[Cbe-oss-dev] [PATCH 2:9] spufs: Fix spu status read in spu_stopped()

[Benjamin Herrenschmidt]

On Wed, 2008-06-04 at 13:29 +0000, Luke Browning wrote:
> On Wed, 2008-06-04 at 11:49 +0800, Jeremy Kerr wrote:
> > Hi Luke,
> > 
> > > +	/* Ensure that all spu status bits have been updated */
> > > +	eieio();
> > > +
> > > +top:
> > > +	*stat = ctx->ops->status_read(ctx);
> > 
> > should the eieio() be repeated for each status read? (ie, have the top: 
> > label before the eieio)
> 
> No.  eieio() must be reliable.  Otherwise it is worthless.

Ugh ?

What do you mean ?

If you needed that eieio at all in the first place, then yes, you
would probably need it only once, but this has nothing to do with
being "reliable" :-) It's purely due to the fact that the loop isn't
doing any relevant operations that might be re-ordered with that load,
and so subsequent loads from the same place don't need another eieio.

However, I strongly suspect that status_read implementation uses
one of the in_* accessors which will already do the necessary barrier.

Ben.