[PATCH 2/2] drm/i915: Remove completed fences after a wait

[Chris Wilson <chris@chris-wilson.co.uk>]

If we wait up on the full (i.e. all shared fences, or upon an exclusive fence)
reservation object successfully, we know that all fences beneath it have
been signaled, so long as no new fences were added whilst we slept. If the
reservation_object remains the same, as detected by its seqcount, we can
then reap all the fences upon completion.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index cf8132c49600..e55a60c1afce 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -424,7 +424,9 @@ i915_gem_object_wait_reservation(struct reservation_object *resv,
 				 long timeout,
 				 struct intel_rps_client *rps)
 {
+	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;
@@ -449,15 +451,26 @@ i915_gem_object_wait_reservation(struct reservation_object *resv,
 		for (; i < count; i++)
 			dma_fence_put(shared[i]);
 		kfree(shared);
+
+		prune_fences = timeout >= 0;
 	} else {
 		excl = reservation_object_get_excl_rcu(resv);
 	}
 
-	if (excl && timeout >= 0)
+	if (excl && timeout >= 0) {
 		timeout = i915_gem_object_wait_fence(excl, flags, timeout, rps);
+		prune_fences = timeout >= 0;
+	}
 
 	dma_fence_put(excl);
 
+	if (prune_fences && !__read_seqcount_retry(&resv->seq, seq)) {
+		reservation_object_lock(resv, NULL);
+		if (!__read_seqcount_retry(&resv->seq, seq))
+			reservation_object_add_excl_fence(resv, NULL);
+		reservation_object_unlock(resv);
+	}
+
 	return timeout;
 }
 
-- 
2.11.0

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx