On Wed, Jan 13, 2016 at 04:19:45PM +0000, Nick Hoath wrote:
> + if (ctx->engine[ring->id].dirty) {
> + struct drm_i915_gem_request *req = NULL;
> +
> + /**
> + * If there is already a request pending on
> + * this ring, wait for that to complete,
> + * otherwise create a switch to idle request
> + */
> + if (list_empty(&ring->request_list)) {
> + int ret;
> +
> + ret = i915_gem_request_alloc(
> + ring,
> + ring->default_context,
> + &req);
> + if (!ret)
> + i915_add_request(req);
> + else
> + DRM_DEBUG("Failed to ensure context saved");
> + } else {
> + req = list_first_entry(
> + &ring->request_list,
> + typeof(*req), list);
> + }
> + if (req) {
> + ret = i915_wait_request(req);
> + if (ret != 0) {
> + /**
> + * If we get here, there's probably been a ring
> + * reset, so we just clean up the dirty flag.&
> + * pin count.
> + */
> + ctx->engine[ring->id].dirty = false;
> + __intel_lr_context_unpin(
> + ring,
> + ctx);
> + }
> + }
If you were to take a lr_context_pin on the last_context, and only
release that pin when you change to a new context, you do not need to
introduce a blocking context-close, nor do you need to introduce the
usage of default_context.
(lr_context_pin should take a reference on the ctx to prevent early
freeeing ofc).
The code at that point starts to look v.v.similar to legacy, right down
to the need to use a GPU reset during shutdown to prevent writing back
the context image. (Which you still currently need to get rid of the
default context now.)
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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