[Intel-gfx] [PATCH] drm/i915: Remove incorrect warning in context cleanup

[Chris Wilson]

On Tue, Nov 24, 2015 at 01:17:57PM +0000, Tvrtko Ursulin wrote:
> 
> On 24/11/15 12:53, Chris Wilson wrote:
> >On Tue, Nov 24, 2015 at 11:58:22AM +0100, Daniel Vetter wrote:
> >>On Fri, Nov 20, 2015 at 01:23:36PM +0000, Tvrtko Ursulin wrote:
> >>>From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>>
> >>>Commit e9f24d5fb7cf3628b195b18ff3ac4e37937ceeae
> >>>Author: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>>Date:   Mon Oct 5 13:26:36 2015 +0100
> >>>
> >>>     drm/i915: Clean up associated VMAs on context destruction
> >>>
> >>>Added a warning based on an incorrect assumption that all VMAs
> >>>in a VM will be on the inactive list at the point last reference
> >>>to a context and VM is dropped.
> >>>
> >>>This is not true because i915_gem_object_retire__read will not
> >>>put VMA on the inactive list until all activities on the object
> >>>in question (in all VMs) have been retired.
> >>>
> >>>As a consequence, whether or not a context/VM will be destroyed
> >>>with its VMAs still on the active list, can depend on completely
> >>>unrelated activities using the same object from a different
> >>>context or engine.
> >>>
> >>>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>>Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92638
> >>>Testcase: igt/gem_request_retire/retire-vma-not-inactive
> >>>Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> >>>Cc: Chris Wilson <chris at chris-wilson.co.uk>
> >>>Cc: Michel Thierry <michel.thierry at intel.com>
> >>
> >>Queued for -next, thanks for the patch.
> >
> >The WARN_ON is accurate though. The original patch fails to fix even the
> >limited aspect of the bug it claimed to.
> 
> That is not true. It only makes it a bit more limited, and not by
> its fault even. Even with that it makes things a bit better, not
> worse.

It makes the code worse for very limited improvement, for which we did
not have a publically reported bug, i.e. the impact is very small.
 
> And does not impede your VMA rewrite at all. For which I did offer
> help to review as you send out in manageable chunks.

I have been.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre