======================================
| [ 50.002009][ C2] common_startup_64 (arch/x86/kernel/head_64.S:421) 
| [   50.002154][    C2]
| [   50.002223][    C2]
| [   50.002223][    C2] stack backtrace:
[   50.002700][    C2] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[   50.003097][    C2] Call Trace:
[   50.003211][    C2]  <IRQ>
[ 50.003287][ C2] dump_stack_lvl (lib/dump_stack.c:117) 
[ 50.003435][ C2] print_irq_inversion_bug.part.0 (kernel/locking/lockdep.c:4024) 
[ 50.003622][ C2] ? common_startup_64 (arch/x86/kernel/head_64.S:421) 
[ 50.003850][ C2] ? __pfx_print_irq_inversion_bug.part.0 (kernel/locking/lockdep.c:4024) 
[ 50.004018][ C2] ? __pfx_usage_skip (kernel/locking/lockdep.c:2264) 
[ 50.004154][ C2] ? __pfx_usage_match (kernel/locking/lockdep.c:2256) 
[ 50.004290][ C2] ? arch_stack_walk (arch/x86/kernel/stacktrace.c:24) 
[ 50.004509][ C2] mark_lock_irq (kernel/locking/lockdep.c:4244) 
[ 50.004647][ C2] ? __pfx_mark_lock_irq (kernel/locking/lockdep.c:4207) 
[ 50.004789][ C2] ? stack_trace_save (kernel/stacktrace.c:123) 
[ 50.004929][ C2] ? add_chain_cache (kernel/locking/lockdep.c:3730) 
[ 50.005148][ C2] ? save_trace (kernel/locking/lockdep.c:586) 
[ 50.005286][ C2] mark_lock (kernel/locking/lockdep.c:4678) 
[ 50.005390][ C2] mark_usage (kernel/locking/lockdep.c:4567) 
[ 50.005502][ C2] __lock_acquire (kernel/locking/lockdep.c:5091) 
[ 50.005641][ C2] ? __lock_acquire (kernel/locking/lockdep.c:5137) 
[ 50.005858][ C2] ? __pfx_br_forward_delay_timer_expired (net/bridge/br_stp_timer.c:80) bridge
[ 50.006108][ C2] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756) 
[ 50.006249][ C2] ? br_forward_delay_timer_expired (net/bridge/br_stp_timer.c:87) bridge
[ 50.006560][ C2] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 50.006699][ C2] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 50.006839][ C2] ? br_forward_delay_timer_expired (net/bridge/br_stp_timer.c:87) bridge
[ 50.007050][ C2] ? lock_acquire (kernel/locking/lockdep.c:5727) 
[ 50.007189][ C2] ? br_forward_delay_timer_expired (net/bridge/br_stp_timer.c:87) bridge
[ 50.007408][ C2] _raw_spin_lock (./include/linux/spinlock_api_smp.h:134 kernel/locking/spinlock.c:154) 
[ 50.007546][ C2] ? br_forward_delay_timer_expired (net/bridge/br_stp_timer.c:87) bridge
[ 50.007755][ C2] br_forward_delay_timer_expired (net/bridge/br_stp_timer.c:87) bridge
[ 50.008052][ C2] ? __pfx_br_forward_delay_timer_expired (net/bridge/br_stp_timer.c:80) bridge
[ 50.008297][ C2] call_timer_fn (kernel/time/timer.c:1793) 
[ 50.008436][ C2] ? call_timer_fn (./include/linux/lockdep.h:31 kernel/time/timer.c:1783) 
[ 50.008654][ C2] ? call_timer_fn (./include/linux/lockdep.h:31 kernel/time/timer.c:1783) 
[ 50.008795][ C2] ? __pfx_call_timer_fn (kernel/time/timer.c:1770) 
[ 50.008934][ C2] ? mark_lock (kernel/locking/lockdep.c:4656 (discriminator 3)) 
[ 50.009043][ C2] __run_timers (kernel/time/timer.c:1845 kernel/time/timer.c:2418) 
[ 50.009180][ C2] ? __pfx_br_forward_delay_timer_expired (net/bridge/br_stp_timer.c:80) bridge
[ 50.009505][ C2] ? __pfx___run_timers (kernel/time/timer.c:2389) 
[ 50.009643][ C2] ? __lock_release (kernel/locking/lockdep.c:5430) 
[ 50.009782][ C2] ? do_raw_spin_lock (./arch/x86/include/asm/atomic.h:115 ./include/linux/atomic/atomic-arch-fallback.h:2170 ./include/linux/atomic/atomic-instrumented.h:1302 ./include/asm-generic/qspinlock.h:111 kernel/locking/spinlock_debug.c:116) 
[ 50.009938][ C2] ? __pfx_do_raw_spin_lock (kernel/locking/spinlock_debug.c:114) 
[ 50.010250][ C2] ? lock_acquire (kernel/locking/lockdep.c:5727) 
[ 50.010389][ C2] ? timer_expire_remote (kernel/time/timer.c:2429 kernel/time/timer.c:2422 kernel/time/timer.c:2181) 
[ 50.010529][ C2] timer_expire_remote (kernel/time/timer.c:2430 kernel/time/timer.c:2422 kernel/time/timer.c:2181) 
[ 50.010668][ C2] tmigr_handle_remote_cpu (./arch/x86/include/asm/irqflags.h:26 ./arch/x86/include/asm/irqflags.h:67 ./arch/x86/include/asm/irqflags.h:127 kernel/time/timer_migration.c:925) 
[ 50.010886][ C2] ? __pfx_tmigr_handle_remote_cpu (kernel/time/timer_migration.c:869) 
