Subj : Re: Memory visibility and MS Interlocked instructions
To   : comp.programming.threads
From : Alexander Terekhov
Date : Sun Sep 04 2005 12:20 am



Peter Dimov wrote:
[...]
> > P1: X = 1; Y = 1;
> > P2: if( Y == 1) { Z = 1; }
> > P3: if( Z == 1) { assert( X == 1 ); }
> >
> > Z == 1 && X != 1 is false.
> 
> Great. But
> 
> P1: Y = 1;
> P2: if( Y == 1 ) { Z = 1; }
> P3: if( Z == 1 ) { assert( Y == 1 ); }
> 
> may assert. This still breaks happens-before; there is a similar Y = 1

Y = 1 (and Z = 1) are writes "in progress". 

> << Y == 1 << Z = 1 << Z == 1 << (other) Y == 1 chain.

P1: Y = 1; Y = 2;
P2: if( Y == 2 ) { Z = 1; }
P3: if( Z == 1 ) { assert( Y >= 1 ); }

regards,
alexander.

.