[Intel-gfx] sw_sync deadlock avoidance, take 3

[Chris Wilson]

Quoting Bas Nieuwenhuizen (2020-07-15 11:23:35)
> Hi Chris,
> 
> My concern with going in this direction was that we potentially allow
> an application to allocate a lot of kernel memory but not a lot of fds
> by creating lots of fences and then closing the fds but never
> signaling them. Is that not an issue?

I did look to see if there was a quick way we could couple into the
sync_file release itself to remove the syncpt from the timeline, but
decided that for a debug feature, it wasn't a pressing concern.

Maybe now is the time to ask: are you using sw_sync outside of
validation?
-Chris