WARNING: CPU: 2 PID: 0 at kernel/kthread.c:87 free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
Kernel panic - not syncing: panic_on_warn set ...

CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.14.0-rc7-next-20171103+ #10
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 panic+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1c4/0x1e0 kernel/panic.c:546
 report_bug+0x211/0x2d0 lib/bug.c:184
 fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:177
 do_trap_no_signal arch/x86/kernel/traps.c:211 [inline]
 do_trap+0x260/0x390 arch/x86/kernel/traps.c:260
 do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:297
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:310
 invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:906
RIP: 0010:free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
RSP: 0018:ffff88006de07768 EFLAGS: 00010206
RAX: ffff88006dab2040 RBX: ffff88006a6f2580 RCX: ffffffff814937d2
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff88006a6f2708
RBP: ffff88006de07770 R08: 0000000000000000 R09: 1ffff1000dbc0ed4
R10: ffff88006dab2040 R11: 0000000000000001 R12: 1ffff1000dbc0ef0
R13: 1ffff1000dbc0ef4 R14: 0000000000000000 R15: ffff88006de077e0
 free_task+0x134/0x1a0 kernel/fork.c:390
 __put_task_struct+0x229/0x3b0 kernel/fork.c:663
 put_task_struct include/linux/sched/task.h:96 [inline]
 delayed_put_task_struct+0xca/0x3d0 kernel/exit.c:180
 __rcu_reclaim kernel/rcu/rcu.h:172 [inline]
 rcu_do_batch kernel/rcu/tree.c:2676 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2935 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2902 [inline]
 rcu_process_callbacks+0xd74/0x17d0 kernel/rcu/tree.c:2919
 __do_softirq+0x29d/0xbb2 kernel/softirq.c:284
 invoke_softirq kernel/softirq.c:364 [inline]
 irq_exit+0x1d3/0x210 kernel/softirq.c:405
 exiting_irq arch/x86/include/asm/apic.h:540 [inline]
 smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
 apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:578
 </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
RSP: 0018:ffff88006dabfda8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff11
RAX: dffffc0000000000 RBX: 1ffff1000db57fb8 RCX: 0000000000000000
RDX: 1ffffffff0bd9674 RSI: 0000000000000001 RDI: ffffffff85ecb3a0
RBP: ffff88006dabfda8 R08: ffffffff81635769 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
R13: ffff88006dabfe60 R14: ffffffff865b6f60 R15: 0000000000000000
 arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
 default_idle+0xbf/0x430 arch/x86/kernel/process.c:342
 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:333
 default_idle_call+0x36/0x90 kernel/sched/idle.c:98
 cpuidle_idle_call kernel/sched/idle.c:156 [inline]
 do_idle+0x24a/0x3b0 kernel/sched/idle.c:246
 cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:351
 start_secondary+0x2dd/0x3e0 arch/x86/kernel/smpboot.c:279
 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:240
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..