FYI, we noticed the below changes on

git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/urgent
commit ef9db2383c74a9cc0f7f4e0ec2740c865f6532d9 ("lockdep: Fix module unload")


+----------------------------------------------------+----------+------------+
|                                                    | v4.0-rc4 | ef9db2383c |
+----------------------------------------------------+----------+------------+
| boot_successes                                     | 104      | 0          |
| boot_failures                                      | 4        | 10         |
| BUG:kernel_boot_hang                               | 4        |            |
| WARNING:at_kernel/locking/lockdep.c:#check_flags() | 0        | 10         |
| backtrace:rcu_read_lock_held                       | 0        | 10         |
| backtrace:lockdep_init_map                         | 0        | 10         |
| backtrace:__alloc_workqueue_key                    | 0        | 10         |
| backtrace:init_workqueues                          | 0        | 10         |
| backtrace:kernel_init_freeable                     | 0        | 10         |
+----------------------------------------------------+----------+------------+


[    0.039021] Performance Events: Broken PMU hardware detected, using software events only.
[    0.041003] Failed to access perfctr msr (MSR c1 is 0)
[    0.043211] ------------[ cut here ]------------
[    0.043778] WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:3538 check_flags+0x22d/0x240()
[    0.044000] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)
[    0.044000] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.0.0-rc4-01920-g5d82bf5 #278
[    0.044000]  ffffffff82136e10 ffff88001495bb88 ffffffff81da3073 000000000000002e
[    0.044000]  ffff88001495bbd8 ffff88001495bbc8 ffffffff810d1e0b 0000000000000286
[    0.044000]  ffffffff82441420 0000000000000046 ffffffff827c53f1 ffff88001496e850
[    0.044000] Call Trace:
[    0.044000]  [<ffffffff81da3073>] dump_stack+0x4f/0x7b
[    0.044000]  [<ffffffff810d1e0b>] warn_slowpath_common+0x7b/0xc0
[    0.044000]  [<ffffffff810d1eb1>] warn_slowpath_fmt+0x41/0x50
[    0.044000]  [<ffffffff810f7941>] ? get_parent_ip+0x11/0x50
[    0.044000]  [<ffffffff8111659d>] check_flags+0x22d/0x240
[    0.044000]  [<ffffffff81117636>] lock_is_held+0x36/0x90
[    0.044000]  [<ffffffff81129ce5>] rcu_read_lock_held+0x65/0x70
[    0.044000]  [<ffffffff81117d16>] lockdep_init_map+0x336/0x6f0
[    0.044000]  [<ffffffff810ea82f>] alloc_unbound_pwq+0x26f/0x4d0
[    0.044000]  [<ffffffff810eb484>] apply_workqueue_attrs+0x154/0x490
[    0.044000]  [<ffffffff810ebf44>] __alloc_workqueue_key+0x1c4/0x610
[    0.044000]  [<ffffffff81661368>] ? alloc_cpumask_var_node+0x48/0x80
[    0.044000]  [<ffffffff826554d8>] init_workqueues+0x414/0x528
[    0.044000]  [<ffffffff826550c4>] ? wq_sysfs_init+0x14/0x14
[    0.044000]  [<ffffffff826550c4>] ? wq_sysfs_init+0x14/0x14
[    0.044000]  [<ffffffff82640071>] do_one_initcall+0xe8/0x17f
[    0.044000]  [<ffffffff8264c55a>] ? native_smp_prepare_cpus+0x2c0/0x2cf
[    0.044000]  [<ffffffff8264017c>] kernel_init_freeable+0x74/0x1b0
[    0.044000]  [<ffffffff81d973e0>] ? rest_init+0x140/0x140
[    0.044000]  [<ffffffff81d973e9>] kernel_init+0x9/0xf0
[    0.044000]  [<ffffffff81db4943>] ret_from_fork+0x53/0x90
[    0.044000]  [<ffffffff81d973e0>] ? rest_init+0x140/0x140
[    0.044000] ---[ end trace c79ceaf7cc379335 ]---
[    0.044000] possible reason: unannotated irqs-off.



Thanks,
Ying Huang