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

[Tvrtko Ursulin]

On 31/07/2020 16:24, Chris Wilson wrote:
> 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.

In this case I think it is better to avoid changes which can introduce 
potential bugs. (And added bonus time saved on review. :)

Regards,

Tvrtko