[PATCH v5 10/13] drm/i915: try to simplify make_{un}shrinkable

[Thomas Hellström]

On Mon, 2021-09-27 at 12:41 +0100, Matthew Auld wrote:
> Drop the atomic shrink_pin stuff, and just have make_{un}shrinkable
> update the shrinker visible lists immediately. This at least
> simplifies
> the next patch, and does make the behaviour more obvious. The
> potential
> downside is that make_unshrinkable now grabs a global lock even when
> the
> object itself is no longer shrinkable(transitioning from purgeable <-
> >
> shrinkable doesn't seem to be a thing), for example in the ppGTT
> insertion paths we should now be careful not to needlessly call
> make_unshrinkable multiple times. Outside of that there is some
> fallout
> in intel_context which relies on nesting calls to shrink_pin.
> 
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>

Hmm. One thing that worries me a bit here: Let's say we have, for
example an LMEM context state, and TTM has it made unshrinkable. Then
the context becomes active and calls _make_unshrinkable again. And when
it retires it callse _make_shrinkable. Doesn't it end up on the
shrinker list at that point, even if still in LMEM?

/Thomas