On Mon, Jul 29, 2019 at 04:41:34PM -0400, Alan Stern wrote:
> On Mon, 29 Jul 2019, Joel Fernandes (Google) wrote:
>
> > To reduce ambiguity in the more exotic ->prop ordering example, let us
> > use the term cumul-fence instead fence for the 2 fences, so that the
> > implict ->rfe on loads/stores to Y are covered by the description.
> >
> > Link: https://lore.kernel.org/lkml/[email protected]
> >
> > Suggested-by: Alan Stern <[email protected]>
> > Signed-off-by: Joel Fernandes (Google) <[email protected]>
> > ---
> > tools/memory-model/Documentation/explanation.txt | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/memory-model/Documentation/explanation.txt
> > b/tools/memory-model/Documentation/explanation.txt
> > index 68caa9a976d0..634dc6db26c4 100644
> > --- a/tools/memory-model/Documentation/explanation.txt
> > +++ b/tools/memory-model/Documentation/explanation.txt
> > @@ -1302,7 +1302,7 @@ followed by an arbitrary number of cumul-fence links,
> > ending with an
> > rfe link. You can concoct more exotic examples, containing more than
> > one fence, although this quickly leads to diminishing returns in terms
> > of complexity. For instance, here's an example containing a coe link
> > -followed by two fences and an rfe link, utilizing the fact that
> > +followed by two cumul-fences and an rfe link, utilizing the fact that
> > release fences are A-cumulative:
> >
> > int x, y, z;
> > @@ -1334,10 +1334,10 @@ If x = 2, r0 = 1, and r2 = 1 after this code runs
> > then there is a prop
> > link from P0's store to its load. This is because P0's store gets
> > overwritten by P1's store since x = 2 at the end (a coe link), the
> > smp_wmb() ensures that P1's store to x propagates to P2 before the
> > -store to y does (the first fence), the store to y propagates to P2
> > +store to y does (the first cumul-fence), the store to y propagates to P2
> > before P2's load and store execute, P2's smp_store_release()
> > guarantees that the stores to x and y both propagate to P0 before the
> > -store to z does (the second fence), and P0's load executes after the
> > +store to z does (the second cumul-fence), and P0's load executes after the
> > store to z has propagated to P0 (an rfe link).
> >
> > In summary, the fact that the hb relation links memory access events
>
> Acked-by: Alan Stern <[email protected]>
Queued with Alan's ack, thank you both!
Thanx, Paul
