@@ -564,7 +564,7 @@ Additionally, when extending or embedding Python, calling :c:func:`fork`
 directly rather than through :func:`os.fork` (and returning to or calling
 into Python) may result in a deadlock by one of Python's internal locks
 being held by a thread that is defunct after the fork.
-:c:func:`PyOS_AfterFork` tries to reset the necessary locks, but is not
+:c:func:`PyOS_AfterFork_Child` tries to reset the necessary locks, but is not
 always able to.
 
 
@@ -675,9 +675,9 @@ code, or when embedding the Python interpreter:
 
 .. c:function:: void PyEval_ReInitThreads()
 
-   This function is called from :c:func:`PyOS_AfterFork` to ensure that newly
-   created child processes don't hold locks referring to threads which
-   are not running in the child process.
+   This function is called from :c:func:`PyOS_AfterFork_Child` to ensure
+   that newly created child processes don't hold locks referring to threads
+   which are not running in the child process.
 
 
 The following functions use thread-local storage, and are not compatible
 
@@ -166,6 +166,10 @@ Serhiy Storchaka in :issue:`28682`.)
 Added support for :ref:`file descriptors <path_fd>` in :func:`~os.scandir`
 on Unix.  (Contributed by Serhiy Storchaka in :issue:`25996`.)
 
+New function :func:`os.register_at_fork` allows registering Python callbacks
+to be executed on a process fork.  (Contributed by Antoine Pitrou in
+:issue:`16500`.)
+
 unittest.mock
 -------------
 
@@ -243,6 +247,11 @@ Build and C API Changes
 * Added functions :c:func:`PySlice_Unpack` and :c:func:`PySlice_AdjustIndices`.
   (Contributed by Serhiy Storchaka in :issue:`27867`.)
 
+* :c:func:`PyOS_AfterFork` is deprecated in favour of the new functions
+  :c:func:`PyOS_BeforeFork`, :c:func:`PyOS_AfterFork_Parent` and
+  :c:func:`PyOS_AfterFork_Child`.  (Contributed by Antoine Pitrou in
+  :issue:`16500`.)
+
 
 Deprecated
 ==========
 
@@ -1320,8 +1320,8 @@ def main_thread():
 
 def _after_fork():
     # This function is called by Python/ceval.c:PyEval_ReInitThreads which
-    # is called from PyOS_AfterFork.  Here we cleanup threading module state
-    # that should not exist after a fork.
+    # is called from PyOS_AfterFork_Child.  Here we cleanup threading module
+    # state that should not exist after a fork.
 
     # Reset _active_limbo_lock, in case we forked while the lock was held
     # by another (non-forked) thread.  http://bugs.python.org/issue874900
 
@@ -1052,6 +1052,9 @@ Windows
 C API
 -----
 
+- bpo-16500: Deprecate PyOS_AfterFork() and add PyOS_BeforeFork(),
+  PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().
+
 - bpo-6532: The type of results of PyThread_start_new_thread() and
   PyThread_get_thread_ident(), and the id parameter of
   PyThreadState_SetAsyncExc() changed from "long" to "unsigned long".
 
@@ -232,10 +232,10 @@ PyEval_ReleaseThread(PyThreadState *tstate)
     drop_gil(tstate);
 }
 
-/* This function is called from PyOS_AfterFork to destroy all threads which are
- * not running in the child process, and clear internal locks which might be
- * held by those threads. (This could also be done using pthread_atfork
- * mechanism, at least for the pthreads implementation.) */
+/* This function is called from PyOS_AfterFork_Child to destroy all threads
+ * which are not running in the child process, and clear internal locks
+ * which might be held by those threads.
+ */
 
 void
 PyEval_ReInitThreads(void)
 
@@ -194,7 +194,7 @@ _PyImport_ReleaseLock(void)
     return 1;
 }
 
-/* This function is called from PyOS_AfterFork to ensure that newly
+/* This function is called from PyOS_AfterFork_Child to ensure that newly
    created child processes do not share locks with the parent.
    We now acquire the import lock around fork() calls but on some platforms
    (Solaris 9 and earlier? see isue7242) that still left us with problems. */
 
@@ -800,7 +800,7 @@ _PyGILState_Fini(void)
     autoInterpreterState = NULL;
 }
 
-/* Reset the TLS key - called by PyOS_AfterFork().
+/* Reset the TLS key - called by PyOS_AfterFork_Child().
  * This should not be necessary, but some - buggy - pthread implementations
  * don't reset TLS upon fork(), see issue #10517.
  */
 
@@ -325,7 +325,7 @@ PyThread_delete_key_value(int key)
 }
 
 /* Forget everything not associated with the current thread id.
- * This function is called from PyOS_AfterFork().  It is necessary
+ * This function is called from PyOS_AfterFork_Child().  It is necessary
  * because other thread ids which were in use at the time of the fork
  * may be reused for new threads created in the forked process.
  */
Original file line number	Diff line number	Diff line change
@@ -194,7 +194,7 @@ _PyImport_ReleaseLock(void)
194	194	return 1;
195	195	}
196	196
197		- /* This function is called from PyOS_AfterFork to ensure that newly
	197	+ /* This function is called from PyOS_AfterFork_Child to ensure that newly
198	198	created child processes do not share locks with the parent.
199	199	We now acquire the import lock around fork() calls but on some platforms
200	200	(Solaris 9 and earlier? see isue7242) that still left us with problems. */
Original file line number	Diff line number	Diff line change
@@ -800,7 +800,7 @@ _PyGILState_Fini(void)
800	800	autoInterpreterState = NULL;
801	801	}
802	802
803		- /* Reset the TLS key - called by PyOS_AfterFork().
	803	+ /* Reset the TLS key - called by PyOS_AfterFork_Child().
804	804	* This should not be necessary, but some - buggy - pthread implementations
805	805	* don't reset TLS upon fork(), see issue #10517.
806	806	*/
Original file line number	Diff line number	Diff line change
@@ -325,7 +325,7 @@ PyThread_delete_key_value(int key)
325	325	}
326	326
327	327	/* Forget everything not associated with the current thread id.
328		- * This function is called from PyOS_AfterFork(). It is necessary
	328	+ * This function is called from PyOS_AfterFork_Child(). It is necessary
329	329	* because other thread ids which were in use at the time of the fork
330	330	* may be reused for new threads created in the forked process.
331	331	*/