Changes between Version 14 and Version 15 of DjangoSpecifications/Core/Threading

Timestamp:

Apr 14, 2008, 2:27:47 AM (17 years ago)

Author:

mrts

Comment:

--

DjangoSpecifications/Core/Threading

@@ -21 +21 @@
  1. global mutable data structures (lists and dictionaries, also instances) that are assigned to at module level but whose elements are modified in functions and that are accessed without using the `global` keyword (NOT THREAD-SAFE unless never modified).
 
+"Not thread-safe" has two broad subcategories:
+ * inefficiencies due to calls meant to occur only once occurring more than once (the general `if not foo: initialize foo`, including `memoize` decorator),
+ * errors due to incomplete initialization.
+
+Incomplete initialization errors can generally be avoided by using full
+assignment instead of elementwise modification (that's how it is done in the
+source mostly). That is,
+
+'''BAD'''
+{{{
+foo = []
+def bar():
+   ...
+   if not foo:
+      for x in y:
+         foo.append(x)
+}}}
+
+'''BETTER'''
+{{{
+foo = []
+def bar():
+   ...
+   global foo
+   if not foo:
+      tmp = []
+      for x in y:
+         tmp.append(x)
+      foo = tmp # atomic assignment
+}}}
+
 The following modules' use of globals needs review.
 
@@ -28 +59 @@
 ||settings and global_settings||?||not reviewed||
 ||utils/_decimal.py||lots, including code||not reviewed||
-
-'''THE FOLLOWING IS WORK IN PROGRESS.'''
-
-=== Settings ===
-
-FIXME: not reviewed. Replacing the `global_settings` with `settings` -- probably no major issues.
-
-=== utils/_decimal.py ===
-
-FIXME: not reviewed. Lot's of globals, global code as well.
+||django/contrib/sites/models.py||SITE_CACHE||minor, one db hit intended, more than one possible||
 
 === django/contrib/sites/models.py ===