drm/ttm: Add a ttm_ref_object_exists function
A function to be used to check whether a caller has put a ref object
(opened) a struct ttm_base_object
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
diff --git a/drivers/gpu/drm/ttm/ttm_object.c b/drivers/gpu/drm/ttm/ttm_object.c
index 53b51c4..d2a0533 100644
--- a/drivers/gpu/drm/ttm/ttm_object.c
+++ b/drivers/gpu/drm/ttm/ttm_object.c
@@ -270,6 +270,52 @@
}
EXPORT_SYMBOL(ttm_base_object_lookup_for_ref);
+/**
+ * ttm_ref_object_exists - Check whether a caller has a valid ref object
+ * (has opened) a base object.
+ *
+ * @tfile: Pointer to a struct ttm_object_file identifying the caller.
+ * @base: Pointer to a struct base object.
+ *
+ * Checks wether the caller identified by @tfile has put a valid USAGE
+ * reference object on the base object identified by @base.
+ */
+bool ttm_ref_object_exists(struct ttm_object_file *tfile,
+ struct ttm_base_object *base)
+{
+ struct drm_open_hash *ht = &tfile->ref_hash[TTM_REF_USAGE];
+ struct drm_hash_item *hash;
+ struct ttm_ref_object *ref;
+
+ rcu_read_lock();
+ if (unlikely(drm_ht_find_item_rcu(ht, base->hash.key, &hash) != 0))
+ goto out_false;
+
+ /*
+ * Verify that the ref object is really pointing to our base object.
+ * Our base object could actually be dead, and the ref object pointing
+ * to another base object with the same handle.
+ */
+ ref = drm_hash_entry(hash, struct ttm_ref_object, hash);
+ if (unlikely(base != ref->obj))
+ goto out_false;
+
+ /*
+ * Verify that the ref->obj pointer was actually valid!
+ */
+ rmb();
+ if (unlikely(atomic_read(&ref->kref.refcount) == 0))
+ goto out_false;
+
+ rcu_read_unlock();
+ return true;
+
+ out_false:
+ rcu_read_unlock();
+ return false;
+}
+EXPORT_SYMBOL(ttm_ref_object_exists);
+
int ttm_ref_object_add(struct ttm_object_file *tfile,
struct ttm_base_object *base,
enum ttm_ref_type ref_type, bool *existed)