======================================
| xx__-> echo $?
| 0
| xx__-> [   34.788284][    C0] BUG: spinlock bad magic on CPU#0, tc/305
| [ 34.788515][ C0] lock: noop_qdisc+0x240/0x300, .magic: 00000000, .owner: tc/305, .owner_cpu: 0 
[   34.788963][    C0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[   34.789259][    C0] Call Trace:
[   34.789366][    C0]  <IRQ>
[ 34.789435][ C0] dump_stack_lvl (lib/dump_stack.c:122) 
[ 34.789575][ C0] do_raw_spin_unlock (kernel/locking/spinlock_debug.c:100 kernel/locking/spinlock_debug.c:141) 
[ 34.789712][ C0] _raw_spin_unlock (./arch/x86/include/asm/preempt.h:94 ./include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:186) 
[ 34.789853][ C0] net_tx_action (./include/net/sch_generic.h:226 ./include/net/sch_generic.h:217 ./include/net/pkt_sched.h:128 ./include/net/pkt_sched.h:124 net/core/dev.c:5323) 
[ 34.789988][ C0] handle_softirqs (kernel/softirq.c:554) 
[ 34.790125][ C0] ? dev_deactivate_many (./include/linux/bottom_half.h:33 ./include/linux/netdevice.h:4448 net/sched/sch_generic.c:571 net/sched/sch_generic.c:1363) 
[ 34.790261][ C0] do_softirq (kernel/softirq.c:455 kernel/softirq.c:442) 
[   34.790361][    C0]  </IRQ>
[   34.790430][    C0]  <TASK>
[ 34.790496][ C0] __local_bh_enable_ip (kernel/softirq.c:382) 
[ 34.790626][ C0] dev_deactivate_many (net/sched/sch_generic.c:1356) 
[ 34.790760][ C0] ? __pfx___lock_release (kernel/locking/lockdep.c:5411) 
[ 34.790902][ C0] dev_deactivate (./include/linux/list.h:111 ./include/linux/list.h:215 ./include/linux/list.h:229 net/sched/sch_generic.c:1398) 
[ 34.791038][ C0] ? __pfx_dev_deactivate (net/sched/sch_generic.c:1393) 
[ 34.791171][ C0] qdisc_graft (net/sched/sch_api.c:1137) 
[ 34.791306][ C0] ? qdisc_create (net/sched/sch_api.c:1257) 
[ 34.791439][ C0] ? __pfx_qdisc_graft (net/sched/sch_api.c:1105) 
[ 34.791573][ C0] ? __pfx_qdisc_create (net/sched/sch_api.c:1257) 
[ 34.791712][ C0] tc_modify_qdisc (net/sched/sch_api.c:1789) 
[ 34.791845][ C0] ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 52)) 
[ 34.791975][ C0] ? __pfx_tc_modify_qdisc (net/sched/sch_api.c:1604) 
[ 34.792108][ C0] ? __mutex_lock (./arch/x86/include/asm/preempt.h:94 kernel/locking/mutex.c:618 kernel/locking/mutex.c:752) 
[ 34.792243][ C0] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 34.792393][ C0] rtnetlink_rcv_msg (net/core/rtnetlink.c:6647) 
[ 34.792531][ C0] ? __pfx_rtnetlink_rcv_msg (net/core/rtnetlink.c:6541) 
[ 34.792664][ C0] ? hlock_class (./arch/x86/include/asm/bitops.h:227 ./arch/x86/include/asm/bitops.h:239 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 kernel/locking/lockdep.c:227) 
[ 34.792796][ C0] ? mark_lock (kernel/locking/lockdep.c:4655 (discriminator 3)) 
[ 34.792898][ C0] ? __lock_acquire (kernel/locking/lockdep.c:5142) 
[ 34.793031][ C0] netlink_rcv_skb (net/netlink/af_netlink.c:2550) 
[ 34.793166][ C0] ? __pfx_rtnetlink_rcv_msg (net/core/rtnetlink.c:6541) 
[ 34.793303][ C0] ? __pfx_netlink_rcv_skb (net/netlink/af_netlink.c:2527) 
[ 34.793439][ C0] ? netlink_deliver_tap (./include/linux/rcupdate.h:336 ./include/linux/rcupdate.h:869 net/netlink/af_netlink.c:340) 
[ 34.793576][ C0] ? netlink_deliver_tap (./include/linux/rcupdate.h:336 ./include/linux/rcupdate.h:869 ./include/net/netns/generic.h:48 net/netlink/af_netlink.c:333) 
[ 34.793713][ C0] netlink_unicast (net/netlink/af_netlink.c:1331 net/netlink/af_netlink.c:1357) 
[ 34.793850][ C0] ? __pfx_netlink_unicast (net/netlink/af_netlink.c:1342) 
[ 34.793981][ C0] ? find_held_lock (kernel/locking/lockdep.c:5249) 
