Hi, all > Motohiro, do you mind if I submit patches to Paul on behalf of Certainly, please submit patches. While I was working on Japanese translation, I felt something odd with this smp_mb sample code, but I did not report one to upstream because I was not so sure. I just left a comment on my translation. It is my great pleasure that someone reads my translation so seriously, Akira. Thanks again for great book, Paul and others! -- Motohiro Kanda 2020-12-02 23:50 GMT+09:00, Akira Yokosawa <akiyks@xxxxxxxxx>: > From 89ab8426f9821b6a8bf86e9d4f7eb596e0cfed73 Mon Sep 17 00:00:00 2001 > From: Akira Yokosawa <akiyks@xxxxxxxxx> > Date: Wed, 2 Dec 2020 07:35:08 +0900 > Subject: [PATCH -perfbook] whymb: Fix description of compiler mischief > > In this code snippet, the assertion can not fire due to different > reasons. > When bar() observes b == 1, the smp_mb() assures a == 1. > When bar() observes b == 0, the while loop will loop forever and > the assertion can't be reached. > > This was pointed out by Motohiro Kanda in his Japanese translation > of perfbook [1]. > > [1]: > https://sites.google.com/site/kandamotohiro/perfbook-d/perfbookappendixf10 > > Cc: Motohiro Kanda <kanda.motohiro@xxxxxxxxx> > Signed-off-by: Akira Yokosawa <akiyks@xxxxxxxxx> > --- > Hi Paul, > > (Cc: Motohiro) > > Looks like this inconsistency in the Answer to Quick Quiz has > been Motohiro's translation note for quite a while. > (since 2017?) > > He contributed to perfbook in the past. There is a couple of > commits with his Reported-by. > > Motohiro, do you mind if I submit patches to Paul on behalf of > you like this? > > And I think Paul is likely to do some wordsmithing on top of > this patch. ;-) > > Thanks, Akira > -- > appendix/whymb/whymemorybarriers.tex | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/appendix/whymb/whymemorybarriers.tex > b/appendix/whymb/whymemorybarriers.tex > index dff7fafc..301342f3 100644 > --- a/appendix/whymb/whymemorybarriers.tex > +++ b/appendix/whymb/whymemorybarriers.tex > @@ -1152,7 +1152,10 @@ void bar(void) > } > \end{VerbatimN} > > - Given this optimization, the assertion could clearly fire. > + Given this optimization, the code would behave in a completely > + different way than the original intention. > + If \co{bar()} observed \qco{b == 0}, the assertion could not > + be reached due to the infinite loop. > You should use volatile casts or (where available) C++ > relaxed atomics to prevent the compiler from optimizing > your parallel code into oblivion. > -- > 2.17.1 > >
