Changes between Version 22 and Version 23 of DjangoSpecifications/Core/Threading

Timestamp:

Apr 15, 2008, 9:49:11 AM (17 years ago)

Author:

mrts

Comment:

--

DjangoSpecifications/Core/Threading

@@ -25 +25 @@
  * errors due to incomplete initialization.
 
-When evaluating the inefficiencies, their impact should be considered in terms of their probability and the overhead of duplicated call. The worst case,
-{{{
-1. thread 1: if not foo: needs initializing
-2. thread 2: if not foo: needs initializing
+=== Inefficiencies ===
+
+When evaluating the inefficiencies, their impact should be considered in terms of their probability and overhead of the duplicated call. The duplicated case,
+{{{
+1. thread 1: if not foo: true, needs initializing
+2. thread 2: if not foo: true, needs initializing
 3. thread 1: initialize foo
 4. thread 2: initialize foo
 }}}
-is not that common and there are no large initialization overhead cases below, so the "inefficiency issues" are really non-issues. There is at least one bug though.
-
-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):
+is not that common. No code where duplicated call would cause a considerable overhead or harmful side-effects was found during the review, so '''the "inefficiency issues" are really non-issues''' and listed below only for reference.
+
+=== Errors due to incomplete initialization ===
+
+Incomplete initialization problem is the following:
+{{{
+foo = []
+
+1. thread 1: if not foo: true, needs initializing
+2. thread 1: foo.append(x)
+3. thread 2: if not foo: false, does not need initializing --> use the incomplete foo
+4. thread 1: foo.append(y)
+5. thread 2: use fully initialized foo
+}}}
+
+Incomplete initialization errors can generally be avoided by using full assignment instead of elementwise modification; additionally, to make sure no further modifications of a list can happen, tuples should be used instead of lists (inspired by source:django/trunk/django/template/context.py#L86):
 
 '''BAD'''
@@ -58 +73 @@
       foo = tuple(tmp) # assignment is "atomic", tuple is const-correct and more efficient
 }}}
+
+There is at least one location in code that uses the "bad" algorithm.
 
 === Modules' use of globals ===