On 14/01/2016 11:36, Chris Wilson wrote:
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
That what this patch does.
introduce a blocking context-close, nor do you need to introduce the usage of default_context.
The use of default_context here is to stop a context hanging around after it is no longer needed.
(lr_context_pin should take a reference on the ctx to prevent early freeeing ofc).
You can't clear the reference on the ctx in an interrupt context.
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
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