Re: [PATCH 07/59] drm/i915: Early alloc request in execbuff

[Tomas Elf <tomas.elf@intel.com>]

On 19/03/2015 12:30, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
>
> Start of explicit request management in the execbuffer code path. This patch
> adds a call to allocate a request structure before all the actual hardware work
> is done. Thus guaranteeing that all that work is tagged by a known request. At
> present, nothing further is done with the request, the rest comes later in the
> series.
>
> The only noticable change is that failure to get a request (e.g. due to lack of
> memory) will be caught earlier in the sequence. It now occurs right at the start
> before any un-undoable work has been done.
>
> v2: Simplified the error handling path.
>
> For: VIZ-5115
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem_execbuffer.c |    7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 1bb237c..2504cfd 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -1594,10 +1594,16 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
>   	} else
>   		exec_start += i915_gem_obj_offset(batch_obj, vm);
>
> +	/* Allocate a request for this batch buffer nice and early. */
> +	ret = i915_gem_request_alloc(ring, ctx);
> +	if (ret)
> +		goto err_batch_unpin;
> +
>   	ret = dev_priv->gt.execbuf_submit(dev, file, ring, ctx, args,
>   					  &eb->vmas, batch_obj, exec_start,
>   					  dispatch_flags);
>
> +err_batch_unpin:
>   	/*
>   	 * FIXME: We crucially rely upon the active tracking for the (ppgtt)
>   	 * batch vma for correctness. For less ugly and less fragility this
> @@ -1606,6 +1612,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
>   	 */
>   	if (dispatch_flags & I915_DISPATCH_SECURE)
>   		i915_gem_object_ggtt_unpin(batch_obj);
> +
>   err:
>   	/* the request owns the ref now */
>   	i915_gem_context_unreference(ctx);
>

Reviewed-by: Tomas Elf <tomas.elf@intel.com>

Thanks,
Tomas
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