[Intel-gfx] [PATCH 01/13] drm/i915: Assert breadcrumbs are correctly ordered in the signal handler

[Tvrtko Ursulin]

On 03/05/2019 12:52, Chris Wilson wrote:
> Inside the signal handler, we expect the requests to be ordered by their
> breadcrumb such that no later request may be complete if we find an
> earlier incomplete. Add an assert to check that the next breadcrumb
> should not be logically before the current.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
> index 3cbffd400b1b..a6ffb25f72a2 100644
> --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
> @@ -99,6 +99,12 @@ void intel_engine_breadcrumbs_irq(struct intel_engine_cs *engine)
>   			struct i915_request *rq =
>   				list_entry(pos, typeof(*rq), signal_link);
>   
> +			GEM_BUG_ON(next != &ce->signals &&
> +				   i915_seqno_passed(rq->fence.seqno,
> +						     list_entry(next,
> +								typeof(*rq),
> +								signal_link)->fence.seqno));

I know its only GEM_BUG_ON, but why check for this in the irq handler? 
You don't trust the insertion, or group deletion? Or just becuase it is 
the smallest amount of code to piggy-back on existing iteration?

Regards,

Tvrtko

> +
>   			if (!__request_completed(rq))
>   				break;
>   
>