[ 34.794117][ C0] netlink_sendmsg (net/netlink/af_netlink.c:1901) 
[ 34.794249][ C0] ? __pfx_netlink_sendmsg (net/netlink/af_netlink.c:1820) 
[ 34.794386][ C0] ? __might_fault (mm/memory.c:6388 mm/memory.c:6381) 
[ 34.794521][ C0] ? __import_iovec (lib/iov_iter.c:1263 lib/iov_iter.c:1279) 
[ 34.794657][ C0] ____sys_sendmsg (net/socket.c:730 net/socket.c:745 net/socket.c:2597) 
[ 34.794801][ C0] ? __pfx_____sys_sendmsg (net/socket.c:2543) 
[ 34.794933][ C0] ? __pfx_copy_msghdr_from_user (net/socket.c:2523) 
[ 34.795097][ C0] ___sys_sendmsg (net/socket.c:2653) 
[ 34.795231][ C0] ? __pfx____sys_sendmsg (net/socket.c:2640) 
[ 34.795370][ C0] ? kfree (mm/slub.c:4583) 
[ 34.795473][ C0] ? ___sys_recvmsg (net/socket.c:2848) 
[ 34.795607][ C0] ? __pfx____sys_recvmsg (net/socket.c:2848) 
[ 34.795744][ C0] ? reacquire_held_locks (kernel/locking/lockdep.c:5284) 
[ 34.795877][ C0] ? do_user_addr_fault (./include/linux/rcupdate.h:326 ./include/linux/rcupdate.h:838 ./include/linux/mm.h:713 arch/x86/mm/fault.c:1340) 
[ 34.796014][ C0] ? __fget_light (./include/linux/atomic/atomic-arch-fallback.h:479 ./include/linux/atomic/atomic-instrumented.h:50 fs/file.c:1145) 
[ 34.796151][ C0] __sys_sendmsg (./include/linux/file.h:34 net/socket.c:2682) 
[ 34.796291][ C0] ? __pfx___sys_sendmsg (net/socket.c:2668) 
[ 34.796426][ C0] ? __pfx___up_read (kernel/locking/rwsem.c:1339) 
[ 34.796564][ C0] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) 
[ 34.796701][ C0] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) 
[   34.796861][    C0] RIP: 0033:0x7fba571567b7
[ 34.797006][ C0] Code: 0a 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b9 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 89 54 24 1c 48 89 74 24 10
All code
========
   0:	0a 00                	or     (%rax),%al
   2:	f7 d8                	neg    %eax
   4:	64 89 02             	mov    %eax,%fs:(%rdx)
   7:	48 c7 c0 ff ff ff ff 	mov    $0xffffffffffffffff,%rax
   e:	eb b9                	jmp    0xffffffffffffffc9
  10:	0f 1f 00             	nopl   (%rax)
  13:	f3 0f 1e fa          	endbr64
  17:	64 8b 04 25 18 00 00 	mov    %fs:0x18,%eax
  1e:	00 
  1f:	85 c0                	test   %eax,%eax
  21:	75 10                	jne    0x33
  23:	b8 2e 00 00 00       	mov    $0x2e,%eax
  28:	0f 05                	syscall
  2a:*	48 3d 00 f0 ff ff    	cmp    $0xfffffffffffff000,%rax		<-- trapping instruction
  30:	77 51                	ja     0x83
  32:	c3                   	ret
  33:	48 83 ec 28          	sub    $0x28,%rsp
  37:	89 54 24 1c          	mov    %edx,0x1c(%rsp)
  3b:	48 89 74 24 10       	mov    %rsi,0x10(%rsp)

Code starting with the faulting instruction
===========================================
   0:	48 3d 00 f0 ff ff    	cmp    $0xfffffffffffff000,%rax
   6:	77 51                	ja     0x59
   8:	c3                   	ret
   9:	48 83 ec 28          	sub    $0x28,%rsp
   d:	89 54 24 1c          	mov    %edx,0x1c(%rsp)
  11:	48 89 74 24 10       	mov    %rsi,0x10(%rsp)
[   34.797481][    C0] RSP: 002b:00007fff8da72d48 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[   34.797688][    C0] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fba571567b7
[   34.797892][    C0] RDX: 0000000000000000 RSI: 00007fff8da72db0 RDI: 0000000000000005
[   34.798136][    C0] RBP: 000000000047d6a0 R08: 0000000000000014 R09: 0000000000000000
[   34.798339][    C0] R10: 00007fba5700f708 R11: 0000000000000246 R12: 00007fff8da83070


Finger prints:
do_raw_spin_unlock:_raw_spin_unlock:net_tx_action:handle_softirqs:do_softirq