[PATCH 5/8] active-ref

[Chris Wilson]

---
 drivers/gpu/drm/i915/i915_active.c | 57 ++++++++++++++++++++++++++----
 drivers/gpu/drm/i915/i915_active.h |  3 ++
 2 files changed, 53 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
index c4048628188a..3db88e3af0a1 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -217,11 +217,10 @@ excl_retire(struct dma_fence *fence, struct dma_fence_cb *cb)
 }
 
 static struct i915_active_fence *
-active_instance(struct i915_active *ref, struct intel_timeline *tl)
+active_instance(struct i915_active *ref, u64 idx)
 {
 	struct active_node *node, *prealloc;
 	struct rb_node **p, *parent;
-	u64 idx = tl->fence_context;
 
 	/*
 	 * We track the most recently used timeline to skip a rbtree search
@@ -367,7 +366,7 @@ int i915_active_ref(struct i915_active *ref,
 	if (err)
 		return err;
 
-	active = active_instance(ref, tl);
+	active = active_instance(ref, tl->fence_context);
 	if (!active) {
 		err = -ENOMEM;
 		goto out;
@@ -391,8 +390,10 @@ int i915_active_ref(struct i915_active *ref,
 	return err;
 }
 
-struct dma_fence *
-i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f)
+static struct dma_fence *
+__i915_active_set_fence(struct i915_active *ref,
+			struct i915_active_fence *active,
+			struct dma_fence *fence)
 {
 	struct dma_fence *prev;
 
@@ -400,16 +401,58 @@ i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f)
 	GEM_BUG_ON(i915_active_is_idle(ref));
 
 	rcu_read_lock();
-	prev = __i915_active_fence_set(&ref->excl, f);
+	prev = __i915_active_fence_set(active, fence);
 	if (prev)
 		prev = dma_fence_get_rcu(prev);
 	else
-		atomic_inc(&ref->count);
+		__i915_active_acquire(ref);
 	rcu_read_unlock();
 
 	return prev;
 }
 
+struct dma_fence *
+__i915_active_ref(struct i915_active *ref, u64 idx, struct dma_fence *fence)
+{
+	struct i915_active_fence *active;
+	struct dma_fence *prev;
+	int err;
+
+	/* Prevent reaping in case we malloc/wait while building the tree */
+	err = i915_active_acquire(ref);
+	if (err)
+		return ERR_PTR(err);
+
+	active = active_instance(ref, idx);
+	if (!active) {
+		i915_active_release(ref);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	if (is_barrier(active)) { /* proto-node used by our idle barrier */
+		/*
+		 * This request is on the kernel_context timeline, and so
+		 * we can use it to substitute for the pending idle-barrer
+		 * request that we want to emit on the kernel_context.
+		 */
+		__active_del_barrier(ref, node_from_active(active));
+		RCU_INIT_POINTER(active->fence, NULL);
+		atomic_dec(&ref->count);
+	}
+
+	prev = __i915_active_set_fence(ref, active, fence);
+
+	i915_active_release(ref);
+	return prev;
+}
+
+struct dma_fence *
+i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f)
+{
+	/* We expect the caller to manage the exclusive timeline ordering */
+	return __i915_active_set_fence(ref, &ref->excl, f);
+}
+
 bool i915_active_acquire_if_busy(struct i915_active *ref)
 {
 	debug_active_assert(ref);
diff --git a/drivers/gpu/drm/i915/i915_active.h b/drivers/gpu/drm/i915/i915_active.h
index b3282ae7913c..a5b1ce3d114f 100644
--- a/drivers/gpu/drm/i915/i915_active.h
+++ b/drivers/gpu/drm/i915/i915_active.h
@@ -163,6 +163,9 @@ void __i915_active_init(struct i915_active *ref,
 	__i915_active_init(ref, active, retire, &__mkey, &__wkey);	\
 } while (0)
 
+struct dma_fence *
+__i915_active_ref(struct i915_active *ref, u64 idx, struct dma_fence *fence);
+
 int i915_active_ref(struct i915_active *ref,
 		    struct intel_timeline *tl,
 		    struct dma_fence *fence);
-- 
2.20.1