[ 50.011059][ C2] tmigr_handle_remote_up (kernel/time/timer_migration.c:1003) 
[ 50.011197][ C2] tmigr_handle_remote (kernel/time/timer_migration.c:488 kernel/time/timer_migration.c:1061) 
[ 50.011335][ C2] ? __pfx_tmigr_handle_remote (kernel/time/timer_migration.c:1026) 
[ 50.011560][ C2] __do_softirq (kernel/softirq.c:554) 
[ 50.011706][ C2] irq_exit_rcu (kernel/softirq.c:428 kernel/softirq.c:633 kernel/softirq.c:645) 
[ 50.011812][ C2] sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1043 arch/x86/kernel/apic/apic.c:1043) 
[   50.011954][    C2]  </IRQ>
[   50.012026][    C2]  <TASK>
[ 50.012175][ C2] asm_sysvec_apic_timer_interrupt (./arch/x86/include/asm/idtentry.h:702) 
[ 50.012349][ C2] RIP: 0010:default_idle (./arch/x86/include/asm/irqflags.h:37 ./arch/x86/include/asm/irqflags.h:72 arch/x86/kernel/process.c:743) 
[ 50.012499][ C2] Code: 4c 01 c7 4c 29 c2 e9 72 ff ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 93 20 35 00 fb f4 <fa> c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
All code
========
   0:	4c 01 c7             	add    %r8,%rdi
   3:	4c 29 c2             	sub    %r8,%rdx
   6:	e9 72 ff ff ff       	jmp    0xffffffffffffff7d
   b:	90                   	nop
   c:	90                   	nop
   d:	90                   	nop
   e:	90                   	nop
   f:	90                   	nop
  10:	90                   	nop
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
  16:	90                   	nop
  17:	90                   	nop
  18:	90                   	nop
  19:	90                   	nop
  1a:	90                   	nop
  1b:	f3 0f 1e fa          	endbr64
  1f:	66 90                	xchg   %ax,%ax
  21:	0f 00 2d 93 20 35 00 	verw   0x352093(%rip)        # 0x3520bb
  28:	fb                   	sti
  29:	f4                   	hlt
  2a:*	fa                   	cli		<-- trapping instruction
  2b:	c3                   	ret
  2c:	cc                   	int3
  2d:	cc                   	int3
  2e:	cc                   	int3
  2f:	cc                   	int3
  30:	66 66 2e 0f 1f 84 00 	data16 cs nopw 0x0(%rax,%rax,1)
  37:	00 00 00 00 
  3b:	90                   	nop
  3c:	90                   	nop
  3d:	90                   	nop
  3e:	90                   	nop
  3f:	90                   	nop

Code starting with the faulting instruction
===========================================
   0:	fa                   	cli
   1:	c3                   	ret
   2:	cc                   	int3
   3:	cc                   	int3
   4:	cc                   	int3
   5:	cc                   	int3
   6:	66 66 2e 0f 1f 84 00 	data16 cs nopw 0x0(%rax,%rax,1)
   d:	00 00 00 00 
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
[   50.013091][    C2] RSP: 0018:ffffc9000015fdf8 EFLAGS: 00000242
[   50.013270][    C2] RAX: 000000000012aa61 RBX: 1ffff9200002bfc1 RCX: ffffffff9650f9e5
[   50.013579][    C2] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff93eaa4a4
[   50.013797][    C2] RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed1006c2709c
[   50.014026][    C2] R10: ffff8880361384e3 R11: ffff88803612d9b0 R12: 0000000000000000
[   50.014316][    C2] R13: ffff888001b7c5c0 R14: dffffc0000000000 R15: 0000000000000000
[ 50.014523][ C2] ? ct_kernel_exit.constprop.0 (kernel/context_tracking.c:147) 
[ 50.014662][ C2] ? cpuidle_idle_call (kernel/sched/idle.c:192) 
[ 50.014803][ C2] default_idle_call (./include/linux/cpuidle.h:143 kernel/sched/idle.c:118) 
[ 50.015020][ C2] cpuidle_idle_call (kernel/sched/idle.c:192) 
[ 50.015161][ C2] ? __pfx_cpuidle_idle_call (kernel/sched/idle.c:168) 
[ 50.015298][ C2] ? tsc_verify_tsc_adjust (arch/x86/kernel/tsc_sync.c:59) 
[ 50.015438][ C2] do_idle (kernel/sched/idle.c:332) 
[ 50.015624][ C2] cpu_startup_entry (kernel/sched/idle.c:429 (discriminator 1)) 
[ 50.015761][ C2] start_secondary (arch/x86/kernel/smpboot.c:201 arch/x86/kernel/smpboot.c:281) 
[ 50.015896][ C2] ? __pfx_start_secondary (arch/x86/kernel/smpboot.c:231) 


Finger prints:
common_startup_64:dump_stack_lvl:mark_lock_irq:mark_lock