[Python-checkins] cpython (merge 3.3 -> default): Merge.
richard.oudkerk
python-checkins at python.org
Sun Nov 17 18:04:49 CET 2013
http://hg.python.org/cpython/rev/8a8556947dd0
changeset: 87207:8a8556947dd0
parent: 87203:18d95780100e
parent: 87206:11cafbe6519f
user: Richard Oudkerk <shibturn at gmail.com>
date: Sun Nov 17 17:03:19 2013 +0000
summary:
Merge.
files:
Doc/library/multiprocessing.rst | 24 +++++++++++++++-----
1 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -1172,12 +1172,24 @@
ctypes type or a one character typecode of the kind used by the :mod:`array`
module. *\*args* is passed on to the constructor for the type.
- If *lock* is ``True`` (the default) then a new lock object is created to
- synchronize access to the value. If *lock* is a :class:`Lock` or
- :class:`RLock` object then that will be used to synchronize access to the
- value. If *lock* is ``False`` then access to the returned object will not be
- automatically protected by a lock, so it will not necessarily be
- "process-safe".
+ If *lock* is ``True`` (the default) then a new recursive lock
+ object is created to synchronize access to the value. If *lock* is
+ a :class:`Lock` or :class:`RLock` object then that will be used to
+ synchronize access to the value. If *lock* is ``False`` then
+ access to the returned object will not be automatically protected
+ by a lock, so it will not necessarily be "process-safe".
+
+ Operations like ``+=`` which involve a read and write are not
+ atomic. So if, for instance, you want to atomically increment a
+ shared value it is insufficient to just do ::
+
+ counter.value += 1
+
+ Assuming the associated lock is recursive (which it is by default)
+ you can instead do ::
+
+ with counter.get_lock():
+ counter.value += 1
Note that *lock* is a keyword-only argument.
--
Repository URL: http://hg.python.org/cpython
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