issue3770: if SEM_OPEN is 0, disable the mp.synchronize module, rev. Nick Coghlan, Damien Miller
diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index 42d76a3..a005dc4 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -18,6 +18,13 @@
leverage multiple processors on a given machine. It runs on both Unix and
Windows.
+.. warning::
+
+ This package largely requires a functioning shared semaphore
+ implementation on the host operating system to function. Without one, the
+ :mod:`multiprocessing.synchronize` module will be disabled, and attempts to
+ import it will result in an ImportError. See
+ http://bugs.python.org/issue3770 for additional information.
The :class:`Process` class
~~~~~~~~~~~~~~~~~~~~~~~~~~