[Intel-gfx] [PATCH 07/10] drm/i915/execlists: Cancel banned contexts on schedule-out

[Chris Wilson]

Quoting Tvrtko Ursulin (2019-10-11 10:47:26)
> 
> On 10/10/2019 08:14, Chris Wilson wrote:
> > On completion of a banned context, scrub the context image so that we do
> 
> s/completion/schedule out/ like in the subject line? Otherwise I 
> struggle to understand how banned context is completing. Presumably it 
> was banned because it keeps hanging.

Ok, I had the CS completion event in mind, but i915_request_completed()
does muddle the waters.
 
> > not replay the active payload. The intent is that we skip banned
> > payloads on request submission so that the timeline advancement
> > continues on in the background. However, if we are returning to a
> > preempted request, i915_request_skip() is ineffective and instead we
> > need to patch up the context image so that it continues from the start
> > of the next request.
> 
> But if the context is banned why do we want to continue from the start 
> of the next request? Don't we want to zap all submitted so far?

We scrub the payload, but the request itself is still a vital part of
the web of dependencies. That is we still execute the semaphores and
breadcrumbs of the cancelled requests to maintain global ordering.
-Chris