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

Tomas Elf
2015-03-05T18:16:12Z

On 19/02/2015 17:17, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@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@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@intel.com>

Thanks,
Tomas