Extracted conversion function caching into tensor_conversion_registry

This change also fixes a race condition in the cache population logic
which could result in cache being populated more than once for a particular
type.

PiperOrigin-RevId: 255590346

tensorflow/python/framework/ops.py

@@ -81,12 +81,6 @@ _api_usage_gauge = monitoring.BoolGauge(
 
 # pylint: disable=protected-access
 _TensorLike = tensor_like._TensorLike
-_tensor_conversion_func_registry = \
-    tensor_conversion_registry._tensor_conversion_func_registry
-_tensor_conversion_func_cache = \
-    tensor_conversion_registry._tensor_conversion_func_cache
-_tensor_conversion_func_lock = \
-    tensor_conversion_registry._tensor_conversion_func_lock
 # pylint: enable=protected-access
 
 
@@ -1180,19 +1174,7 @@ def internal_convert_to_tensor(value,
           (dtype.name, value.dtype.name, value))
     return value
 
-  unwrapped_type = type(value)
-  conversion_func_list = _tensor_conversion_func_cache.get(unwrapped_type, None)
-  if conversion_func_list is None:
-    with _tensor_conversion_func_lock:
-      conversion_func_list = []
-      for _, funcs_at_priority in sorted(
-          _tensor_conversion_func_registry.items()):
-        for base_type, conversion_func in funcs_at_priority:
-          if isinstance(value, base_type):
-            conversion_func_list.append((base_type, conversion_func))
-      _tensor_conversion_func_cache[unwrapped_type] = conversion_func_list
-
-  for base_type, conversion_func in conversion_func_list:
+  for base_type, conversion_func in tensor_conversion_registry.get(type(value)):
     # If dtype is None but preferred_dtype is not None, we try to
     # cast to preferred_dtype first.
     ret = None

tensorflow/python/framework/tensor_conversion_registry.py

@@ -108,3 +108,29 @@ def register_tensor_conversion_function(base_type,
       _tensor_conversion_func_registry[priority] = funcs_at_priority
     funcs_at_priority.append((base_type, conversion_func))
     _tensor_conversion_func_cache = {}
+
+
+def get(query):
+  """Get conversion function for objects of `cls`.
+
+  Args:
+    query: The type to query for.
+
+  Returns:
+    A list of conversion functions in increasing order of priority.
+  """
+  conversion_funcs = _tensor_conversion_func_cache.get(query)
+  if conversion_funcs is None:
+    with _tensor_conversion_func_lock:
+      # Has another thread populated the cache in the meantime?
+      conversion_funcs = _tensor_conversion_func_cache.get(query)
+      if conversion_funcs is None:
+        conversion_funcs = []
+        for _, funcs_at_priority in sorted(
+            _tensor_conversion_func_registry.items()):
+          conversion_funcs.extend(
+              (base_type, conversion_func)
+              for base_type, conversion_func in funcs_at_priority
+              if issubclass(query, base_type))
+        _tensor_conversion_func_cache[query] = conversion_funcs
+  return conversion_funcs