diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1751,6 +1751,11 @@
     with equivalent code based on the semantics of the built-in function, unless
     the call site uses the ``builtin`` attribute. This is valid at call sites
     and on function declarations and definitions.
+``nocallback``
+    This attribute indicates that the function is not allowed to jump back into
+    the caller's translation unit, whether through invoking a callback function,
+    a direct, possibly transitive, external function call, use of ``longjmp``,
+    or other means.
 ``noduplicate``
     This attribute indicates that calls to the function cannot be
     duplicated. A call to a ``noduplicate`` function may be moved