[Intel-gfx] [PATCH 22/43] drm/i915: Introduce intel_context.pin_mutex for pin management

[Chris Wilson]

Quoting Tvrtko Ursulin (2019-03-06 14:43:13)
> 
> On 06/03/2019 14:24, Chris Wilson wrote:
> > Introduce a mutex to start locking the HW contexts independently of
> > struct_mutex, with a view to reducing the coarse struct_mutex. The
> > intel_context.pin_mutex is used to guard the transition to and from being
> > pinned on the gpu, and so is required before starting to build any
> > request. The intel_context will then remain pinned until the request
> > completes, but the mutex can be released immediately unpin completion of
> > pinning the context.
> > 
> > A slight variant of the above is used by per-context sseu that wants to
> > inspect the pinned status of the context, and requires that it remains
> > stable (either !pinned or pinned) across its operation. By using the
> > pin_mutex to serialise operations while pin_count==0, we can take that
> > pin_mutex for stabilise the boolean pin status.
> 
> Change log!

v2: no code changes, or at least I can only remember rewriting the
commitmsg, so see above.
-Chris