[Intel-gfx] [PATCH 24/53] drm/i915: Update deferred context creation to do explicit request management

[Tomas Elf]

On 19/02/2015 17:17, John.C.Harrison at Intel.com wrote:
> From: John Harrison <John.C.Harrison at Intel.com>
>
> In execlist mode, context initialisation is deferred until first use of the
> given context. This is because execlist mode has many more contexts than legacy
> mode and many are never actually used. Previously, the initialisation commands
> were written to the ring and tagged with some random request structure via the
> OLR. This seemed to be causing a null pointer deference bug under certain
> circumstances (BZ:40112).
>
> This patch adds explicit request creation and submission to the deferred
> initialisation code path. Thus removing any reliance on or randomness caused by
> the OLR.
>
> For: VIZ-5115
> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
> ---
>   drivers/gpu/drm/i915/intel_lrc.c |   17 ++++++++++++++++-
>   1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index dff7829..4bcb70e 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -1849,6 +1849,7 @@ static void lrc_setup_hardware_status_page(struct intel_engine_cs *ring,
>   int intel_lr_context_deferred_create(struct intel_context *ctx,
>   				     struct intel_engine_cs *ring)
>   {
> +	struct drm_i915_private *dev_priv = ring->dev->dev_private;
>   	const bool is_global_default_ctx = (ctx == ring->default_context);
>   	struct drm_device *dev = ring->dev;
>   	struct drm_i915_gem_object *ctx_obj;
> @@ -1929,13 +1930,27 @@ int intel_lr_context_deferred_create(struct intel_context *ctx,
>   		lrc_setup_hardware_status_page(ring, ctx_obj);
>   	else if (ring->id == RCS && !ctx->rcs_initialized) {
>   		if (ring->init_context) {
> -			ret = ring->init_context(ring, ctx);
> +			struct drm_i915_gem_request *req;
> +
> +			ret = dev_priv->gt.alloc_request(ring, ctx, &req);
> +			if (ret)
> +				return ret;
> +
> +			ret = ring->init_context(req->ring, ctx);
>   			if (ret) {
>   				DRM_ERROR("ring init context: %d\n", ret);
> +				i915_gem_request_unreference(req);
>   				ctx->engine[ring->id].ringbuf = NULL;
>   				ctx->engine[ring->id].state = NULL;
>   				goto error;
>   			}
> +
> +			ret = i915_add_request_no_flush(req->ring);
> +			if (ret) {
> +				DRM_ERROR("ring init context: %d\n", ret);
> +				i915_gem_request_unreference(req);
> +				goto error;
> +			}
>   		}
>
>   		ctx->rcs_initialized = true;
>

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

Thanks,
Tomas