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Date: Mon, 24 Sep 2012 23:50:00 -0400
Message-ID: 
 <CALdE9OA5anbAP3UHMUvL70GOxuFrfYkni0eR7jY_-mg3B-hJfg@mail.gmail.com>
Subject: Re: STDCXX-1056 : numpunct fix
From: Stefan Teleman <stefan.teleman@gmail.com>
To: "Apache Standard C++ Library" <dev@stdcxx.apache.org>
Content-Type: text/plain; charset=UTF-8

On Mon, Sep 24, 2012 at 10:03 PM, Martin Sebor <msebor@gmail.com> wrote:
> FWIW, there are race conditions in stdcxx. Some of them are by
> design and benign on the systems the library runs on (although
> I acknowledge that some others may be bugs). One such benign
> date race is:
>
>   time    T1      T2
>     0    x = N
>     1    x = N   read x
>
> where x is a scalar that can be accessed atomically by the CPU
> and the compiler.
>
> I think some of the lazy facet initialization falls under this
> class. It would be nice to fix them but only if it doesn't slow
> things down. The others need to be fixed in any case.

The race conditions I am talking about are not benign.

I've uploaded a full thread analyzer output for 22.locale.numpunct.mt
showing dataraces here:

http://s247136804.onlinehome.us/stdcxx-1056-malign/22.locale.numpunct.mt.2.er.tar.bz2

The name of the analyzer results directory is 22.locale.numpunct.mt.2.er

You will need the SunPro Linux 12.3 Thread Analyzer installed, which
comes with SunPro anyway. The analyzer itself is
${PATH_TO_SUN_PRO_INSTALL}/bin/analyzer

There's a screenshot from the same Analyzer output here:

 http://s247136804.onlinehome.us/stdcxx-1056-malign/sunpro_thread_analyzer_screenshot.jpg

taken just now on my laptop. The report itself is from a couple of
days ago, and it's from a run with only the _numpunct.h patch applied.
No patches to either facet.cpp, punct.cpp or locale_body.cpp.

It shows the types of race conditions it's reporting: these are
read/write race conditions, not read/read. The thread analyzer's html
filter doesn't show the types of races reported as clearly as the
command-line analyzer which has a windowing GUI.

At any rate you can see the same exact type of race conditions being
reported by the Intel Inspector 2013 Thread Analyzer.

-- 
Stefan Teleman
KDE e.V.
stefan.teleman@gmail.com