[Intel-gfx] [PATCH] drm/i915: Skip an engine reset if it recovered before our preparations

[Chris Wilson]

Quoting Michel Thierry (2017-12-16 00:02:47)
> Hi,
> 
> On 12/15/2017 3:52 PM, Chris Wilson wrote:
> > At the beginning of a reset, we disable the submission method and find
> > the stuck request. We expect to find a stuck request for we have
> > declared the engine stalled. However, if we find no active request, the
> > engine must have recovered from its stall before we could issue a reset,
> > so let the engine continue on without a reset. If the engine is truly
> > stuck, we will back soon enough with the next reset attempt.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Michel Thierry <michel.thierry at intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> > ---
> >   drivers/gpu/drm/i915/i915_drv.c | 14 +++++++-------
> >   1 file changed, 7 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > index ca9f4b2862eb..6f24435ddffe 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -2011,19 +2011,19 @@ int i915_reset_engine(struct intel_engine_cs *engine, unsigned int flags)
> >   
> >       GEM_BUG_ON(!test_bit(I915_RESET_ENGINE + engine->id, &error->flags));
> >   
> > -     if (!(flags & I915_RESET_QUIET)) {
> > -             dev_notice(engine->i915->drm.dev,
> > -                        "Resetting %s after gpu hang\n", engine->name);
> > -     }
> > -     error->reset_engine_count[engine->id]++;
> > -
> >       active_request = i915_gem_reset_prepare_engine(engine);
> > -     if (IS_ERR(active_request)) {
> > +     if (IS_ERR_OR_NULL(active_request)) {
> >               DRM_DEBUG_DRIVER("Previous reset failed, promote to full reset\n");
> >               ret = PTR_ERR(active_request);
> 
> Will a static checker complain about PTR_ERR(NULL)?

It shouldn't. PTR_ERR(NULL) -> 0 is one of the valid tricks of PTR_ERR.

> And the DRM_DEBUG_DRIVER isn't also correct in that case.

Bah, I was betting on those who read this would know that the full chip
reset was pardoned. If you want, we can just remove the debug.
-Chris