Messages in this thread | | | Date | Wed, 18 Nov 2015 21:37:42 +0100 (CET) | From | Jiri Kosina <> | Subject | Re: [PATCH] hid: usbhid: hid-core: fix recursive deadlock |
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On Wed, 18 Nov 2015, Ioan-Adrian Ratiu wrote:
> The critical section protected by usbhid->lock in hid_ctrl() is too > big and in rare cases causes a recursive deadlock because of its call > to hid_input_report(). > > This deadlock reproduces on newer wacom tablets like 056a:033c because > the wacom driver in its irq handler ends up calling hid_hw_request() > from wacom_intuos_schedule_prox_event() in wacom_wac.c. What this means > is that it submits a report to reschedule a proximity read through a > sync ctrl call which grabs the lock in hid_ctrl(struct urb *urb) > before calling hid_input_report(). When the irq kicks in on the same > cpu, it also tries to grab the lock resulting in a recursive deadlock. > > The proper fix is to shrink the critical section in hid_ctrl() to > protect only the instructions which modify usbhid, thus move the lock > after the hid_input_report() call and the deadlock dissapears.
I think the proper fix actually is to spin_lock_irqsave() in hid_ctrl(), isn't it?
-- Jiri Kosina SUSE Labs
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