[Intel-gfx] [PATCH 17/21] drm/i915/gt: Protect context lifetime with RCU

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-07-31 16:15:43)
> 
> On 30/07/2020 10:37, Chris Wilson wrote:
> > Allow a brief period for continued access to a dead intel_context by
> > deferring the release of the struct until after an RCU grace period.
> > As we are using a dedicated slab cache for the contexts, we can defer
> > the release of the slab pages via RCU, with the caveat that individual
> > structs may be reused from the freelist within an RCU grace period. To
> > handle that, we have to avoid clearing members of the zombie struct.
> 
> What was the motivation?

I wanted a window where the pointer was kept alive by RCU after we
called intel_context_put() so I could keep using spinlock for a bit.

If you look closely, you might spot that isn't used any more, but I
liked the ctor so kept it around.
-Chris