I didn't even know I still had lockdep on.
The following lockdep splat happened when I plugged in a usb bluetooth dongle, using
the pre-rc1 3.11 kernel at HEAD b2c311075db
=================================
[ INFO: inconsistent lock state ]
3.10.0+ #106 Not tainted
---------------------------------
inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
irq/42-xhci_hcd/97 [HC0[0]:SC0[2]:HE1:SE0] takes:
(hcd_urb_list_lock){?.....}, at: [<ffffffff8149440e>] usb_hcd_unlink_urb_from_ep+0x28/0x4e
{IN-HARDIRQ-W} state was registered at:
[<ffffffff810afbc6>] __lock_acquire+0x861/0x1c2e
[<ffffffff810b1556>] lock_acquire+0x87/0x139
[<ffffffff81698a1a>] _raw_spin_lock+0x3b/0x4a
[<ffffffff8149440e>] usb_hcd_unlink_urb_from_ep+0x28/0x4e
[<ffffffff814a65f1>] ehci_urb_done+0x5b/0x9c
[<ffffffff814a8e18>] qh_completions+0x311/0x3ca
[<ffffffff814aa613>] ehci_handle_intr_unlinks+0xad/0x143
[<ffffffff814a7098>] ehci_hrtimer_func+0x6b/0xbd
[<ffffffff8107cfc8>] __run_hrtimer+0x61/0x1f9
[<ffffffff8107d7ca>] hrtimer_interrupt+0x10a/0x253
[<ffffffff810256c0>] local_apic_timer_interrupt+0x38/0x5e
[<ffffffff81025ab5>] smp_apic_timer_interrupt+0x46/0x5b
[<ffffffff816a152f>] apic_timer_interrupt+0x6f/0x80
irq event stamp: 224
hardirqs last enabled at (224): [<ffffffff8168e8d4>] __slab_free+0x1c7/0x2ed
hardirqs last disabled at (223): [<ffffffff8168e846>] __slab_free+0x139/0x2ed
softirqs last enabled at (206): [<ffffffff810d8024>] irq_forced_thread_fn+0x49/0x5a
softirqs last disabled at (212): [<ffffffff810d7fff>] irq_forced_thread_fn+0x24/0x5a
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(hcd_urb_list_lock);
<Interrupt>
lock(hcd_urb_list_lock);
*** DEADLOCK ***
1 lock held by irq/42-xhci_hcd/97:
#0: (&(&xhci->lock)->rlock){+.-...}, at: [<ffffffff814befdd>] xhci_irq+0x2f/0x143d
stack backtrace:
CPU: 1 PID: 97 Comm: irq/42-xhci_hcd Not tainted 3.10.0+ #106
Hardware name: Acer Aspire M3985/Aspire M3985, BIOS P01-A1 03/12/2012
ffffffff8210c150 ffff88040834da48 ffffffff81691af4 0000000000000007
ffff8804082e20b0 ffff88040834daa8 ffffffff8168cb10 0000000000000002
ffff880400000001 ffff880400000000 ffffffff8100f4f7 ffff88040834dac4
Call Trace:
[<ffffffff81691af4>] dump_stack+0x4f/0x84
[<ffffffff8168cb10>] print_usage_bug+0x1f5/0x206
[<ffffffff8100f4f7>] ? save_stack_trace+0x2f/0x50
[<ffffffff810af30c>] mark_lock+0x276/0x2cf
[<ffffffff810ae8cc>] ? check_usage_forwards+0x12f/0x12f
[<ffffffff810af925>] __lock_acquire+0x5c0/0x1c2e
[<ffffffff810b1e04>] ? mark_held_locks+0x6d/0x117
[<ffffffff8168e8d4>] ? __slab_free+0x1c7/0x2ed
[<ffffffff810b1f5a>] ? trace_hardirqs_on_caller+0xac/0x1bb
[<ffffffff810b2076>] ? trace_hardirqs_on+0xd/0xf
[<ffffffff8149440e>] ? usb_hcd_unlink_urb_from_ep+0x28/0x4e
[<ffffffff810b1556>] lock_acquire+0x87/0x139
[<ffffffff8149440e>] ? usb_hcd_unlink_urb_from_ep+0x28/0x4e
[<ffffffff81698a1a>] _raw_spin_lock+0x3b/0x4a
[<ffffffff8149440e>] ? usb_hcd_unlink_urb_from_ep+0x28/0x4e
[<ffffffff8149440e>] usb_hcd_unlink_urb_from_ep+0x28/0x4e
[<ffffffff814bf55a>] xhci_irq+0x5ac/0x143d
[<ffffffff81699171>] ? _raw_spin_unlock_irq+0x3b/0x5d
[<ffffffff8108386d>] ? finish_task_switch+0x7c/0x101
[<ffffffff81083830>] ? finish_task_switch+0x3f/0x101
[<ffffffff81697060>] ? __schedule+0x42a/0x885
[<ffffffff810d7fdb>] ? irq_thread_fn+0x48/0x48
[<ffffffff814c03fc>] xhci_msi_irq+0x11/0x15
[<ffffffff810d8009>] irq_forced_thread_fn+0x2e/0x5a
[<ffffffff810d7d36>] irq_thread+0x10e/0x131
[<ffffffff810d7ee3>] ? irq_finalize_oneshot.part.33+0xe0/0xe0
[<ffffffff810d7c28>] ? wake_threads_waitq+0x44/0x44
[<ffffffff81079b61>] kthread+0xea/0xef
[<ffffffff81079a77>] ? flush_kthread_work+0x19c/0x19c
[<ffffffff816a082c>] ret_from_fork+0x7c/0xb0
[<ffffffff81079a77>] ? flush_kthread_work+0x19c/0x19c
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