Subj : Re: Boost.Threads on its way to C++0x
To   : comp.programming.threads
From : Torsten Robitzki
Date : Wed Apr 27 2005 07:40 pm

gottlobfrege@gmail.com wrote:

> 
>    void ensure_initted()
>    {
>       if (!AtomicExchange(&started, true))
>       {
>          InitCriticalSection(&cs);
>          AtomicExchange(&initted, true);
> 	}
> 	else
> 	{
>          // There's better ways to do this than spinning,
>          // but this is make the example shorter.
>          // In fact, this example has a starvation problem,
>          // if this thread has a higher priority
>          // than the init thread.
>          // (ie may never get a chance to be initted)
> 
>          while (!AtomicRead(&initted))
>          {
>              Sleep(1);
>          }
>       }
>    }

When a first thread executes the first call to AtomicExchange() every 
other thread will leave the function immediately after the call to this 
function without ensuring that the first thread finished the call to 
InitCriticalSection(). So the call to EnterCriticalSection() can operate 
on an unitialized cs.

regards
Torsten

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