Document PyThreadState_SetAsyncExc().
diff --git a/Doc/api/init.tex b/Doc/api/init.tex
index 388f479..44bfa3e 100644
--- a/Doc/api/init.tex
+++ b/Doc/api/init.tex
@@ -685,6 +685,20 @@
thread is active, and \NULL meant that an exception was raised]{2.3}
\end{cfuncdesc}
+\begin{cfuncdesc}{int}{PyThreadState_SetAsyncExc}{long id, PyObject *exc}
+ Asynchronously raise an exception in a thread.
+ The \var{id} argument is the thread id of the target thread;
+ \var{exc} is the exception object to be raised.
+ This function does not steal any references to \var{exc}.
+ To prevent naive misuse, you must write your own C extension
+ to call this. Must be called with the GIL held.
+ Returns the number of thread states modified; if it returns a number
+ greater than one, you're in trouble, and you should call it again
+ with \var{exc} set to \constant{NULL} to revert the effect.
+ This raises no exceptions.
+ \versionadded{2.3}
+\end{cfuncdesc}
+
\section{Profiling and Tracing \label{profiling}}