[Intel-gfx] [PATCH] drm/i915: Reduce i915_request.lock contention for i915_request_wait

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-07-16 09:41:17)
> Right I missed dma_fence_is_signaled calls i915_request_completed.
> 
> In this case the remaining question is do we care about wait ioctl 
> potentially returning before the hypothetical sync fence for the same 
> request is signaled? This seems like a slight change in user observable 
> behaviour.

You would not be able to observe the difference after wakeup in state 
between a sync_file and busy_ioctl/wait_ioctl, as a query after wakeup
will see the same signaled bit. So the only possible difference is a
change in wakeup order; but process wakeup/execution order is definitely
not defined by us :)
-Chris