Merged revisions 73694,73708,73738 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
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r73694 | jesse.noller | 2009-06-29 14:24:26 -0400 (Mon, 29 Jun 2009) | 1 line
Issue 5740: multiprocessing.connection.* authkey fixes
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r73708 | jesse.noller | 2009-06-30 13:11:52 -0400 (Tue, 30 Jun 2009) | 1 line
Resolves issues 5155, 5313, 5331 - bad file descriptor error with processes in processes
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r73738 | r.david.murray | 2009-06-30 22:49:10 -0400 (Tue, 30 Jun 2009) | 2 lines
Make punctuation prettier and break up run-on sentence.
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diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index d1a0334..af7af2b 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -1715,7 +1715,7 @@
generally be omitted since it can usually be inferred from the format of
*address*. (See :ref:`multiprocessing-address-formats`)
- If *authentication* is ``True`` or *authkey* is a string then digest
+ If *authenticate* is ``True`` or *authkey* is a string then digest
authentication is used. The key used for authentication will be either
*authkey* or ``current_process().authkey)`` if *authkey* is ``None``.
If authentication fails then :exc:`AuthenticationError` is raised. See
@@ -1757,7 +1757,7 @@
If *authkey* is ``None`` and *authenticate* is ``True`` then
``current_process().authkey`` is used as the authentication key. If
- *authkey* is ``None`` and *authentication* is ``False`` then no
+ *authkey* is ``None`` and *authenticate* is ``False`` then no
authentication is done. If authentication fails then
:exc:`AuthenticationError` is raised. See :ref:`multiprocessing-auth-keys`.
@@ -2099,6 +2099,38 @@
for i in range(10):
Process(target=f, args=(lock,)).start()
+Beware replacing sys.stdin with a "file like object"
+
+ :mod:`multiprocessing` originally unconditionally called::
+
+ os.close(sys.stdin.fileno())
+
+ in the :meth:`multiprocessing.Process._bootstrap` method --- this resulted
+ in issues with processes-in-processes. This has been changed to::
+
+ sys.stdin.close()
+ sys.stdin = open(os.devnull)
+
+ Which solves the fundamental issue of processes colliding with each other
+ resulting in a bad file descriptor error, but introduces a potential danger
+ to applications which replace :func:`sys.stdin` with a "file-like object"
+ with output buffering. This danger is that if multiple processes call
+ :func:`close()` on this file-like object, it could result in the same
+ data being flushed to the object multiple times, resulting in corruption.
+
+ If you write a file-like object and implement your own caching, you can
+ make it fork-safe by storing the pid whenever you append to the cache,
+ and discarding the cache when the pid changes. For example::
+
+ @property
+ def cache(self):
+ pid = os.getpid()
+ if pid != self._pid:
+ self._pid = pid
+ self._cache = []
+ return self._cache
+
+ For more information, see :issue:`5155`, :issue:`5313` and :issue:`5331`
Windows
~~~~~~~