Re: [msysGit] Re: [PATCH/RFC] mingw: implement PTHREAD_MUTEX_INITIALIZER
Am 25.10.2011 22:51, schrieb Erik Faye-Lund:
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> On Tue, Oct 25, 2011 at 10:07 PM, Johannes Sixt <j6t@kdbg.org> wrote:
>> HOWEVER, when it continues, there is NO [*] guarantee that it will also
>> see the values that InitializeCriticalSection() has written, because
>> there were no memory barriers involved. When it continues, there is a
>> chance that it calls EnterCriticalSection() with uninitialized values!
>>
>
> Thanks for pointing this out, I completely forgot about write re-ordering.
>
> This is indeed a problem. So, shouldn't replacing "mutex->autoinit =
> 0;" with "InterlockedExchange(&mutex->autoinit, 0)" solve the problem?
> InterlockedExchange generates a full memory barrier:
> http://msdn.microsoft.com/en-us/library/windows/desktop/ms683590(v=vs.85).aspx
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>> [*] If you compile this code with MSVC >= 2005, "No guarantee" is not
>> true, it's exactly the opposite because Microsoft extended the meaning
>> of 'volatile' to imply a memory barriere.
>
> Do you have a source for this? I'm not saying it isn't true, I just
> never heard of this, and would like to read up on it :)
http://msdn.microsoft.com/en-us/library/ms686355%28VS.85%29.aspx
-- Hannes
Johannes Sixt <j6t@kdbg.org>