[Intel-gfx] [PATCH v6 09/11] drm/i915/perf: allow holding preemption on filtered ctx

[Chris Wilson]

Quoting Lionel Landwerlin (2019-07-01 13:10:53)
> On 01/07/2019 15:03, Chris Wilson wrote:
> > Quoting Lionel Landwerlin (2019-07-01 12:34:35)
> >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> >> index f92bace9caff..012d6d7f54e2 100644
> >> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> >> @@ -2104,6 +2104,14 @@ static int eb_oa_config(struct i915_execbuffer *eb)
> >>          if (err)
> >>                  return err;
> >>   
> >> +       /*
> >> +        * If the perf stream was opened with hold preemption, flag the
> >> +        * request properly so that the priority of the request is bumped once
> >> +        * it reaches the execlist ports.
> >> +        */
> >> +       if (eb->i915->perf.oa.exclusive_stream->hold_preemption)
> >> +               eb->request->flags |= I915_REQUEST_FLAGS_PERF;
> > Just to reassure myself that this is the behaviour you:
> >
> > If the exclusive_stream is changed before the request is executed, it is
> > likely that we no longer notice the earlier preemption-protection. This
> > should not matter because the listener is no longer interested in those
> > events?
> > -Chris
> >
> 
> Yeah, dropping the perf stream before your queries complete and you're 
> in undefined behavior territory.

Then this should do what you want, and if I break it in future, I have
to fix it ;)

Hmm, this definitely merits some selftest/igt as I am very liable to
break it.

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris