Bluetooth: Fix possible deadlock in btusb

commit 8f9d02f470f48416444ac3a1eacecdd0f743f1a7 introduced spinlocks
in btusb_work. This is run in a context of a worqueue and can be interrupted
by hardware irq. If it happens while spinlock is held, we have a deadlock.
Solution is to use _irqsave/_resore version of locking

[ 466.460560] =================================
[ 466.460565] [ INFO: inconsistent lock state ]
[ 466.460572] 4.3.0-rc6+ #1 Tainted: G W
[ 466.460576] ---------------------------------
[ 466.460582] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
[ 466.460589] kworker/0:2/94 [HC0[0]:SC0[0]:HE1:SE1] takes:
[ 466.460595] (&(&data->rxlock)->rlock){?.-...}, at: [<ffffffffa0526923>] btusb_work+0xa3/0x3fd [btusb]
[ 466.460621] {IN-HARDIRQ-W} state was registered at:
[ 466.460625] [<ffffffff811021b5>] __lock_acquire+0xc45/0x1e80
[ 466.460638] [<ffffffff811040d5>] lock_acquire+0xe5/0x1f0
[ 466.460646] [<ffffffff8182f108>] _raw_spin_lock+0x38/0x50
[ 466.460657] [<ffffffffa0525448>] btusb_recv_intr+0x38/0x170 [btusb]
[ 466.460668] [<ffffffffa0525626>] btusb_intr_complete+0xa6/0x130 [btusb]
[ 466.460679] [<ffffffff815d8f1e>] __usb_hcd_giveback_urb+0x8e/0x160
[ 466.460690] [<ffffffff815d911f>] usb_hcd_giveback_urb+0x3f/0x120
[ 466.460698] [<ffffffff81606e4d>] uhci_giveback_urb+0xad/0x280
[ 466.460706] [<ffffffff81608f64>] uhci_scan_schedule.part.33+0x6b4/0xbe0
[ 466.460714] [<ffffffff81609b50>] uhci_irq+0xd0/0x180
[ 466.460722] [<ffffffff815d8296>] usb_hcd_irq+0x26/0x40
[ 466.460729] [<ffffffff81117d40>] handle_irq_event_percpu+0x40/0x300
[ 466.460739] [<ffffffff81118040>] handle_irq_event+0x40/0x60
[ 466.460746] [<ffffffff8111af39>] handle_fasteoi_irq+0x89/0x150
[ 466.460754] [<ffffffff8101e0f3>] handle_irq+0x73/0x120
[ 466.460763] [<ffffffff81832f11>] do_IRQ+0x61/0x120
[ 466.460772] [<ffffffff8183084c>] ret_from_intr+0x0/0x31
[ 466.460780] [<ffffffff81697a77>] cpuidle_enter+0x17/0x20
[ 466.460790] [<ffffffff810f62c2>] call_cpuidle+0x32/0x60
[ 466.460800] [<ffffffff810f65a8>] cpu_startup_entry+0x2b8/0x3f0
[ 466.460807] [<ffffffff818214ca>] rest_init+0x13a/0x140
[ 466.460817] [<ffffffff81f76029>] start_kernel+0x4a3/0x4c4
[ 466.460827] [<ffffffff81f75339>] x86_64_start_reservations+0x2a/0x2c
[ 466.460837] [<ffffffff81f75485>] x86_64_start_kernel+0x14a/0x16d
[ 466.460846] irq event stamp: 754913
[ 466.460851] hardirqs last enabled at (754913): [<ffffffff8182f4cc>] _raw_spin_unlock_irq+0x2c/0x40
[ 466.460861] hardirqs last disabled at (754912): [<ffffffff8182f28d>] _raw_spin_lock_irq+0x1d/0x60
[ 466.460869] softirqs last enabled at (753024): [<ffffffff810aeaa0>] __do_softirq+0x380/0x490
[ 466.460880] softirqs last disabled at (753009): [<ffffffff810aedef>] irq_exit+0x10f/0x120
[ 466.460888]
other info that might help us debug this:
[ 466.460894] Possible unsafe locking scenario:

[ 466.460899] CPU0
[ 466.460903] ----
[ 466.460907] lock(&(&data->rxlock)->rlock);
[ 466.460915] <Interrupt>
[ 466.460918] lock(&(&data->rxlock)->rlock);
[ 466.460926]
*** DEADLOCK ***

[ 466.460935] 2 locks held by kworker/0:2/94:
[ 466.460939] #0: ("events"){.+.+.+}, at: [<ffffffff810c69bb>] process_one_work+0x16b/0x660
[ 466.460958] #1: ((&data->work)){+.+...}, at: [<ffffffff810c69bb>] process_one_work+0x16b/0x660
[ 466.460974]

Signed-off-by: Kuba Pawlak <[e-mail]>
Signed-off-by: Marcel Holtmann <[e-mail]>

drivers/bluetooth/btusb.c

···
 		}
 
 		if (data->isoc_altsetting != new_alts) {
+			unsigned long flags;
+
 			clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
 			usb_kill_anchored_urbs(&data->isoc_anchor);
 
···
 			 * Clear outstanding fragment when selecting a new
 			 * alternate setting.
 			 */
-			spin_lock(&data->rxlock);
+			spin_lock_irqsave(&data->rxlock, flags);
 			kfree_skb(data->sco_skb);
 			data->sco_skb = NULL;
-			spin_unlock(&data->rxlock);
+			spin_unlock_irqrestore(&data->rxlock, flags);
 
 			if (__set_isoc_interface(hdev, new_alts) < 0)
 				return;