Revision: 8341
http://matplotlib.svn.sourceforge.net/matplotlib/?rev=8341&view=rev
Author: mdboom
Date: 2010-05-28 17:42:05 +0000 (Fri, 28 May 2010)
Log Message:
-----------
Fix memory leak caused by never disconnecting callbacks.
Modified Paths:
--------------
trunk/matplotlib/lib/matplotlib/cbook.py
Modified: trunk/matplotlib/lib/matplotlib/cbook.py
===================================================================
--- trunk/matplotlib/lib/matplotlib/cbook.py 2010-05-28 16:56:45 UTC (rev
8340)
+++ trunk/matplotlib/lib/matplotlib/cbook.py 2010-05-28 17:42:05 UTC (rev
8341)
@@ -13,6 +13,7 @@
import os.path
import random
import urllib2
+import new
import matplotlib
@@ -124,12 +125,87 @@
callbacks.disconnect(ideat) # disconnect oneat
callbacks.process('eat', 456) # nothing will be called
+ In practice, one should always disconnect all callbacks when they
+ are no longer needed to avoid dangling references (and thus memory
+ leaks). However, real code in matplotlib rarely does so, and due
+ to its design, it is rather difficult to place this kind of code.
+ To get around this, and prevent this class of memory leaks, we
+ instead store weak references to bound methods only, so when the
+ destination object needs to die, the CallbackRegistry won't keep
+ it alive. The Python stdlib weakref module can not create weak
+ references to bound methods directly, so we need to create a proxy
+ object to handle weak references to bound methods (or regular free
+ functions). This technique was shared by Peter Parente on his
+ `"Mindtrove" blog
+ <http://mindtrove.info/articles/python-weak-references/>`_.
"""
+ class BoundMethodProxy(object):
+ '''
+ Our own proxy object which enables weak references to bound and unbound
+ methods and arbitrary callables. Pulls information about the function,
+ class, and instance out of a bound method. Stores a weak reference to
the
+ instance to support garbage collection.
+
+ @organization: IBM Corporation
+ @copyright: Copyright (c) 2005, 2006 IBM Corporation
+ @license: The BSD License
+
+ Minor bugfixes by Michael Droettboom
+ '''
+ def __init__(self, cb):
+ try:
+ try:
+ self.inst = ref(cb.im_self)
+ except TypeError:
+ self.inst = None
+ self.func = cb.im_func
+ self.klass = cb.im_class
+ except AttributeError:
+ self.inst = None
+ self.func = cb
+ self.klass = None
+
+ def __call__(self, *args, **kwargs):
+ '''
+ Proxy for a call to the weak referenced object. Take
+ arbitrary params to pass to the callable.
+
+ Raises `ReferenceError`: When the weak reference refers to
+ a dead object
+ '''
+ if self.inst is not None and self.inst() is None:
+ raise ReferenceError
+ elif self.inst is not None:
+ # build a new instance method with a strong reference to the
instance
+ mtd = new.instancemethod(self.func, self.inst(), self.klass)
+ else:
+ # not a bound method, just return the func
+ mtd = self.func
+ # invoke the callable and return the result
+ return mtd(*args, **kwargs)
+
+ def __eq__(self, other):
+ '''
+ Compare the held function and instance with that held by
+ another proxy.
+ '''
+ try:
+ if self.inst is None:
+ return self.func == other.func and other.inst is None
+ else:
+ return self.func == other.func and self.inst() ==
other.inst()
+ except Exception:
+ return False
+
+ def __ne__(self, other):
+ '''
+ Inverse of __eq__.
+ '''
+ return not self.__eq__(other)
+
def __init__(self, signals):
'*signals* is a sequence of valid signals'
self.signals = set(signals)
- # callbacks is a dict mapping the signal to a dictionary
- # mapping callback id to the callback function
self.callbacks = dict([(s, dict()) for s in signals])
self._cid = 0
@@ -146,8 +222,15 @@
func will be called
"""
self._check_signal(s)
- self._cid +=1
- self.callbacks[s][self._cid] = func
+ proxy = self.BoundMethodProxy(func)
+ for cid, callback in self.callbacks[s].items():
+ # Clean out dead references
+ if callback.inst is not None and callback.inst() is None:
+ del self.callbacks[s][cid]
+ elif callback == proxy:
+ return cid
+ self._cid += 1
+ self.callbacks[s][self._cid] = proxy
return self._cid
def disconnect(self, cid):
@@ -155,9 +238,12 @@
disconnect the callback registered with callback id *cid*
"""
for eventname, callbackd in self.callbacks.items():
- try: del callbackd[cid]
- except KeyError: continue
- else: return
+ try:
+ del callbackd[cid]
+ except KeyError:
+ continue
+ else:
+ return
def process(self, s, *args, **kwargs):
"""
@@ -165,8 +251,12 @@
callbacks on *s* will be called with *\*args* and *\*\*kwargs*
"""
self._check_signal(s)
- for func in self.callbacks[s].values():
- func(*args, **kwargs)
+ for cid, proxy in self.callbacks[s].items():
+ # Clean out dead references
+ if proxy.inst is not None and proxy.inst() is None:
+ del self.callbacks[s][cid]
+ else:
+ proxy(*args, **kwargs)
class Scheduler(threading.Thread):
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