[Intel-gfx] [PATCH] drm/i915/gem: Perform all asynchronous waits prior to marking payload start

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> The initial breadcrumb marks the transition from context wait and setup
> into the request payload. We use the marker to determine if the request
> is merely waiting to begin, or is inside the payload and hung.
> Forgetting to include a breadcrumb before the user payload would mean we
> do not reset the guilty user request, and conversely if the initial
> breadcrumb is too early we blame the user for a problem elsewhere.

Agreed.

>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_client_blt.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c b/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
> index 272cf3ea68d5..44821d94544f 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
> @@ -202,12 +202,6 @@ static void clear_pages_worker(struct work_struct *work)
>  	if (unlikely(err))
>  		goto out_request;
>  
> -	if (w->ce->engine->emit_init_breadcrumb) {
> -		err = w->ce->engine->emit_init_breadcrumb(rq);
> -		if (unlikely(err))
> -			goto out_request;
> -	}
> -
>  	/*
>  	 * w->dma is already exported via (vma|obj)->resv we need only
>  	 * keep track of the GPU activity within this vma/request, and
> @@ -217,9 +211,15 @@ static void clear_pages_worker(struct work_struct *work)
>  	if (err)
>  		goto out_request;
>  
> -	err = w->ce->engine->emit_bb_start(rq,
> -					   batch->node.start, batch->node.size,
> -					   0);

We don't have to do any extra steps to counter

__i915_vma_move_to_active(vma, rq);

in error path?

-Mika

> +	if (rq->engine->emit_init_breadcrumb) {
> +		err = rq->engine->emit_init_breadcrumb(rq);
> +		if (unlikely(err))
> +			goto out_request;
> +	}
> +
> +	err = rq->engine->emit_bb_start(rq,
> +					batch->node.start, batch->node.size,
> +					0);
>  out_request:
>  	if (unlikely(err)) {
>  		i915_request_set_error_once(rq, err);
> -- 
> 2.20.1
>
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