[Intel-gfx] [PATCH] drm/i915: Always kick the execlists tasklet after reset

[Chris Wilson]

Quoting Mika Kuoppala (2019-03-15 10:39:25)
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > Quoting Mika Kuoppala (2019-03-15 10:10:20)
> >> Chris Wilson <chris at chris-wilson.co.uk> writes:
> >> > +static inline bool __tasklet_enable(struct tasklet_struct *t)
> >> > +{
> >> > +     return atomic_dec_and_test(&t->count);
> >> > +}
> >> > +
> >> >  #endif /* __I915_GEM_H__ */
> >> > diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> >> > index dc3de09c7586..b2d0e16645c7 100644
> >> > --- a/drivers/gpu/drm/i915/intel_lrc.c
> >> > +++ b/drivers/gpu/drm/i915/intel_lrc.c
> >> > @@ -2030,7 +2030,8 @@ static void execlists_reset_finish(struct intel_engine_cs *engine)
> >> >       if (!RB_EMPTY_ROOT(&execlists->queue.rb_root))
> >> >               execlists->tasklet.func(execlists->tasklet.data);
> >> >  
> >> > -     tasklet_enable(&execlists->tasklet);
> >> > +     if (__tasklet_enable(&execlists->tasklet))
> >> > +             tasklet_hi_schedule(&execlists->tasklet);
> >> 
> >> Why not just go fully unconditional, enable and schedule?
> >
> > If we schedule before we finish the reset, the tasklet busyspins, get's
> > kicked to ksoftirqd, which then busyspins for its timeslice and gets
> > bumped around by the scheduler until finally ready.
> 
> Hmm stealing the whole timeslice is rude. Just wanted
> to weight in the extra trickery. Random thought was
> to advocate for execlists_tasklet_enable|disable,
> but perhaps we are not there yet.

Keep sowing those seeds!

By the way, remind yourself on how our execlists submission works...
https://patchwork.freedesktop.org/patch/291941/?series=57942&rev=2
-Chris