Subj : Re: sync vs. eieio on powerpc
To   : comp.programming.threads
From : Alexander Terekhov
Date : Tue Mar 01 2005 01:07 pm


Joe Seigh wrote:
> 
> On Tue, 01 Mar 2005 12:04:10 +0100, Alexander Terekhov <terekhov@web.de> wrote:
> 
> >
> > Joe Seigh wrote:
> > [...]
> >> I'm guessing isync is "load/load" and "load/store".
> >
> > I think that in sparc terms, it is more proper to view it as
> > store/load and store/store in conjunction with successful store
> > conditional.
> >
> Actually, only in conjunction with a load reserved/store conditional
> on the same memory location.  

Store conditional simply works in conjunction with load reserved.

>                               And some pretty specific overall logic
> at that. 

I.e reservation and branching.

 
>          In general, it's incorrect to characterize it as an acquire
> with anything but a prior load.


Nope. You can have ordinary loads in between LR and SC+isync. They 
are unordered (data and control dependencies aside for a moment). And 
think of moving isync above SC (which is a store, not a load).

regards,
alexander.

.