[PATCH] drm/i915/ttm: Fix illegal addition to shrinker list

[Matthew Auld]

On 10/11/2021 08:55, Thomas Hellström wrote:
> There's a small window of opportunity during which the adjust_lru()
> function can be called with a GEM refcount of zero from the TTM
> eviction code. This results in a kernel BUG().
> 
> Ensure that we don't attempt to modify the GEM shrinker lists unless
> we have a GEM refcount.
> 
> Fixes: ebd4a8ec7799 ("drm/i915/ttm: move shrinker management into adjust_lru")
> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld at intel.com>