[Intel-gfx] [PATCH 2/2] drm/i915: Don't dereference request if it may have been retired

[Chris Wilson]

Quoting Chris Wilson (2019-06-18 17:19:51)
> This has count me out on countless occasions, when we retrieve a pointer
> from the submission/execlists backend, it does not carry a reference to
> the context or ring. Those are only pinned while the rquest is active,
> so if we see the request is completed, it may be in the process of being
> retired and those pointers defunct.
> 

I guess
Fixes: 3a068721a973 ("drm/i915: Show ring->start for the ELSP context/request queue")
v4.18!

> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110938
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris