Subj : Re: [.NET] Volatile Fields [correction]
To   : comp.programming.threads
From : Joe Seigh
Date : Tue Sep 20 2005 10:54 am

David Hopwood wrote:
> Joe Seigh wrote:
>>
>>You don't need the load on the "memory barrier".
>>
>>W = X = Y = Z = 0;
>>
>>Processor 1:   W = 1; L = 1; X = 1
>>Processor 2:   if (X == 1) { Y = 1; L = 1; Z = 1; }
>>Processor 3:   if (Z == 1) { assert (W == 1 && Y == 1); }
>>
>>W and Y are stored by two different processors and are seen in order.
> 
> 
> What are the stores to L for?
> 
>   W = X = Y = Z = 0;
> 
>   Processor 1:   W = 1; X = 1;
>   Processor 2:   if (X == 1) { Y = 1; Z = 1; }
>   Processor 3:   if (Z == 1) { assert (W == 1 && Y == 1); }
> 
> cannot fail the assert (for processor consistency / x86 WB / .NET with volatiles).
> 

W and Y are stores by two different processors.  Under processor consistency you
aren't guaranteed to see them in order.  And I'm talking about processor
consistency w/o .NET volatiles.

-- 
Joe Seigh

When you get lemons, you make lemonade.
When you get hardware, you make software.

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