[PATCH 1/5] drm/i915: stop pruning reservation object after wait

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

The reservation object should be capable of handling its internal memory
management itself. And since we search for a free slot to add the fence
from the beginning this is actually a waste of time and only minimal helpful.

Drop it to allow removal of the seqno handling in the reservation object.

This essentially reverts commit "drm/i915: Remove completed fences after a wait".

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_wait.c | 27 ------------------------
 1 file changed, 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_wait.c b/drivers/gpu/drm/i915/gem/i915_gem_wait.c
index 26ec6579b7cd..bb64ec6bef8e 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_wait.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_wait.c
@@ -35,9 +35,7 @@ i915_gem_object_wait_reservation(struct reservation_object *resv,
 				 unsigned int flags,
 				 long timeout)
 {
-	unsigned int seq = __read_seqcount_begin(&resv->seq);
 	struct dma_fence *excl;
-	bool prune_fences = false;
 
 	if (flags & I915_WAIT_ALL) {
 		struct dma_fence **shared;
@@ -61,17 +59,6 @@ i915_gem_object_wait_reservation(struct reservation_object *resv,
 		for (; i < count; i++)
 			dma_fence_put(shared[i]);
 		kfree(shared);
-
-		/*
-		 * If both shared fences and an exclusive fence exist,
-		 * then by construction the shared fences must be later
-		 * than the exclusive fence. If we successfully wait for
-		 * all the shared fences, we know that the exclusive fence
-		 * must all be signaled. If all the shared fences are
-		 * signaled, we can prune the array and recover the
-		 * floating references on the fences/requests.
-		 */
-		prune_fences = count && timeout >= 0;
 	} else {
 		excl = reservation_object_get_excl_rcu(resv);
 	}
@@ -80,20 +67,6 @@ i915_gem_object_wait_reservation(struct reservation_object *resv,
 		timeout = i915_gem_object_wait_fence(excl, flags, timeout);
 
 	dma_fence_put(excl);
-
-	/*
-	 * Opportunistically prune the fences iff we know they have *all* been
-	 * signaled and that the reservation object has not been changed (i.e.
-	 * no new fences have been added).
-	 */
-	if (prune_fences && !__read_seqcount_retry(&resv->seq, seq)) {
-		if (reservation_object_trylock(resv)) {
-			if (!__read_seqcount_retry(&resv->seq, seq))
-				reservation_object_add_excl_fence(resv, NULL);
-			reservation_object_unlock(resv);
-		}
-	}
-
 	return timeout;
 }
 
-- 
2.17.1