Greetings,

I got the below dmesg and the first bad commit is

commit 29ff818720ce09b044652b83e9c70ef474800d54
Author:     Nicholas Bellinger <nab@linux-iscsi.org>
AuthorDate: Thu May 23 22:11:38 2013 -0700
Commit:     Nicholas Bellinger <nab@linux-iscsi.org>
CommitDate: Sun Dec 22 13:00:48 2013 +0000

    scsi-debug: Enable scsi-mq operation
    
    v4 changes:
      - Bump can_queue to 64 for performance testing
      - Enable scsi-mq DIF support
      - Add nop_fs_io module parameter for performance testing
    
    Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

+-----------------------------------------------------+----+
|                                                     |    |
+-----------------------------------------------------+----+
| boot_successes                                      | 0  |
| boot_failures                                       | 19 |
| WARNING:CPU:PID:at_block/elevator.c:elevator_init() | 19 |
+-----------------------------------------------------+----+

[    4.763205]   CPU 1 -> Queue 0
[    4.764566] ------------[ cut here ]------------
[    4.764566] ------------[ cut here ]------------
[    4.765951] WARNING: CPU: 0 PID: 99 at block/elevator.c:193 elevator_init+0xf0/0xfb()

Attached are the full dmesg and kconfig.

Thanks,
Fengguang