[Intel-gfx] [PATCH 02/34] drm/i915/execlists: Suppress preempting self

[John Harrison]

On 1/21/2019 14:20, Chris Wilson wrote:
> In order to avoid preempting ourselves, we currently refuse to schedule
> the tasklet if we reschedule an inflight context. However, this glosses
> over a few issues such as what happens after a CS completion event and
> we then preempt the newly executing context with itself, or if something
> else causes a tasklet_schedule triggering the same evaluation to
> preempt the active context with itself.
>
> To avoid the extra complications, after deciding that we have
> potentially queued a request with higher priority than the currently
> executing request, inspect the head of the queue to see if it is indeed
> higher priority from another context.
>
> References: a2bf92e8cc16 ("drm/i915/execlists: Avoid kicking priority on the current context")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Can you explain what was wrong with the previous version of this patch 
(drm/i915/execlists: Store the highest priority context)? It seemed simpler.

John.