[Intel-gfx] [PATCH] drm/i915/preemption: Allow preemption between submission ports

[Chris Wilson]

Quoting Chris Wilson (2018-02-22 14:22:29)
> Sometimes we need to boost the priority of an in-flight request, which
> may lead to the situation where the second submission port then contains
> a higher priority context than the first and so we need to inject a
> preemption event. To do so we must always check inside
> execlists_dequeue() whether there is a priority inversion between the
> ports themselves as well as the head of the priority sorted queue, and we
> cannot just skip dequeuing if the queue is empty.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Michał Winiarski <michal.winiarski at intel.com>
> Cc: Michel Thierry <michel.thierry at intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Note this probably merits a Fixes tag. Outside of igt causing priority
inversion between GPU hogs, is it a big enough problem to deserve
sending to stable@?
-Chris