On Sat, Aug 23, 2014 at 11:01:01AM -0700, Randy Dunlap wrote:
> On 08/22/14 23:05, Ganesh Rapolu wrote:
> > In the first example in the memory-barriers.txt file, CPU 2 is assigned to
> > run (x = B; y = A;). However, the rest of the example proceeds as if CPU 2 had been
> > running (x = A; y = B;) as shown by the descriptions of the possible executions:
> >
> > STORE A=3, STORE B=4, x=LOAD A->3, y=LOAD B->4
> > STORE A=3, STORE B=4, y=LOAD B->4, x=LOAD A->3
> > STORE A=3, x=LOAD A->3, STORE B=4, y=LOAD B->4
> > STORE A=3, x=LOAD A->3, y=LOAD B->2, STORE B=4
> > STORE A=3, y=LOAD B->2, STORE B=4, x=LOAD A->3
> > STORE A=3, y=LOAD B->2, x=LOAD A->3, STORE B=4
> > STORE B=4, STORE A=3, x=LOAD A->3, y=LOAD B->4
> > STORE B=4, ...
> > ...
> >
> > The change was merely to make the inital evironment consistent with what happens in the
> > rest of the example.
> >
> > Signed-off-by: Ganesh Rapolu <ganesh.rapolu@xxxxxxxxxxx>
>
>
> Comments David, Alexey, Andrew, Paul?
>
> This would revert Alexey's patch 615cc2c9cf9529846fbc342560d6787c2ccaaeea:
> "Documentation/memory-barriers.txt: fix important typo re memory barriers"
> that was merged on June 6, 2014.
>
> Thanks.
>
>
> > ---
> > Documentation/memory-barriers.txt | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
> > index a4de88f..9a46bbe 100644
> > --- a/Documentation/memory-barriers.txt
> > +++ b/Documentation/memory-barriers.txt
> > @@ -115,8 +115,8 @@ For example, consider the following sequence of events:
> > CPU 1 CPU 2
> > =============== ===============
> > { A == 1; B == 2 }
> > - A = 3; x = B;
> > - B = 4; y = A;
> > + A = 3; x = A;
> > + B = 4; y = B;
Alexey's patch was correct as far as it went, but it was incomplete.
(Read his commit log for more information.)
Would either of you like to send a patch fixing up the combinations?
Thanx, Paul
> > The set of accesses as seen by the memory system in the middle can be arranged
> > in 24 different combinations:
> >
>
>
> --
> ~Randy
>
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