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WARNING: CPU: 1 PID: 6081 at kernel/locking/mutex.c:873 __mutex_trylock_slowpath kernel/locking/mutex.c:873 [inline]
WARNING: CPU: 1 PID: 6081 at kernel/locking/mutex.c:873 mutex_trylock+0x2f9/0x3e0 kernel/locking/mutex.c:908
DEBUG_LOCKS_WARN_ON(in_interrupt())[   88.026117] Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 6081 Comm: syz-executor4 Not tainted 4.9.123-g8dd3fc2 #79
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db3077f8 ffffffff81eb9689 ffffffff83c48ac0 00000000ffffffff
 0000000000000000 0000000000000001 0000000000000369 ffff8801db3078b8
 ffffffff81423f75 0000000041b58ab3 ffffffff843bb878 ffffffff81423db6
Call Trace:
 <IRQ> [   88.079033]  [<ffffffff81eb9689>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [   88.079033]  [<ffffffff81eb9689>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81423f75>] panic+0x1bf/0x3bc kernel/panic.c:179
 [<ffffffff81424261>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff81138252>] warn_slowpath_fmt+0xc2/0x100 kernel/panic.c:565
 [<ffffffff839f6db9>] __mutex_trylock_slowpath kernel/locking/mutex.c:873 [inline]
 [<ffffffff839f6db9>] mutex_trylock+0x2f9/0x3e0 kernel/locking/mutex.c:908
 [<ffffffff81284e29>] exp_funnel_lock kernel/rcu/tree_exp.h:256 [inline]
 [<ffffffff81284e29>] _synchronize_rcu_expedited+0x339/0x840 kernel/rcu/tree_exp.h:569
 [<ffffffff81286383>] synchronize_rcu_expedited kernel/rcu/tree_exp.h:687 [inline]
 [<ffffffff81286383>] synchronize_rcu.part.62+0xd3/0x110 kernel/rcu/tree_plugin.h:682
 [<ffffffff812863e7>] synchronize_rcu+0x27/0x90 kernel/rcu/tree_plugin.h:685
 [<ffffffff836c4e2a>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836c51b7>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836c5a72>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff830280f5>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff81289aae>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff81289aae>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff81289aae>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff81289aae>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff81289aae>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a08880>] __do_softirq+0x210/0x940 kernel/softirq.c:288
 [<ffffffff8114d554>] invoke_softirq kernel/softirq.c:368 [inline]
 [<ffffffff8114d554>] irq_exit+0x114/0x150 kernel/softirq.c:409
 [<ffffffff83a07461>] exiting_irq arch/x86/include/asm/apic.h:669 [inline]
 [<ffffffff83a07461>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:962
 [<ffffffff83a035f0>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [   88.341647]  [<ffffffff8123cf93>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [   88.341647]  [<ffffffff8123cf93>] ? lock_acquire+0x173/0x3e0 kernel/locking/lockdep.c:3759
 [<ffffffff814c2f5a>] __might_fault+0x14a/0x1d0 mm/memory.c:4029
 [<ffffffff812af5f8>] copy_to_user arch/x86/include/asm/uaccess.h:727 [inline]
 [<ffffffff812af5f8>] SYSC_clock_gettime kernel/time/posix-timers.c:1043 [inline]
 [<ffffffff812af5f8>] SyS_clock_gettime+0x178/0x1f0 kernel/time/posix-timers.c:1031
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a01c93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..