[Intel-gfx] [PATCH v6 05/20] drm/i915/tdr: Add support for per engine reset recovery

[Chris Wilson]

On Wed, Apr 19, 2017 at 11:49:26AM +0100, Chris Wilson wrote:
> On Tue, Apr 18, 2017 at 01:23:20PM -0700, Michel Thierry wrote:
> > +	ret = i915_gem_reset_prepare_engine(engine);
> > +	if (ret) {
> > +		DRM_ERROR("Previous reset failed - promote to full reset\n");
> > +		goto error;
> > +	}
> > +
> > +	/*
> > +	 * the request that caused the hang is stuck on elsp, identify the
> > +	 * active request and drop it, adjust head to skip the offending
> > +	 * request to resume executing remaining requests in the queue.
> > +	 */
> 
> Hmm. Interesting. This relies on i915_gem_retire_requests() (i.e.
> struct_mutex) to skip replaying innocent requests, but here we should be
> asserting that we do have the hung request.
> 
> i.e.
> request = i915_gem_find_active_request(engine);
> if (!request)
> 	goto skip.

Forgot to mention this should include a "pardoned" check, i.e. that the
active request still matches the watchdog seqno.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre