Re: [PATCH 5/9] drm/i915/guc: Flush the work queue for GuC generated G2H

[Matthew Brost <matthew.brost@intel.com>]

On Thu, Aug 12, 2021 at 04:11:28PM +0200, Daniel Vetter wrote:
> On Wed, Aug 11, 2021 at 01:16:18AM +0000, Matthew Brost wrote:
> > Flush the work queue for GuC generated G2H messages durinr a GT reset.
> > This is accomplished by spinning on the the list of outstanding G2H to
> > go empty.
> > 
> > Fixes: eb5e7da736f3 ("drm/i915/guc: Reset implementation for new GuC interface")
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > Cc: <stable@vger.kernel.org>
> > ---
> >  drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > index 3cd2da6f5c03..e5eb2df11b4a 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -727,6 +727,11 @@ void intel_guc_submission_reset_prepare(struct intel_guc *guc)
> >  			wait_for_reset(guc, &guc->outstanding_submission_g2h);
> >  		} while (!list_empty(&guc->ct.requests.incoming));
> >  	}
> > +
> > +	/* Flush any GuC generated G2H */
> > +	while (!list_empty(&guc->ct.requests.incoming))
> > +		msleep(20);
> 
> flush_work or flush_workqueue, beacuse that comes with lockdep
> annotations. Dont hand-roll stuff like this if at all possible.

lockdep puked when used that.

Matt

> -Daniel
> 
> > +
> >  	scrub_guc_desc_for_outstanding_g2h(guc);
> >  }
> >  
> > -- 
> > 2.32.0
> > 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch