drm/amdgpu: add amdgpu_sync_clone

Cloning a sync object is useful for waiting for a sync object
without locking the original structure indefinitely, blocking
other threads.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c

@@ -322,6 +322,41 @@ struct dma_fence *amdgpu_sync_get_fence(struct amdgpu_sync *sync, bool *explicit
 	return NULL;
 }
 
+/**
+ * amdgpu_sync_clone - clone a sync object
+ *
+ * @source: sync object to clone
+ * @clone: pointer to destination sync object
+ *
+ * Adds references to all unsignaled fences in @source to @clone. Also
+ * removes signaled fences from @source while at it.
+ */
+int amdgpu_sync_clone(struct amdgpu_sync *source, struct amdgpu_sync *clone)
+{
+	struct amdgpu_sync_entry *e;
+	struct hlist_node *tmp;
+	struct dma_fence *f;
+	int i, r;
+
+	hash_for_each_safe(source->fences, i, tmp, e, node) {
+		f = e->fence;
+		if (!dma_fence_is_signaled(f)) {
+			r = amdgpu_sync_fence(NULL, clone, f, e->explicit);
+			if (r)
+				return r;
+		} else {
+			hash_del(&e->node);
+			dma_fence_put(f);
+			kmem_cache_free(amdgpu_sync_slab, e);
+		}
+	}
+
+	dma_fence_put(clone->last_vm_update);
+	clone->last_vm_update = dma_fence_get(source->last_vm_update);
+
+	return 0;
+}
+
 int amdgpu_sync_wait(struct amdgpu_sync *sync, bool intr)
 {
 	struct amdgpu_sync_entry *e;

drivers/gpu/drm/amd/amdgpu/amdgpu_sync.h

@@ -50,6 +50,7 @@ int amdgpu_sync_resv(struct amdgpu_device *adev,
 struct dma_fence *amdgpu_sync_peek_fence(struct amdgpu_sync *sync,
 				     struct amdgpu_ring *ring);
 struct dma_fence *amdgpu_sync_get_fence(struct amdgpu_sync *sync, bool *explicit);
+int amdgpu_sync_clone(struct amdgpu_sync *source, struct amdgpu_sync *clone);
 int amdgpu_sync_wait(struct amdgpu_sync *sync, bool intr);
 void amdgpu_sync_free(struct amdgpu_sync *sync);
 int amdgpu_sync_init(void);