[Intel-gfx] [PATCH] drm/i915: Prune the reservation shared fence array

[Chris Wilson]

The shared fence array is not autopruning and may continue to grow as an
object is shared between new timelines. Take the opportunity when we
think the object is idle (we have to confirm that any external fence is
also signaled) to decouple all the fences.

Fixes: d07f0e59b2c7 ("drm/i915: Move GEM activity tracking into a common struct reservation_object")
Fixes: 80b204bce8f2 ("drm/i915: Enable multiple timelines")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_vma.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 6d456582edf4..44585300fdff 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -53,6 +53,12 @@ i915_vma_retire(struct i915_gem_active *active,
 	if (--obj->active_count)
 		return;
 
+	/* Prune the shared fence arrays iff completely idle (inc. external) */
+	ww_mutex_lock(&obj->resv->lock, NULL);
+	if (reservation_object_test_signaled_rcu(obj->resv, true))
+		reservation_object_add_excl_fence(obj->resv, NULL);
+	ww_mutex_unlock(&obj->resv->lock);
+
 	/* Bump our place on the bound list to keep it roughly in LRU order
 	 * so that we don't steal from recently used but inactive objects
 	 * (unless we are forced to ofc!)
-- 
2.10.2