Re: [PATCH] hid: usbhid: hid-core: fix recursive deadlock

Jiri Kosina
2015-11-19T09:11:07Z

On Thu, 19 Nov 2015, Ioan-Adrian Ratiu wrote:

> First part of lockdep report:
> http://imgur.com/clLsCWe
>
> Second part:
> http://imgur.com/Wa2PzRl
>
> Here are some printk's of mine while reproducing + debugging the issue:
> http://imgur.com/SETOHT7

So the real problem is that Intuos driver is calling hid_hw_request()
(which tries to grab the lock in usbhid_submit_report()) while handling
the CTRL IRQ (lock gets acquired there).

So the proper way to fix seems to be delaying the scheduling of the
proximity read event in wacom_intuos_inout() to workqueue.

> I'll continue to research this more in depth, but progress is slow
> because I don't have much time, I'm doing this in my spare time because
> it's my girlfriend's tablet.

Oh, now I understand the level of severity of this bug! :-)

Thanks,

--
Jiri Kosina
SUSE Labs