Subj : Re: Memory Barriers, Compiler Optimizations, etc.
To   : comp.programming.threads
From : Joseph Seigh
Date : Mon Feb 07 2005 03:53 pm

On Mon, 7 Feb 2005 11:41:18 -0800, SenderX <xxx@xxx.com> wrote:

>> > Here are some questions that need clarification in your documentation:
>> >
>> > 1. Can external data depend on the return value from a failed CAS?
>>
>> I don't undestand what your asking.
>
> static CMyData my_data;
> static volatile LONG flag = 0;
>
>
> my_data.setup();
> InterlockedCompareExchange( &flag, 1, 0 );
>
>
> AnotherConcurrentThread
> ------------------
>
> while ( ! InterlockedCompareExchange( &flag, 0, 0 ) ) { Sleep( 0 ); _asm
> pause; }
> // flag is set
> my_data.use();
>
>
>
> Is this safe?
>
>
   while (flag != 1)
	sleep(0);
   InterlockedCompareExchange(&flag, 1, 1);

would be better.  DCL would be a less contrived example of
the usage you're trying to show, e.g. initFreeQueue here

http://groups-beta.google.com/group/comp.programming.threads/msg/31803c3398658e06


Microsoft should just say that their synchronization functions
"synchronize" memory and not bother to define memory synchronization
which Posix doesn't bother to define either. :)


-- 
Joe Seigh

.