[Intel-gfx] [PATCH 1/4] drm/i915: Teach hangcheck about long operations on rings

[Chris Wilson]

On Mon, Nov 30, 2015 at 06:53:06PM +0200, Mika Kuoppala wrote:
> Some operations that happen in ringbuffer, like flushing,
> can take significant amounts of time. After some intense
> shader tests, the PIPE_CONTROL with flush can apparently last
> longer time than what is our hangcheck tick (1500ms). If
> this happens twice in a row, even with subsequent batches,
> the hangcheck score decaying mechanism can't cope and
> hang is declared.
> 
> Strip out actual head checking to a separate function and if
> actual head has not moved, check if it is lingering inside the
> ringbuffer as opposed to batch. If so, treat it as if it would be
> inside loop to only slightly increment the hangcheck score.

The PIPE_CONTROL in the ring after the batch, is equivalent to the batch
performing its own PIPE_CONTROL as the last instruction. It does not
make sense to distinguish the two.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre