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

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