Re: [PATCH 03/14] drm/i915/execlists: Flush the tasklet on parking

Chris Wilson
2019-05-02T13:53:57Z

Quoting Tvrtko Ursulin (2019-05-02 14:48:18)
>
> On 01/05/2019 12:45, Chris Wilson wrote:
> > Tidy up the cleanup sequence by always ensure that the tasklet is
> > flushed on parking (before we cleanup). The parking provides a
> > convenient point to ensure that the backend is truly idle.
> >
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > ---
> > drivers/gpu/drm/i915/gt/intel_lrc.c | 7 ++++++-
> > drivers/gpu/drm/i915/intel_guc_submission.c | 1 +
> > 2 files changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > index 851e62ddcb87..7be54b868d8e 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > @@ -2331,6 +2331,11 @@ static int gen8_init_rcs_context(struct i915_request *rq)
> > return i915_gem_render_state_emit(rq);
> > }
> >
> > +static void execlists_park(struct intel_engine_cs *engine)
> > +{
> > + tasklet_kill(&engine->execlists.tasklet);
>
> Isn't it actually a problem if tasklet is scheduled and unstarted, or
> even in progress at the point of engine getting parked?

That would be a broken driver. :|

We must be quite sure that engine isn't going to send an interrupt as we
are just about to drop the wakeref we need to service that interrupt.

tasklet_kill()
GEM_BUG_ON(engine->execlists.active);
-Chris