[Intel-gfx] [CI 04/20] drm/i915: Remove the dedicated hangcheck workqueue

[Tvrtko Ursulin]

On 20/05/16 13:23, Chris Wilson wrote:
> On Fri, May 20, 2016 at 01:07:29PM +0100, Tvrtko Ursulin wrote:
>>
>> On 19/05/16 14:13, Chris Wilson wrote:
>>> On Thu, May 19, 2016 at 01:50:51PM +0100, Tvrtko Ursulin wrote:
>>>>
>>>> On 19/05/16 12:32, Chris Wilson wrote:
>>>>> The queue only ever contains at most one item and has no special flags.
>>>>> It is just a very simple wrapper around the system-wq - a complication
>>>>> with no benefits.
>>>>
>>>> How much time do we take in the reset case - is it acceptable to do
>>>> that work from the system wq?
>>>
>>> Hangcheck is a handful of register reads and some pointer chasing per
>>> engine. (There is a seqno_barrier in there which may be reasonably
>>> expensive but not a cpu hog). The error capture is run from the
>>> hangcheck context - and that is no small task (especially if we ever
>>> apply the object compression patches), but for safety we need to call
>>> stop_machine() so it really doesn't matter at that point.
>>
>> I don't see a stop_machine? So until there is one, using the system
>> wq is a bit impolite in the error capture state, agreed?
>
> It's in the queue to fix the odd oops we get during capture.
>
> You'd be happy with system_long_wq in the meantime?

Having read the comment in include/linux/workqueue.h I think that would 
be more appropriate in general, so yes.

Regards,

Tvrtko