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SubjectRe: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning
On Tue, Mar 01, 2016 at 10:07:40AM -0500, Steven Rostedt wrote:
> On Tue, 1 Mar 2016 11:05:42 +0100
> Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
>
> > [ FACT #3: TEST-CASE #2 ]
> >
> > The most reliable test-case is to simply unplug my external Logitech
> > USB mouse - saw this by accident.
> > YES, it was so simple.
>
> Just to clarify, this happens on gcc and clang?

Just clang from what I gather.

> > --- dmesg_4.5.0-rc6-2-llvmlinux-amd64.txt 2016-02-29
> > 21:23:56.399691975 +0100
> > +++ dmesg_4.5.0-rc6-2-llvmlinux-amd64_usbmouse-unplugged.txt
> > 2016-02-29 21:28:14.401832240 +0100
> > @@ -832,3 +832,75 @@
> > [ 66.529779] PPP BSD Compression module registered
> > [ 66.563013] PPP Deflate Compression module registered
> > [ 66.978977] usb 2-1.5: USB disconnect, device number 4
> > +[ 321.937369] usb 2-1.4: USB disconnect, device number 3
> > +[ 321.950810] BUG: sleeping function called from invalid context at
> > kernel/workqueue.c:2785
> > +[ 321.950816] in_atomic(): 0, irqs_disabled(): 1, pid: 44, name: kworker/2:1
> > +[ 321.950819] 9 locks held by kworker/2:1/44:
> > +[ 321.950820] #0: ("usb_hub_wq"){.+.+.+}, at: [<ffffffff810a7c5f>]
> > process_one_work+0x30f/0x8d0
> > +[ 321.950830] #1: ((&hub->events)){+.+.+.}, at:
> > [<ffffffff810a7c8c>] process_one_work+0x33c/0x8d0
> > +[ 321.950836] #2: (&dev->mutex){......}, at: [<ffffffff816fb0e0>]
> > hub_event+0x50/0x15b0
> > +[ 321.950844] #3: (&dev->mutex){......}, at: [<ffffffff816f686f>]
> > usb_disconnect+0x5f/0x2c0
> > +[ 321.950849] #4: (&dev->mutex){......}, at: [<ffffffff816245a2>]
> > device_release_driver+0x22/0x40
> > +[ 321.950856] #5: (&dev->mutex){......}, at: [<ffffffff816245a2>]
> > device_release_driver+0x22/0x40
> > +[ 321.950862] #6: (input_mutex){+.+.+.}, at: [<ffffffff8175171a>]
> > __input_unregister_device+0x9a/0x190
> > +[ 321.950869] #7: (&dev->mutex#2){+.+...}, at:
> > [<ffffffff8174fe27>] input_close_device+0x27/0x70
> > +[ 321.950875] #8: (hid_open_mut){+.+...}, at: [<ffffffffa0057388>]
> > usbhid_close+0x28/0xb0 [usbhid]
> > +[ 321.950883] irq event stamp: 47770
> > +[ 321.950885] hardirqs last enabled at (47769):
> > [<ffffffff819426a2>] _raw_spin_unlock_irq+0x32/0x60
> > +[ 321.950889] hardirqs last disabled at (47770):
> > [<ffffffff81115bdc>] del_timer_sync+0x3c/0x110
>
> According to lockdep, interrupts were last disabled in del_timer_sync,
> and they were never enabled. The numbers in parenthesis show the order
> of events. _raw_spin_unlock_irq() at 47769, then del_timer_sync at
> 47770.
>
> But why did they not get enabled again? We have:
>
> local_irq_save(flags);
> lock_map_acquire(&timer->lockdep_map);
> lock_map_release(&timer->lockdep_map);
> local_irq_restore(flags);
>
> If this caused an issue, then you would have a lockdep splat. But
> perhaps something corrupted "flags", and interrupts were not re-enabled?

Right, most odd. Sedat, could you provide objdump -D of the relevant
sections of vmlinux ?

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