[Intel-gfx] [PATCH 02/11] drm/i915: Only reset hangcheck at the start of an activity cycle

[Chris Wilson]

Quoting Mika Kuoppala (2018-07-09 15:13:44)
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > Across a reset, the seqno (and thus hangcheck) should restart and the
> > hangcheck naturally progress, for when it does not, we want to declare an
> > emergency. Currently, we only detect if reset and reinit fails, but we
> > do not detect if the call to reinit succeeds but the HW is fried - as we
> > are resetting hangcheck on initialisation the engine. Remove that and
> > rely on the natural progress to reset the hangcheck timer.
> 
> I take it that the intention is not to give reset
> any special leeway wrt to request completion. So
> we now assume that reset/recovery must fit inside
> one hangcheck tick?

We call the synchronous i915_handle_error() from inside hangcheck, so we
know the reset is completed before we schedule the next tick. So yes it
seems fair that the recovery should always be expected to complete
within that tick as we would expect any other batch to complete (and the
recovery request is just to advance the breadcrumb, no batch).

So yes, reset/recovery must fit inside the tick.
-Chris