Hi Akira,
On Sun, 24 Sep 2023 09:02:53 +0900 Akira Yokosawa <akiyks@xxxxxxxxx> wrote:
> Hi,
>
> On 2023/09/24 1:32, SeongJae Park wrote:
> > From: SeongJae Park <sj38.park@xxxxxxxxx>
> >
> > memorder.tex explains READ_ONCE() is having smp_mb(), but the following
> > quick quizz asks why it has mb() instead of rmb(). Fix the wrong names
> > in the quick quizz.
> >
> > Signed-off-by: SeongJae Park <sj38.park@xxxxxxxxx>
> > ---
> > memorder/memorder.tex | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/memorder/memorder.tex b/memorder/memorder.tex
> > index 5c978fbe..b3acc14a 100644
> > --- a/memorder/memorder.tex
> > +++ b/memorder/memorder.tex
> > @@ -5491,7 +5491,7 @@ Alpha is the only CPU whose \co{READ_ONCE()} includes an \co{smp_mb()}.
> > \QuickQuizSeries{%
> > \QuickQuizB{
> > Why does Alpha's \co{READ_ONCE()} include an
> > - \co{mb()} rather than \co{rmb()}?
> > + \co{smp_mb()} rather than \co{smp_rmb()}?
>
> Definition in Linux kernel's arch/alpha/include/asm/rwonce.h reads:
>
> #define __READ_ONCE(x) \
> ({ \
> __unqual_scalar_typeof(x) __x = \
> (*(volatile typeof(__x) *)(&(x))); \
> mb(); \
> (typeof(x))__x; \
> })
>
> So I don't think this change is needed.
>
> As this quiz is talking about Alpha ISA, how about rewording the
> quiz to:
>
> Why does Alpha's \co{READ_ONCE()} include an
> \co{mb} instruction rather than a \co{rmb}?
>
> Thanks, Akira
>
> > }\QuickQuizAnswerB{
> > Alpha has only \co{mb} and \co{wmb} instructions,
> > so \co{smp_rmb()} would be implemented by the Alpha \co{mb}
> > --
> > 2.17.1
That makes sense. Thank you for nice review and suggestion! I will make the
second version of this patch following your comment.
Thanks,
SJ
