Subj : Re: Memory visibility and MS Interlocked instructions
To   : comp.programming.threads
From : Alexander Terekhov
Date : Thu Aug 25 2005 08:38 pm


Scott Meyers wrote:

[... busted CacheComputedValue()/FetchComputedValue() example ...]

   atomic<int> iValue;
   atomic<BOOL> fValueHasBeenComputed(FALSE);
   int ComputeValue();
   // http://tinyurl.com/68jav
   #pragma isolated_call(ComputeValue)

   void CacheComputedValue()
   {
     if (!fValueHasBeenComputed.load(msync::naked_competing)) 
     {
       iValue.store(ComputeValue(), msync::naked_competing);
       fValueHasBeenComputed.store(TRUE, msync::ssb);
     }
   }

   BOOL FetchComputedValue(int *piResult)
   {
     if (fValueHasBeenComputed.load(msync::cchlb_true)) 
     {
       *piResult = iValue.load(msync::naked_competing);
       return TRUE;
     } 
     else 
       return FALSE;
   }

To Peter: I've extended cc* stuff with path specific variants so
that you can give compiler a hint on which path you don't really
need isync.

regards,
alexander.

.