INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
CPU: 1 PID: 1238 Comm: kworker/1:1H Not tainted 4.15.0-rc3-next-20171213+ #66
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: kblockd blk_mq_run_work_fn
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xe9/0x14b lib/dump_stack.c:53
 register_lock_class+0x164/0x5d0 kernel/locking/lockdep.c:752
 __lock_acquire+0xb4/0x1430 kernel/locking/lockdep.c:3314
 lock_acquire+0xbf/0x220 kernel/locking/lockdep.c:3914
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:144
 spin_lock include/linux/spinlock.h:310 [inline]
 blk_mq_sched_dispatch_requests+0x9d/0x1f0 block/blk-mq-sched.c:194
 __blk_mq_run_hw_queue+0x160/0x220 block/blk-mq.c:1219
 blk_mq_run_work_fn+0x3f/0x50 block/blk-mq.c:1424
 process_one_work+0x288/0x7a0 kernel/workqueue.c:2112
 worker_thread+0x43/0x4d0 kernel/workqueue.c:2246
 kthread+0x149/0x170 kernel/kthread.c:238
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: list_splice_init include/linux/list.h:337 [inline]
IP: blk_mq_sched_dispatch_requests+0xc5/0x1f0 block/blk-mq-sched.c:196
PGD 1e3a64067 P4D 1e3a64067 PUD 1e3a58067 PMD 0 
Oops: 0002 [#1] SMP
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 1238 Comm: kworker/1:1H Not tainted 4.15.0-rc3-next-20171213+ #66
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: kblockd blk_mq_run_work_fn
RIP: 0010:list_splice_init include/linux/list.h:337 [inline]
RIP: 0010:blk_mq_sched_dispatch_requests+0xc5/0x1f0 block/blk-mq-sched.c:196
RSP: 0018:ffffc90002aa3dc8 EFLAGS: 00010293
RAX: ffffc90002aa3dc8 RBX: ffff8801e4b3fc00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801e4b3fc00
RBP: ffffc90002aa3e00 R08: 0000000000000000 R09: ffffffff816fdacd
R10: ffffc90002aa3d38 R11: 0000000000000000 R12: ffffc90002aa3dc8
R13: ffff8801e4b3fc38 R14: ffff8802156b4b10 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 00000001e05c7000 CR4: 00000000001426e0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 __blk_mq_run_hw_queue+0x160/0x220 block/blk-mq.c:1219
 blk_mq_run_work_fn+0x3f/0x50 block/blk-mq.c:1424
 process_one_work+0x288/0x7a0 kernel/workqueue.c:2112
 worker_thread+0x43/0x4d0 kernel/workqueue.c:2246
 kthread+0x149/0x170 kernel/kthread.c:238
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
Code: 05 ed 00 48 8b 43 38 49 39 c5 74 36 e8 95 c8 bb ff 48 8b 43 38 49 39 c5 74 28 e8 87 c8 bb ff 48 8b 4b 38 48 8b 53 40 48 8b 45 c8 <4c> 89 61 08 48 89 4d c8 48 89 02 48 89 50 08 4c 89 6b 38 4c 89 
RIP: list_splice_init include/linux/list.h:337 [inline] RSP: ffffc90002aa3dc8
RIP: blk_mq_sched_dispatch_requests+0xc5/0x1f0 block/blk-mq-sched.c:196 RSP: ffffc90002aa3dc8
CR2: 0000000000000008
---[ end trace 9b5ad1627577b3ca ]---