[PATCH] i915: Add support for drm syncobjs

[Chris Wilson]

Quoting Jason Ekstrand (2017-08-03 19:06:02)
> I'm not concerned about what happens to racy clients.  They get what they get. 
> What concerns me is what happens if somehow the fence is replaced and deleted
> before i915_gem_request_await_dma_fence takes it's reference.  Can this cause
> the kernel to segfault?

Gotcha, yup nothing prevents that.

	fence = dma_fence_get_rcu_safe(&syncobj->fence);
	if (!fence)
		return -EINVAL;

	err = await_fence();
	dma_fence_put(fence);
	if (err < 0)
		return;

Happy?
-Chris