102 ffff8801674cb000 ffff8801674cb000 ffff8801db3078e8
 ffffffff814242c0 ffff8801674cb000 ffffffff83c5b400 000000000000026c
Call Trace:
 <IRQ> [ 1456.943646]  [<ffffffff81eb3e29>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [ 1456.943646]  [<ffffffff81eb3e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff814242c0>] ___might_sleep.cold.123+0x1bc/0x1f5 kernel/sched/core.c:7992
 [<ffffffff811bb625>] __might_sleep+0x95/0x1a0 kernel/sched/core.c:7949
 [<ffffffff839eeba7>] mutex_lock_nested+0x87/0x870 kernel/locking/mutex.c:620
 [<ffffffff81282a87>] exp_funnel_lock kernel/rcu/tree_exp.h:289 [inline]
 [<ffffffff81282a87>] _synchronize_rcu_expedited+0x3a7/0x840 kernel/rcu/tree_exp.h:569
 [<ffffffff81283f73>] synchronize_rcu_expedited kernel/rcu/tree_exp.h:687 [inline]
 [<ffffffff81283f73>] synchronize_rcu.part.62+0xd3/0x110 kernel/rcu/tree_plugin.h:682
 [<ffffffff81283fd7>] synchronize_rcu+0x27/0x90 kernel/rcu/tree_plugin.h:685
 [<ffffffff836bcb2a>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836bceb7>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836bd772>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff83021095>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff8128769e>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff8128769e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff8128769e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff8128769e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff8128769e>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a004fb>] __do_softirq+0x20b/0x937 kernel/softirq.c:284
 [<ffffffff8114b227>] invoke_softirq kernel/softirq.c:364 [inline]
 [<ffffffff8114b227>] irq_exit+0x147/0x190 kernel/softirq.c:405
 [<ffffffff839ff0e1>] exiting_irq arch/x86/include/asm/apic.h:659 [inline]
 [<ffffffff839ff0e1>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:960
 [<ffffffff839fb270>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [ 1457.208343]  [<ffffffff81230a4f>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [ 1457.208343]  [<ffffffff81230a4f>] ? lock_is_held+0xff/0x140 kernel/locking/lockdep.c:3796
 [<ffffffff8127c114>] rcu_read_lock_held+0xa4/0xc0 kernel/rcu/update.c:297
 [<ffffffff81437b6c>] radix_tree_deref_slot include/linux/radix-tree.h:199 [inline]
 [<ffffffff81437b6c>] filemap_map_pages+0x73c/0xd40 mm/filemap.c:2240
 [<ffffffff814d1253>] do_fault_around mm/memory.c:3129 [inline]
 [<ffffffff814d1253>] do_read_fault mm/memory.c:3169 [inline]
 [<ffffffff814d1253>] do_fault mm/memory.c:3309 [inline]
 [<ffffffff814d1253>] handle_pte_fault mm/memory.c:3510 [inline]
 [<ffffffff814d1253>] __handle_mm_fault mm/memory.c:3597 [inline]
 [<ffffffff814d1253>] handle_mm_fault+0x1cb3/0x28e0 mm/memory.c:3634
 [<ffffffff810db9bf>] __do_page_fault+0x5af/0xd50 arch/x86/mm/fault.c:1407
 [<ffffffff810dc187>] do_page_fault+0x27/0x30 arch/x86/mm/fault.c:1470
 [<ffffffff839faa88>] page_fault+0x28/0x30 arch/x86/entry/entry_64.S:951
BUG: scheduling while atomic: modprobe/25419/0x00000102
INFO: lockdep is turned off.
Modules linked in:
Preemption disabled at:[ 1457.310131] [<ffffffff814cbc28>] spin_lock include/linux/spinlock.h:302 [inline]
Preemption disabled at:[ 1457.310131] [<ffffffff814cbc28>] pte_alloc_one_map mm/memory.c:2906 [inline]
Preemption disabled at:[ 1457.310131] [<ffffffff814cbc28>] alloc_set_pte+0xb98/0x11d0 mm/memory.c:3004