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/20190729121745.GA140682@xxxxxxxxxx > > Suggested-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> > --- > 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 <stern@xxxxxxxxxxxxxxxxxxx>
