|
|
Boost-Commit : |
From: bdawes_at_[hidden]
Date: 2008-04-27 20:18:48
Author: bemandawes
Date: 2008-04-27 20:18:48 EDT (Sun, 27 Apr 2008)
New Revision: 44828
URL: http://svn.boost.org/trac/boost/changeset/44828
Log:
Added Jeffrey to author list, moved ref to his paper to the references section, struck ack section, added the tentative wording to cover concurrent modification of different element's contents.
Text files modified:
sandbox/committee/LWG/thread_safety.html | 43 ++++++++++++++++++++++++++++-----------
1 files changed, 31 insertions(+), 12 deletions(-)
Modified: sandbox/committee/LWG/thread_safety.html
==============================================================================
--- sandbox/committee/LWG/thread_safety.html (original)
+++ sandbox/committee/LWG/thread_safety.html 2008-04-27 20:18:48 EDT (Sun, 27 Apr 2008)
@@ -13,7 +13,7 @@
<p><span style="background-color: rgb(255, 255, 0)">Doc. no.
D2603=08-0113</span><br>
Date:
-<!--webbot bot="Timestamp" s-type="EDITED" s-format="%Y-%m-%d" startspan -->2008-04-25<!--webbot bot="Timestamp" endspan i-checksum="12286" --><br>
+<!--webbot bot="Timestamp" s-type="EDITED" s-format="%Y-%m-%d" startspan -->2008-04-27<!--webbot bot="Timestamp" endspan i-checksum="12290" --><br>
Project: Programming Language C++<br>
Reply to: Beman Dawes <bdawes at acm.org><br>
@@ -23,7 +23,8 @@
Hans Boehm <Hans.Boehm at hp.com><br>
Lawrence Crowl <crowl at google.com><br>
Paul E. McKenney <paulmck at linux.vnet.ibm.com><span style="background-color: rgb(255, 255, 0)"><br>
- </span></p>
+</span>
+Jeffrey Yasskin <jyasskin at google.com></p>
<h1>Thread-Safety in the Standard Library (Rev 2)</h1>
@@ -32,7 +33,6 @@
<a href="#Rationale">Rationale</a><br>
<a href="#Existing-practice">Existing practice</a><br>
<a href="#Proposed-Wording">Proposed wording</a><br>
-Acknowledgements<br>
<a href="#Revision-history">Revision history</a><br>
<a href="#References">References</a></p>
@@ -149,7 +149,7 @@
non-const arguments, including *this, directly or indirectly point to or
reference objects of a standard library type shared between the threads, and
one call does not happen before the other ([Multi-threaded executions and data
- races]).</u><b>[Editorial note: Technically, there are no non-const arguments.]</b></font></p>
+ races]).</u></font><b><span style="background-color: #FFFF00">[Editorial note: Technically, there are no non-const arguments.]</span></b></p>
<p><i>[Note: </i>This <font color="#FF0000"><strike>lack of strong thread-safety guarantee</strike></font>
<u><font color="#228822">prohibition against concurrent non-const access</font></u> means that
modifying an object of a standard library type shared between threads
@@ -206,6 +206,27 @@
locale object per thread. If there is a single global locale object for the
entire program, it is not required to be thread-safe ([res.on.thread.safety]).</font></u></p>
</blockquote>
+ <p><i>At a location in 23 to be determined by the project editor, add a new paragraph:</i></p>
+ <blockquote>
+ <p><u><font color="#228822">For purposes of determining thread-safety requirements ([res.on.thread.safety[),
+ implementations shall consider the following functions to be const:<code>
+ begin</code>, <code>end</code>, <code>rbegin</code>, <code>rend</code>, <code>
+ front</code>, <code>back</code>, <code>data</code>, <code>find</code>, <code>
+ lower_bound</code>, <code>upper_bound</code>, <code>equal_range</code>, and,
+ except in associative containers, <code>operator[]</code>.</font></u></p>
+ </blockquote>
+ <p><i><span style="background-color: #FFFF00">Somewhere</span>, add:</i></p>
+ <blockquote>
+ <p><font color="#228822">Notwithstanding ([res.on.thread.safety[), implementations are required to
+ avoid data races when the contents of the contained object in different elements in the same sequence are modified
+ concurrently.</font></p>
+ <p><font color="#228822"><i>[Example: </i>For a <code>vector<int> x
+ </code>with a size greater than one, <code>x[1] = 5</code>
+ and <code>*x.begin() = 10</code> can be executed concurrently without a data race, but
+ <code>x[0]
+ = 5</code> and <code>*x.begin() = 10</code> executed concurrently may result in a data race. <i>--
+ end example]</i></font></p>
+ </blockquote>
<p><i>Change 26.7 C Library [c.math] paragraph 6 as indicated:</i></p>
<blockquote>
<p>The <code>rand</code> function has the semantics specified in the C
@@ -217,10 +238,6 @@
but not required to provide such thread-safety. Calls to <code>rand</code>
from other library functions shall not result in data races.</u></font></p>
</blockquote>
- <h2><a name="Acknowledgements">Acknowledgements</a></h2>
- <p><font color="#228822"><u>Jeffrey Yasskin's, N2519 <i>Library thread-safety
- from a user's point of view, with wording</i> provided several valuable
- insights that have been reflected in this proposal.</u></font></p>
<h2><a name="Revision-history">Revision history</a></h2>
<p>N2603 - Revision 2:</p>
<ul>
@@ -255,13 +272,15 @@
N2334</a>, Concurrency memory model (revised again), Clark Nelson and Hans-J.
Boehm</p>
<p>
+ <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2519.html">
+ N2519</a>, Library thread-safety
+ from a user's point of view, with wording, Jeffrey Yasskin</p>
+ <p>
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1947.pdf">
N1947</a>, The Memory Model and the C++ Library, Non-Memory Actions etc., Nick
Maclaren</p>
<hr>
- <p> </p>
-<p> </p>
-
+
</body>
-</html>
+</html>
\ No newline at end of file
Boost-Commit list run by bdawes at acm.org, david.abrahams at rcn.com, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk