Bluetooth: Fix potential deadlock in mgmt

All threads running in process context should disable local bottom
halve before locking hdev->lock.

This patch fix the following message generated when Bluetooh module
is loaded with enable_mgmt=y (CONFIG_PROVE_LOCKING enabled).

[  107.880781] =================================
[  107.881631] [ INFO: inconsistent lock state ]
[  107.881631] 2.6.39+ #1
[  107.881631] ---------------------------------
[  107.881631] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[  107.881631] rcuc0/7 [HC0[0]:SC1[3]:HE1:SE0] takes:
[  107.881631]  (&(&hdev->lock)->rlock){+.?...}, at: [<ffffffffa0012c8d>] mgmt_set_local_name_complete+0x84/0x10b [bluetooth]
[  107.881631] {SOFTIRQ-ON-W} state was registered at:
[  107.881631]   [<ffffffff8105188b>] __lock_acquire+0x347/0xd52
[  107.881631]   [<ffffffff810526ac>] lock_acquire+0x8a/0xa7
[  107.881631]   [<ffffffff812b3758>] _raw_spin_lock+0x2c/0x3b
[  107.881631]   [<ffffffffa0011cc2>] mgmt_control+0xd4d/0x175b [bluetooth]
[  107.881631]   [<ffffffffa0013275>] hci_sock_sendmsg+0x97/0x293 [bluetooth]
[  107.881631]   [<ffffffff8121940c>] sock_aio_write+0x126/0x13a
[  107.881631]   [<ffffffff810a35fa>] do_sync_write+0xba/0xfa
[  107.881631]   [<ffffffff810a3beb>] vfs_write+0xaa/0xca
[  107.881631]   [<ffffffff810a3d80>] sys_write+0x45/0x69
[  107.881631]   [<ffffffff812b4892>] system_call_fastpath+0x16/0x1b
[  107.881631] irq event stamp: 2100876
[  107.881631] hardirqs last  enabled at (2100876): [<ffffffff812b40d4>] restore_args+0x0/0x30
[  107.881631] hardirqs last disabled at (2100875): [<ffffffff812b3f6a>] save_args+0x6a/0x70
[  107.881631] softirqs last  enabled at (2100862): [<ffffffff8106a805>] rcu_cpu_kthread+0x2b5/0x2e2
[  107.881631] softirqs last disabled at (2100863): [<ffffffff812b56bc>] call_softirq+0x1c/0x26
[  107.881631]
[  107.881631] other info that might help us debug this:
[  107.881631]  Possible unsafe locking scenario:
[  107.881631]
[  107.881631]        CPU0
[  107.881631]        ----
[  107.881631]   lock(&(&hdev->lock)->rlock);
[  107.881631]   <Interrupt>
[  107.881631]     lock(&(&hdev->lock)->rlock);
[  107.881631]
[  107.881631]  *** DEADLOCK ***
[  107.881631]
[  107.881631] 1 lock held by rcuc0/7:
[  107.881631]  #0:  (hci_task_lock){++.-..}, at: [<ffffffffa0008353>] hci_rx_task+0x49/0x2f3 [bluetooth]
[  107.881631]
[  107.881631] stack backtrace:
[  107.881631] Pid: 7, comm: rcuc0 Not tainted 2.6.39+ #1
[  107.881631] Call Trace:
[  107.881631]  <IRQ>  [<ffffffff812ae901>] print_usage_bug+0x1e7/0x1f8
[  107.881631]  [<ffffffff8100a796>] ? save_stack_trace+0x27/0x44
[  107.881631]  [<ffffffff8104fc3f>] ? print_irq_inversion_bug.part.26+0x19a/0x19a
[  107.881631]  [<ffffffff810504bb>] mark_lock+0x106/0x258
[  107.881631]  [<ffffffff81051817>] __lock_acquire+0x2d3/0xd52
[  107.881631]  [<ffffffff8102be73>] ? vprintk+0x3ab/0x3d7
[  107.881631]  [<ffffffff810526ac>] lock_acquire+0x8a/0xa7
[  107.881631]  [<ffffffffa0012c8d>] ? mgmt_set_local_name_complete+0x84/0x10b [bluetooth]
[  107.881631]  [<ffffffff81052615>] ? lock_release+0x16c/0x179
[  107.881631]  [<ffffffff812b3952>] _raw_spin_lock_bh+0x31/0x40
[  107.881631]  [<ffffffffa0012c8d>] ? mgmt_set_local_name_complete+0x84/0x10b [bluetooth]
[  107.881631]  [<ffffffffa0012c8d>] mgmt_set_local_name_complete+0x84/0x10b [bluetooth]
[  107.881631]  [<ffffffffa000d3fe>] hci_event_packet+0x122b/0x3e12 [bluetooth]
[  107.881631]  [<ffffffff81050658>] ? mark_held_locks+0x4b/0x6d
[  107.881631]  [<ffffffff812b3cff>] ? _raw_spin_unlock_irqrestore+0x40/0x4d
[  107.881631]  [<ffffffff810507b9>] ? trace_hardirqs_on_caller+0x13f/0x172
[  107.881631]  [<ffffffff812b3d07>] ? _raw_spin_unlock_irqrestore+0x48/0x4d
[  107.881631]  [<ffffffffa00083d2>] hci_rx_task+0xc8/0x2f3 [bluetooth]
[  107.881631]  [<ffffffff8102f836>] ? __local_bh_enable+0x90/0xa4
[  107.881631]  [<ffffffff8102f5a9>] tasklet_action+0x87/0xe6
[  107.881631]  [<ffffffff8102fa11>] __do_softirq+0x9f/0x13f
[  107.881631]  [<ffffffff812b56bc>] call_softirq+0x1c/0x26
[  107.881631]  <EOI>  [<ffffffff810033b8>] ? do_softirq+0x46/0x9a
[  107.881631]  [<ffffffff8106a805>] ? rcu_cpu_kthread+0x2b5/0x2e2
[  107.881631]  [<ffffffff8102f906>] _local_bh_enable_ip+0xac/0xc9
[  107.881631]  [<ffffffff8102f93b>] local_bh_enable+0xd/0xf
[  107.881631]  [<ffffffff8106a805>] rcu_cpu_kthread+0x2b5/0x2e2
[  107.881631]  [<ffffffff81041586>] ? __init_waitqueue_head+0x46/0x46
[  107.881631]  [<ffffffff8106a550>] ? rcu_yield.constprop.42+0x98/0x98
[  107.881631]  [<ffffffff81040f0a>] kthread+0x7f/0x87
[  107.881631]  [<ffffffff812b55c4>] kernel_thread_helper+0x4/0x10
[  107.881631]  [<ffffffff812b40d4>] ? retint_restore_args+0x13/0x13
[  107.881631]  [<ffffffff81040e8b>] ? __init_kthread_worker+0x53/0x53
[  107.881631]  [<ffffffff812b55c0>] ? gs_change+0x13/0x13
Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>