[3.14] gh-91555: add warning to docs about possibility of deadlock/infinite recursion...

(cherry picked from commit a4625d597f9fc2d083fbb9c22d3ffcec73b2061a)

diff --git a/Doc/library/logging.handlers.rst b/Doc/library/logging.handlers.rst
index 8f3aa1dfdd0cde5e11343db6a39d87000a401326..d74ef73ee284979b7c8ae8565780e7d655899731 100644 (file)
--- a/Doc/library/logging.handlers.rst
+++ b/Doc/library/logging.handlers.rst
@@ -1059,6 +1059,15 @@ possible, while any potentially slow operations (such as sending an email via
    .. note:: If you are using :mod:`multiprocessing`, you should avoid using
       :class:`~queue.SimpleQueue` and instead use :class:`multiprocessing.Queue`.
 
+   .. warning::
+
+      The :mod:`multiprocessing` module uses an internal logger created and
+      accessed via :meth:`~multiprocessing.get_logger`.
+      :class:`multiprocessing.Queue` will log ``DEBUG`` level messages upon
+      items being queued. If those log messages are processed by a
+      :class:`QueueHandler` using the same :class:`multiprocessing.Queue` instance,
+      it will cause a deadlock or infinite recursion.
+
    .. method:: emit(record)
 
       Enqueues the result of preparing the LogRecord. Should an exception